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HE IS THE FIRST, HE IS THE LAST
HE IS THE MANIFEST, HE IS THE HIDDEN, &
HE KNOWS EVERYTHING HE BRINGS THE NIGHT INTO THE DAY, &
BRINGS THE DAY INTO THE NIGHT, & HE KNOWS THE THOUGHTS OF THE
HEARTS S.AL-HADID-385 (AL-QURAN)
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Fruit quality and storability of Kinnow mandarin (Citrus reticulata Blanco) in relation to tree age
BY
SAMINA KHALID M.Sc. (Hons.) Horticulture
2007-ag-09
A thesis submitted in the fulfillment of
the requirements for the degree of
Doctor of Philosophy
in
Horticulture
Institute of Horticultural Sciences Faculty of Agriculture
UNIVERSITY OF AGRICULTURE, FAISALABAD PUNJAB, PAKISTAN
2013
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To The Controller of Examinations University of Agriculture
Faisalabad
We, the supervisory committee, certify that the contents and form of this thesis
submitted by Miss Samina Khalid Regd. No. 2007-ag-09, have been found satisfactory, and recommend it to be processed for evaluation by the external examiner(s) for the
award of the degree.
SUPERVISORY COMMITTEE
1) SUPERVISOR:
_________________________________ (PROF. DR. AMAN ULLAH MALIK)
2) MEMBER: __________________________________
(DR. AHMAD SATTAR KHAN)
3) MEMBER: __________________________________
(DR. AMER JAMIL)
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ACKNOWLEDGEMENTS
Each and every praise is due to Almighty Allah, the omnipotent and benefactor, “Who taught Adam the names of all the things”, and “He taught man that which he knew not”. All the blessings upon Holy Prophet (P.B.U.H) who conveyed Allah’s message with full devotion.
Special thanks are due to my supervisor Prof. Dr. Aman Ullah Malik for his invaluable advice, encouragement and support at every step of my PhD studies. Achieving this degree would not have been possible without his support. My gratitude is also for Dr. Ahmad Sattar Khan, Institute of Horticultural Sciences, University of Agriculture, Faisalabad and Dr. Amer Jamil, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Agriculture, Faisalabad whose knowledge and comments contributed significantly to attaining this goal.
I would like to acknowledge the support of my parent Department Institute of Horticultural Sciences, UAF, its staff and Director. I am also thankful for the assistance and support provided by Dr. Saeed Ahmad and his Staff (Shakil Zahid, Shakil Latif and Farhan) at Pomology Laboratory, Institute of Horticultural Sciences, University of Agriculture, Faisalabad, for providing facilities of macro-nutrient analysis.
Sincere thanks are extended to Dr. Muhammad Zargham Khan Chairman/Professor, Department of Pathology, Faculty of Veterinary Science, University of Agriculture, Faisalabad, his students and laboratory staff for their valuable guidance during anatomical studies. Special thanks to Dr. Muhammad Shahid Assistant Professor, Department of Chemistry and Biochemistry, Faculty of Sciences, for his support in antioxidant and phenolics determination. I am also grateful to Mr. Abdul Qudoos Research Officer, Central Hi-Tech Laboratory, University of Agriculture, Faisalabad, for his assistance in micro-nutrient analysis.
I am also thankful to Prof. Dr. Zora Singh, Department of Environment and Agriculture, School of Science, Faculty of Science and Engineering, Curtin University, Western Australia for his kind guidance and support during my six months training at Australia, under International Research Support Initiative Programme (IRSIP), Programe of Higher education Commission (HEC).
I gratefully acknowledge the help of Dr. Basharat Ali Saleem, Assistant Director Fruit and Vegetable Development Project, Punjab Agriculture Department during the course of my PhD studies. I would like to thank Mr. Tariq Mehmood Cheema, Kinnow mandarin grower at Chack No. 99 NB, Sargodha for his assistance and hospitality.
I am also thankfull to my lab fellows Muhammad Shafique Khalid, Kashif Razzaq, Sami Ullah, Muhammad Shafique, Muhammad Amin, Mudassar Naseer, Omer Hafeez Malik, Munaza Saeed, Habat Ullah Asad and Syed Ali Raza, for their cooperation in an excellent working atmosphere during my research work. I want to express my great appreciation, sincerest gratitude and special thanks to the lab staff including Miss Rabia Hameed, Abdul Haseeb, Muhammad Afzal, and Javed Maseeh for their assistance in laboratory work.
I am gratefull to Higher Education Commission (HEC), Islamabad, Pakistan, for awarding me scholarship under Indigenous 5000 PhD Fellowship scheme and six months research fellowship under International Research Support Initiative Programme (IRSIP) to conduct a part of my PhD research at Curtin University, Perth Western Australia.
I also express my gratitude to my friends for their help and cooperation during my PhD studies.
Last and most important I would like to thank my family for their patience, encouragement and financial support during my studies. I am also grateful to all those whom I mentioned or could not mention here but they helped me positively.
(Samina Khalid)
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TABLE OF CONTENTS
Chapter
Title Page
Acknowledgements i Table of contents ii List of tables vii List of figures x List of symbols and abbreviations xii ABSTRACT 1 1 GENERAL INTRODUCTION 3 2 GENERAL REVIEW OF LITERATURE 6 2.1 Introduction 6 2.2 Origin and Distribution 6 2.3 Citrus Industry of the World 7 2.3.1 World Mandarin and Tangerine Production 8 2.3.2 World Mandarin and Tangerine Export 8 2.4 Citrus Industry of Pakistan 9 2.4.1 Mandarin export from Pakistan 9 2.5 Citrus Fruit Anatomy 10 2.6. Fruit Growth and Development 10 2.7 Fruit Quality 11 2.7.1 Factors affecting fruit quality 11 2.7.1.1 Tree age 11 2.7.1.1.1 Physical fruit quality 11 2.7.1.1.2 Biochemical fruit quality 12 2.7.1.2 Fruit size 12 2.7.1.2.1 Physical fruit quality 12 2.7.1.2.2 Biochemical fruit quality 13 2.7.1.3 Canopy position 14 2.7.1.3.1 Physical fruit quality 14 2.7.1.3.2 Biochemical fruit quality 14 2.7.1.4 Plant growth regulators 16 2.7.1.4.1 Physical fruit quality 17 2.7.1.4.2 Biochemical fruit quality 20 2.7.1.5 Mineral nutrition 21 2.7.1.5.1 Physical fruit quality 23 2.7.1.5.2 Biochemical fruit quality 24 3 GENERAL MATERIALS AND METHODS 26 3.1 Plant material 26 3.2 Physical fruit quality 27 3.2.1 Fruit colour (score) 27 3.2.2 Fruit smoothness (score) 27 3.2.3 Fruit softness (score) 27 3.2.4 Fruit mass (g) 27 3.2.5 Fruit diameter (mm) 27 3.2.6 Fruit mass loss (%) 27 3.2.7 Rind thickness (mm) 27
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Chapter
Title Page
3.2.8 Rind mass (%) 27 3.2.9 Rag mass (%) 28 3.2.10 Seed mass (%) 28 3.2.11 Seed number 28 3.2.12 Healthy seed (%) 28 3.2.13 Aborted seed (%) 28 3.2.14 Juice mass (%) 28 3.3 Biochemical fruit quality 29 3.3.1 pH 29 3.3.2 TSS (°Brix) 29 3.3.3 Titratable acidity (TA) (%) 29 3.3.4 Ascorbic acid (AA) (mg 100 mL-1) 29 3.3.5 Sugars (reducing, non reducing and total sugars) 29 3.4 Statistical Analysis 29 4 EFFECT OF TREE AGE AND FRUIT CANOPY
POSITION ON FRUIT QUALITY OF 'KINNOW' MANDARIN
30
4.1 Introduction 30 4.2 Materials and Methods 32 4.2.1 Plant material and site selection 32 4.2.2 Physical fruit quality 32 4.2.3 Biochemical fruit quality 32 4.2.4 Nutrient analysis 33 4.2.4.1 Fruit sample preparation 33 4.2.4.2 Nitrogen (N) 33 4.2.4.3 Estimation of elements other than N 34 4.2.4.3.1 Phosphorous (P) 34 4.2.4.3.2 Potassium (K) 34 4.2.4.3.3 Calcium (Ca) and micronutrients 34 4.2.5 Statistical analysis 35 4.3 Results 35 4.3.1 Physical fruit quality 35 4.3.2 Biochemical fruit quality 35 4.3.3 Rind macro-nutrient concentrations 39 4.3.4 Rind micro-nutrient concentrations 39 4.3.5 Correlation between rind nutrient concentrations and
rind quality 39
4.3.6 Correlation between rind nutrient concentrations and internal fruit quality
41
4.4 Discussion 41 5 EFFECT OF TREE AGE AND FRUIT SIZE ON
STORAGE POTENTIAL OF 'KINNOW' MANDARIN
48
5.1 Introduction 48 5.2 Materials and methods 49
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Chapter
Title Page
5.2.1 Plant material and site selection 49 5.2.2 Influence of tree age and fruit size on shelflife of
'Kinnow' mandarin 49
5.2.3 Influence of tree age and fruit size on storage life of 'Kinnow' mandarin
50
5.2.4 Physical fruit quality 50 5.2.4.1 Respiration and ethylene production 50 5.2.5 Biochemical fruit quality 50 5.2.5.5 Total phenolic concentrations (TPC) and antioxidants 50 5.2.6 Statistical analysis 51 5.3 Results 51 5.3.1 Influence of tree age and fruit size on fruit quality of
'Kinnow' mandarin under ambient conditions 51
5.3.1.1 Physical fruit quality 51 5.3.1.2 Biochemical fruit quality 54 5.3.1.3 Respiration and ethylene production during shelflife
studies 61
5.3.2 Influence of tree age and fruit size on storage life of 'Kinnow' mandarin
64
5.3.2.1 Physical fruit quality 64 5.3.2.2 Biochemical fruit quality 66 5.3.2.3 Fruit mass loss (%) during shelflife and storage 78 5.4 Discussion 80 5.4.1 Ambient conditions studies 80 5.4.2 Cold storage studies 82 6 'KINNOW' FRUIT GROWTH AND
DEVELOPMENT IN RELATION TO CHANGES IN ENDOGENOUS LEVELS OF NUTRIENTS AND PECTIN
85
6.1 Introduction 85 6.2 Materials and method 87 6.2.1 Plant material and site selection 87 6.2.2 Fruit diameter (mm) 87 6.2.3 Nutrient analysis 87 6.2.3.1 Leaf sampling and sample preparation 87 6.2.3.2 Nitrogen (N) 88 6.2.3.3 Estimation of elements other than N 88 6.2.4 Pectin analysis 88 6.2.4.1 Alcohol insoluble solids 88 6.2.4.2 Total pectin 88 6.2.4.3 Water soluble pectin 88 6.2.4.4 Pectin determination 89 6.2.5 Anatomical studies 89 6.2.6 Statistical analysis 89 6.3 Results 89
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Chapter
Title Page
6.3.1 Fruit diameter in relation to tree age 89 6.3.2 Cell number and cell size in relation to tree age 90 6.3.3 Nutrient concentrations during fruit growth and
development 91
6.3.3.1 Rind N concentrations 91 6.3.3.2 Rind P concentrations 92 6.3.3.3 Rind K concentrations 92 6.3.3.4 Rag N concentrations 92 6.3.3.5 Rag P concentrations 92 6.3.3.6 Rag K concentrations 92 6.3.3.7 Leaf N concentrations 93 6.3.3.8 Leaf P concentrations 93 6.3.3.9 Leaf K concentrations 93 6.3.4 Pectin concentrations during fruit growth and
development 95
6.3.4.1 Rind total pectin 95 6.3.4.2 Rind water soluble pectin 95 6.3.4.3 Rind protopectin 95 6.3.4.4 Rag total pectin 95 6.3.4.5 Rag water soluble pectin 96 6.3.4.6 Rag protopectin 96 6.3.5 Correlation between leaf nutrient concentrations and
fruit growth and development 96
6.3.6 Correlation between rind nutrients and fruit growth and development
98
6.3.7 Correlation between rag nutrients and fruit growth and development
99
6.4 Discussion 99 7 EFFECT OF TIMING OF PLANT GROWTH
REGULATORS APPLICATION ON FRUIT QUALITY AND STORAGE POTENTIAL OF 'KINNOW' MANDARIN
106
7.1 Introduction 106 7.2 Materials and methods 107 7.2.1 Plant material and site selection 107 7.2.2 Effect of application time of PGRs on shelflife of
'Kinnow' mandarin 108
7.2.3 Effect of application time of PGRs on storage life of 'Kinnow' mandarin
108
7.2.4 Physical fruit quality 108 7.2.5 Biochemical fruit quality 108 7.2.6 Statistical analysis 109 7.3 Results 109 7.3.1 Effect of time of PGRs application on fruit quality of 109 'Kinnow' mandarin during shelf life
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Chapter
Title Page
7.3.1.1 Physical fruit quality 109 7.3.1.2 Biochemical fruit quality 114 7.3.1.3 Fruit mass loss (%) 119 7.3.2 Effect of application time of PGRs on storage life of
'Kinnow' mandarin 120
7.3.2.1 Physical fruit quality 120 7.3.2.2 Biochemical fruit quality 122 7.3.2.3 Fruit mass loss (%) 124 7.4 Discussion 125 8 EXOGENOUS APPLICATIONS OF PGRS AND
NUTRIENT ON FRUIT QUALITY AND STORAGE OF 'KINNOW' MANDARIN
128
8.1 Introduction 128 8.2 Materials and method 129 8.2.1 Plant material and site selection 129 8.2.2 Influence of exogenous applications of plant growth
regulators on fruit quality of young 'Kinnow' mandarin trees
130
8.2.3 Influence of nutrients on fruit quality of young 'Kinnow' mandarin trees
130
8.2.4 Influence of PGRs and nutrients on fruit quality of young 'Kinnow' mandarin trees
131
8.2.5 Physical fruit quality 132 8.2.6 Biochemical fruit quality 132 8.2.7 Statistical analysis 132 8.3 Results 132 8.3.1 Influence of exogenous applications of plant growth
regulators on fruit quality of young 'Kinnow' mandarin trees
132
8.3.1.1 Physical fruit quality 132 8.3.1.2 Biochemical fruit quality 138 8.3.1.3 Discussion 141 8.3.2 Influence of nutrients on fruit quality of young
'Kinnow' mandarin trees 145
8.3.2.1 Physical fruit quality 145 8.3.2.2 Biochemical fruit quality 146 8.3.2.3 Discussion 151 8.3.3 Influence of PGRs and nutrients on fruit quality of
young 'Kinnow' mandarin trees 152
8.3.3.1 Physical fruit quality 152 8.3.3.2 Biochemical fruit quality 159 8.3.3.3 Discussion 162 9 GENERAL CONCLUSION 164 REFERENCES 169 ANNEXURE 193
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LIST OF TABLES
Table Title Page 2.1 Mandarin export from Pakistan during 2008-09 9 4.1 Biochemical characters of 'Kinnow' mandarin fruit in
relation to tree age and canopy position 38
4.2 Biochemical parameters of 'Kinnow' mandarin in relation to tree age and canopy position
38
4.3 Rind nutrient concentrations and rind quality in relation to tree age
42
4.4 Rind macro-nutrients and physical fruit quality of 'Kinnow' mandarin in relation to tree age
43
4.5 Rind micro-nutrients and physical fruit quality of 'Kinnow' mandarin in relation to tree age
44
4.6 Effect of tree age and fruit size on fruit mass (g) of 'Kinnow' mandarin
52
4.7 Effect of tree age, fruit size and shelf duration on physical fruit quality of 'Kinnow' mandarin
52
4.8 Effect of tree age, fruit size and shelf duration influencing biochemical fruit quality of 'Kinnow' mandarin
55
4.9 Influence of tree age, fruit size and shelf duration on total, reducing and non reducing sugar (%) of 'Kinnow' mandarin juice
57
4.10 Influence of tree age, fruit size and shelf duration on AA (mg 100ml-1), TPC (µg ml-1) and AO (mg µl-1) concentrations of 'Kinnow' mandarin juice
59
4.11 Effect of tree age, fruit size and analysis time on rind mass (%) of 'Kinnow' mandarin during storage
66
4.12 Effect of tree age and fruit size on rag mass (%) of 'Kinnow' mandarin fruit during cold storage
67
4.13 Juice mass (%) of 'Kinnow' mandarin fruit affected by tree age and fruit size during cold storage
67
4.14 Effect of tree age and fruit size on TSS (°Brix) of 'Kinnow' mandarin juice during cold storage
70
4.15 Influence of tree age and fruit size on titratable acidity (%) (TA) of 'Kinnow' mandarin juice during cold storage
70
4.16 TSS:TA of 'Kinnow' mandarin juice affected by tree age and fruit size during cold storage
71
4.17 Reducing sugars (%) of 'Kinnow' mandarin juice affected by tree age, fruit size and storage period
73
4.18 Non reducing sugars (%) of 'Kinnow' mandarin juice as affected by tree age, fruit size and storage period
74
4.19 Tree age, fruit size and storage period influencing total sugars (%) of 'Kinnow' mandarin juice
74
4.20 Tree age, fruit size and storage period influencing ascorbic acid concentration (mg 100 ml-1) of 'Kinnow' mandarin juice
76
4.21 Tree age, fruit size and storage period on antioxidant 76
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Table Title Page concentrations of 'Kinnow' mandarin juice
4.22 Total phenolic concentrations (µg ml-1) of 'Kinnow' mandarin juice as influenced by tree age, fruit size and storage period
77
4.23 Correlation between leaf nutrient concentrations and rind cell anatomy, fruit diameter (mm) and pectin concentrations (%)
100
4.24 Correlation between rind nutrient concentrations and rind cell anatomy, fruit diameter (mm) and pectin concentrations (%)
100
4.25 Correlation between rag nutrient concentrations and rind cell anatomy, fruit diameter (mm) and pectin concentrations (%)
101
4.26 Influence of PGRs and shelf duration on physical fruit quality of 'Kinnow' mandarin
110
4.27 Effect of PGRs and shelf duration on physical fruit quality of 'Kinnow' mandarin
112
4.28 Biochemical quality attributes of 'Kinnow' mandarin juice influenced by PGRs and shelf duration
115
4.29 Effect of PGRs and shelf duration on biochemical fruit quality
117
4.30 Effect of PGRs and time of application on mass loss (%) during shelf life of fruit
119
4.31 Effect of PGRs on external fruit quality of 'Kinnow' mandarin during storage
120
4.32 Physical fruit quality of 'Kinnow' mandarin influenced by PGRs during storage
121
4.33 Effect of PGRs on biochemical fruit quality of 'Kinnow' mandarin during storage
123
4.34 Effect of PGRs on biochemical fruit quality of 'Kinnow' mandarin during storage
124
4.35 Influence of PGRs on mass loss (%) during storage 125 4.36 Effect of plant growth regulators on seed quality of
'Kinnow' mandarin 134
4.37 Effect of PGRs on external fruit quality of 'Kinnow' mandarin
135
4.38 Effect of plant growth regulators on internal physical quality of fruit harvested from young 'Kinnow' mandarin trees
137
4.39 Contrast effect on ascorbic acid (mg 100mL-1) of 'Kinnow' mandarin juice
139
4.40 Effect of PGRs applications effect on TSS, titratable acidity (TA) (%) and TSS:TA concentrations of fruit obtained from young 'Kinnow' mandarin trees
140
4.41 Juice total, reducing, and non reducing sugars (%) of young 'Kinnow' mandarin trees as affected by plant growth regulators application
142
4.42 Effect of nutrients on seed quality and quantity variables
145
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Table Title Page 4.43 Effect of nutrients on rind thickness (mm), fruit
diameter (mm) and fruit mass (g) of 'Kinnow' mandarin 145
4.44 Fruit physical quality attributes as affected by nutrient applications
147
4.45 Fruit biochemical variables affected by nutrient application
148
4.46 Effect of nutrients on total, reducing and non reducing sugars (%) of 'Kinnow' mandarin juice
150
4.47 Seed quality parameters influenced by PGRs and nutrients
154
4.48 Fruit physical quality parameters influenced by PGRs and nutrients
155
4.49 Effect of plant growth regulators and nutrients on rind mass (%) of 'Kinnow' mandarin
157
4.50 Influence of plant growth regulators and nutrients on rag mass (%), rind mass (%) and juice mass (%) of 'Kinnow' mandarin
158
4.51 Nutrients and PGRs effect on TSS (Brix) and acidity (%) of 'Kinnow' mandarin juice
160
4.52 Influence of PGRs and nutrients on TSS:TA and ascorbic acid (mg 100ml-1) of 'Kinnow' mandarin juice
163
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LIST OF FIGURES
Figure Title Page
2.1 World mandarin and tangerine production 8 2.2 World mandarin and tangerine export 8 2.3 Citrus area and production in Pakistan 9 2.4 Transverse section of citrus fruit 10 4.1 Effect of tree age and canopy position on rind colour
(score) (a) and rind smoothness score (b) of 'Kinnow' mandarin (n = 40)
35
4.2 Physical fruit quality of 'Kinnow' mandarin affected by tree age and canopy position (n = 40)
37
4.3 Rind macro-nutrient (a, b, c and d) and micro-nutrient (e, f, g and h) concentrations affected by tree age and canopy position (n = 40)
40
4.4 Fruit rind mass (%) (a, d), rag mass (%) (b, e) and juice mass (%) (c, f) influenced by tree age and fruit size during shelflife studies
53
4.5 Effect of tree age and fruit size on TSS (a, d), TA (%) (b, e) and TSS:TA (c, f) of 'Kinnow' mandarin fruit during shelf studies
56
4.6 Influence of tree age and fruit size on total sugars (%) (a, d), reducing sugars (%) (b, c) and non reducing sugars (%) (c, f) of 'Kinnow' mandarin fruit during shelf studies
58
4.7 Tree age and fruit size influenced on AA (mg 100ml-1) (a, d), TPC (µg ml-1) (b, e) and AO (mg µl-1) (c, f) of 'Kinnow' mandarin during seven days shelflife
60
4.8 Effect of tree age and fruit size on CO2 (m Mol kg-1h-1) production during shelflife studies of 'Kinnow' mandarin fruit
62
4.9 Effect of tree age and fruit size on mean CO2 (m Mol kg-1h-1) production during shelflife studies of 'Kinnow' mandarin fruit
62
4.10 Effect of tree age and fruit size on ethylene production (m Mol kg-1h-1) during seven days shelflife studies of 'Kinnow' mandarin fruit
63
4.11 Effect of tree age and fruit size on mean ethylene production (m Mol kg-1h-1) during seven days shelflife studies of 'Kinnow' mandarin
63
4.12 Effect of tree age and storage duration on rind mass (%) (a, d), rag mass (%) (b, e), and juice mass (%) (c, f) of 'Kinnow' mandarin fruit during cold storage
65
4.13 Influence of tree age and storage period on TSS (a, d), TA (%) (b, e) and TSS:TA (c, f) of 'Kinnow' mandarin fruit during cold storage
68
4.14 Effect of tree age and storage duration on reducing sugars (%) (a, d), non reducing sugars (%) (b, e) and total sugars (%) (c, f) of fruit during cold storage
72
4.15 Effect of tree age and fruit size on ascorbic acid (mg 75
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Figure Title Page
100ml-1) (a, d), antioxidant (mg µl-1) (b, e) and total phenolic concentrations (µg ml-1) (c, f) of 'Kinnow' mandarin juice during cold storage
4.16 Influence of tree age and fruit size on fruit mass loss (%) during shelflife studies
78
4.17 Effect of tree age and fruit size on mass loss (%) during cold storage
79
4.18 Effect of tree age and fruit size on mean mass loss (%) during cold storage
79
4.19 Fruit diameter (mm) (a) and increment in diameter (mm) (b) of 'Kinnow' mandarin fruit during fruit growth and development
90
4.20 Rind cell number (cells/mm2) (a) and cell size (mm2) (b) in relation to tree age
91
4.21 Rind, rag and leaf nutrient concentrations in relation to tree age
94
4.22 Influence of tree age on rind total pectin (%) (a), rind water soluble pectin (%) (b) and rind protopectin (%) (c) during fruit growth and development
97
4.23 Influence of tree age on rag total pectin (%) (a), rag water soluble pectin (%) (b) and rag protopectin (%) (c) during fruit growth and development
98
4.24 Effect of PGRs application time and shelf duration on physical fruit quality of 'Kinnow' mandarin
111
4.25 Effect of PGRs application time and shelf duration on rind mass (%) (a,d), rag mass (%) (b,e) and juice mass (%) (c, f) of 'Kinnow' mandarin
113
4.26 Effect of PGRs application time and shelf duration on TSS (°Brix) (a, e), acidity (%) (b, f), TSS:TA ratio (c, g) and ascorbic acid (mg 100 mL-1) (d, h) of 'Kinnow' mandarin
116
4.27 Effect of PGRs application time and shelf duration on reducing sugars (%) (a, d), non reducing sugars (%) (b, e) and total sugars (%) (c, f) of 'Kinnow' mandarin juice
118
4.28 Influence of PGRs and shelf duration on ascorbic acid (mg 100 mL1) concentrations of 'Kinnow' mandarin
138
4.29 Influence of nutrients on ascorbic acid concentrations (mg 100 mL-1) of juice during seven days shelf life studies
149
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LIST OF SYMBOLS AND ABBREVIATIONS
Abbreviation Description
@ At the rate of o Degree % Percent µg Microgram(s) µL Microliter(s) µM Micromolar µm Micrometer oC Degree Celsius $ United States dollar A Absorbance a* Colour coordinate (a) b* Colour coordinate (b) d Day 2, 4-D 2, 4 dichloro phenoxy acetic acid < Less than > Greater than oF Degree Fahrenheit ± Plus minus AA Ascorbic acid ANOVA Analysis of variance ATP Adenosine tri phosphate C* Chroma C20H14O4 Phenolphthalein C2H2 Ethylene Ca Calcium Ca+ Calcium ion CAN Calcium ammonium nitrate CaCl2 Calcium chloride CO2 Carbon dioxide CP Canopy position CRD Completely Randomized Design CTAB Cetyl Trimethyl Ammonium Bromide CuSO4.5H2O Copper sulphate pent hydrate cv Cultivar(s) dia Diameter DMRT Duncan’s Multiple Range Test DNA Deoxyribonucleic acid DPPH 2, 2-diphenyl-1-picrylhydrazyl EDTA Ethylene diamine tetra acetic acid et al. et alia EU FAO
European Union Food and Agriculture Organization
FC Folin–Ciocalteu FeSO4 Ferrous sulphate FeSO4 7H20 Ferrous sulphate FRAP Ferric-reducing antioxidant power assay
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xiii
FW Fresh weight g Gram (s) GA3 Gibberellic acid GAE Gallic acid equivalents h Hour h° Hue angle H2SO4 Sulfuric acid ha Hectare HCl Hydrochloric acid HClO4 Perchloric acid HNO3 Nitric acid HPLC High performance liquid chromatography HPO3 Phosphoric acid i.e. Illud est IC Inhibition concentration IHS Institute of Horticultural Sciences K Potassium K2SO4 Potassium sulphate Kg Kilogram KNO3 Potassium nitrate kPa Kilo Pascal KPK Khyber Pakhtunkhaw L Liter L-1 Per litre LSD Least significant difference m Meter M Molar mg Mili gram Mg Magnesium mg g-1 Milli gram per gram min Minute MINFA Ministry of Food and Agriculture Mix. Mixture mL Milliliter mM Millimolar mm Millimeter mmol Millimole MMT Million metric ton NS Non-significant Na Sodium NAA Naphthalene acetic acid NaCl Sodium chloride Na2CO3 Sodium carbonateNaHCO3 Sodium bicarbonate NaOH Sodium hydroxide NH4 Ammonium NWFP North West Frontier Province NY New York P Probability PAL Phenylalanine ammonia-lyase
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PBUH Peace be upon Him PG Polygalacturonase PGRs Plant growth regulators pH Hydrogen ion concentration in a solution PME Pectin methyl esterases ppm Parts per million PRTC Postharvest Research and Training Centre Put Putrescine RCBD Randomized complete block design RH Relative Humidity S.E. Standard error SOP Sulphate of potash Spd Spermidine Spm Spermine SSP Single super phosphate TA Total titratable acidity TEAC Trolox equivalent antioxidant capacity TPC Total phenolic contents TSS Total soluble solids UAF University of Agriculture, Faisalabad UK United Kingdom USA United States of America
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ABSTRACT
Rind quality is indispensable for the external appearance and marketability of citrus fruit
especially for fresh consumption. Among many factors affecting citrus rind quality, tree age
is the most important one, but remains unexplored so far. This study was carried out during
2007-11 and comprised of two parts. The first part of study includes the experiments
exploring fruit quality in relation to different tree age, canopy position and fruit size. This
study also revealed the cell number, cell size, endogenous nutrients and fruit pectin
concentrations (rind and rag) in relation to tree age during fruit growth and development. A
comparison of fruit quality of different age groups (3 year, 6 year, 18 year, 35 year) showed
that fruit obtained from young trees (3-year-old) were poor in fruit quality such as having
more rough rind, rind thickness, rind mass (%) and less juice mass (%), TSS and acidity.
Moreover, fruit from young trees had lower rind macro nutrient concentrations (P, Ca) and
higher rind micro-nutrient concentrations (Mn and Fe). Fruit in internal canopy position had
significantly better fruit quality (smooth rind, less rind thickness, more juice contents)
whereas, those in external canopy position were better in biochemical fruit quality such as
(TSS), titratable acidity (TA), sugars and ascorbic acid (AA) concentrations. Large sized fruit
had more rind mass (%), rind thickness, and lower juice mass (%), TSS, TA (%) and TSS:TA
ratio during ambient (20±2°C and 60-65% RH) and cold storage (4±1°C and 75-80% RH)
conditions. From nutritional aspects, during fruit growth and development, fruit from six-
year-old trees were nutrient deficient in rind (N, P and K), rag and leaf (N) concentrations,
while 18-year-old trees were deficient in rag and leaf nutrient (P, K) concentrations. Pectin
analysis showed that fruit from 6-year-old trees were deficient in rind total pectin,
protopectin and rag protopectin concentrations, whereas fruit from 35-year-old trees were
higher in rind water soluble pectin (WSP), total pectin and fruit from 18-year-old trees were
higher in rind total pectin and rind and rag WSP. Anatomical studies of tissues from different
age groups demonstrated increased cell number with lower cell size in rind tissue of 6-year-
old trees in comparison with 18 and 35-year-old trees. Correlation analysis revealed that leaf
N contents correlated positively with cell size in fruit from 18 and 35-year-old trees. Cell size
was negatively correlated with rind P concentrations and positively correlated with leaf P
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concentrations in fruit from all tree age groups. In second part of the study, the potential of
exogenous application of PGRs and nutrients were explored in improving fruit quality of
young 'Kinnow' orchards. The PGRs like gibberellic acid (GA3), 2, 4 dichlorophenoxy acetic
acid (2, 4-D), putrescine (Put) and spermine (Spm) were applied before and after colour
break to young (3-4 years old) 'Kinnow' mandarin trees and their influence on fruit quality
under ambient (20±2°C and 60-65% RH) and cold storage (4±1°C and 75-80% RH)
conditions was determined. Only 2, 4-D significantly improved TA (%) and TSS:TA ratio
during shelflife studies. GA3 and Put treated fruit exhibited maximum mass loss (%) during
shelf studies and cold storage respectively. GA3 10 mg L-1
and cytokinins (kinetin and
benzyladenine) 30 mg L-1
applications at fruit setting stage significantly improved juice (%)
and reduced rag (%). In nutritional experiments, sulphate of potash (SOP), single super
phosphate (SSP), urea, calcium ammonium nitrate (CAN), Wokozim and Isabion were
applied to improve fruit quality. Wokozim application reduced rind thickness and improved
reducing sugars of fruit, SSP improved juice contents, ascorbic acid (AA) and reduced rind
mass (%) although not significant than control; SOP improved AA concentrations in
'Kinnow' mandarin juice and CAN improved TSS and AA concentrations. In conclusion, tree
age exhibited significant influence on 'Kinnow' mandarin fruit quality as fruit from young
trees (3-years-old) showed inferior fruit quality. Moreover, rind of fruit from young trees had
lower macro- (N, P and Ca) and higher micro-nutrient (Mn and Fe) concentrations. In young
trees, macronutrients (P and Ca) and micronutrients (Cu, Mn, Fe and Zn) showed a negative
correlation with fruit rind thickness. Large sized fruit from all tree age groups exhibited poor
quality. Among PGRs, autumn application of 2, 4-D (10 ppm) to young 'Kinnow' mandarin
trees significantly improved TA and TSS:TA ratio. Spring application of cytokinin especially
kinetin, among nutrients SSP and CAN and among growth stimulator Wokozim (PGRs and
nutrient solution) positively affected fruit physical (rind thickness, total seed, juice, rind and
rag mass) and biochemical (TSS, reducing sugars, TA and AA) quality parameters (although
some seasonal variations also exist) thus showing their potential for improving fruit quality
of young 'Kinnow' mandarin orchards. An improvement in fruit quality of young orchards (3-
6 years) can help extend the productive window of 'Kinnow' mandarin orchards.
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3
Chapter-1
GENERAL INTRODUCTION
'Kinnow' is a cross of Citrus nobilis Lour × Citrus deliciosa Tenora, the first generation
hybrid with the King (female) and Willow leaf (male) as parents. It was developed by H.B.
Frost at University of California, during 1925 (Rajput and Haribabu, 1985) and was
introduced from California to Pakistan (Experimental Fruit Garden of Punjab Agricultural
College and Research Institute Lyallpur now Faisalabad) during 1943-44 (Malik, 1992).
'Kinnow' mandarin monopolized the citrus industry of Pakistan due to its good yield and
quality and its better adaptation to the environmental conditions of Punjab (Ahmad et al.,
2006b). Pakistan currently ranks 11th
in mandarin production in international market (FAO,
2009). 'Kinnow' mandarin produces more than 60% in the country's citriculture (Altaf and
Khan, 2009). 'Kinnow' is mainly exported to Russia, Iran and the Gulf States. Pakistan with
an annual export volume of 250,000 tons is the sixth largest mandarin exporter in the world,
however, in terms of value earned, it ranked 11th
due to low unit price (US $ 249 tonne-1
) in
international market (FAO, 2009), owing mainly to poor fruit quality and yield. The external
presentation of fruit is also not according to international standards.
Fruit quality varies with cultural practices, pre and postharvest handling, storage and
distribution system and also with age of the tree. There are reports that citrus fruit from
young vigorously growing trees exhibit low total soluble solids (TSS) and acids and high
TSS to acid ratios (Hearn, 1993). Tree age affects acidity and TSS of 'Satsuma' mandarin
(Matsumato et al., 1972) and juice contents, TSS, acidity and ripeness index of oranges
(Frometa and Echazabal, 1988). Ozeker (2000) reported that 'Marsh' seedless grapefruit
harvested from 20-year-old trees produced bigger fruit with thinner rinds compared with 34-
year-old trees. Postharvest disorders were higher in pome fruit harvested from young trees
(Bramlage, 1993), while quality of apples was inferior from trees of old age (Smith, 2003).
Fruit from younger apple tree showed lowest storage potential with more firm fruit which
quickly lost flavour and quality during shelflife and storage, when compared with fruit from
middle and old aged trees (Tahir et al., 2007). So far, no studies have been published on the
relationship between tree age and fruit quality of 'Kinnow' mandarin.
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4
In Pakistan, the life span of citrus (mainly 'Kinnow' mandarin) tree is declining due to many
biotic and abiotic factors (Ahmad et al., 2006b) and on an average seldom exceeds 25 years
(Ibrahim, 2004). In more than 40 percent cases, tree decline starts at the age of 10 years,
which is the prime age of production (Ahmad et al., 2006b). However, in other countries
economic life of citrus tree is 50-100 years depending on good management practices
(Chaudhary et al., 2004). In Pakistan, citrus tree takes 8-9 years for commercial fruit
production, whereas in other countries like Australia this period is only 6 years (Johnson,
2006). Citrus trees do not produce similar quality fruit throughout the life of an orchard and
need replantation after a certain age due to decline issue. This results in wastage of time and
resources of growers. On the other hand, young 'Kinnow' mandarin trees produce coarse
skinned fruit with less juice contents, and exporters are reluctant to take fruit from young
orchards (Malik, Personal Communication). Moreover, fruit from young trees also contains
less total soluble solids (Hearn, 1993), hence rejected by the processers. Due to these reasons
fruit from young trees are often sold in local market at very low price thus reducing the
income for citrus growers.
Therefore, it is essential to extend the productivity of 'Kinnow' mandarin orchards which is
possible in two ways: 1) manage decline related factors and extend life span beyond 15 years
and (2) improve fruit quality in young orchards, thereby increasing early returns. Lot of
research work has been done with regard to the first possibility by tree health management
(Batool et al., 2007; Chung and Brlansky, 2005), whereas limited information is available for
improving fruit quality of young orchards.
Main obstacle in quality fruit production from young orchards is their excessive vegetative
growth and poor fruit quality. Plant growth regulators (PGR) have been used to manipulate
vegetative and reproductive growth to modify fruit set and fruit growth and to improve fruit
quality (reducing rind thickness, rind contents and improving juice contents) in mature citrus
trees (Fidelibus et al., 2002a; Kaseem et al., 2011; Pozo et al., 2000; Saleem et al., 2008c).
However, to the best of our knowledge their application in young orchards has not been
reported elsewhere.
The role of mineral nutrients in different parts of citrus fruit and their relation with fruit
quality is well documented in literature (Mattos et al., 2003; Paramasivam et al., 2000; Raza
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5
et al., 1999; Xiao et al., 2007). However, no study has been reported to determine the rind
nutrient concentrations from trees of varying age and to establish a correlation between rind
nutrient concentrations and rind quality.
Fruit position in the canopy (Barry et al., 2003; 2004ab; Khan et al., 2009) and fruit size
(Barry et al., 2004a; Ketsa, 1988) has been reported to affect fruit quality. Low temperature
storage and long-distance fruit transport allow an extended market period for more regulated
fruit supply. Currently, no information is available on the effect of tree age, fruit position and
fruit size on 'Kinnow' mandarin fruit quality under ambient (20±2°C) as well as in cold
storage (4±1°C) conditions.
It can be summarized that there is a need for comprehensive research to determine the
possible reasons for variation in fruit quality with tree age and its improvement. This thesis
reports the relationships between tree age, storage potential and fruit quality. The objectives
of this study were:
To explain the physiological basis for poor fruit quality in young orchards.
To develop fruit quality and storage potential profile of fruit from trees of
different age groups.
To explore potential of exogenous application of growth regulators and nutrients
in improving fruit quality of young orchards.
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6
Chapter-2
GENERAL REVIEW OF LITERATURE
2.1 Introduction
The loose skinned oranges are generally known as mandarins. Mandarin and tangerines are
names used more or less interchangeably to designate the whole group. These two groups are
differentiated only on the basis of colour of the fruit; the name tangerine is strictly used for
those varieties which are producing deep orange or scarlet fruits. Niaz (2004) described six
distinct groups of mandarin i.e., King, Satsuma, Mandarin, Tangerine, Mandarin-lime and
Mitis groups. The mandarin is native to south-eastern Asia and the Philippines (Mortan,
1987). The mandarins are also known by their indigenous names in different countries. In
Philippines, all mandarin oranges are called Naranjita and in Spain these are named as
Mandarina.
2.2 Origin and Distribution
The 'Kinnow' is a hybrid of two citrus cultivars 'King' (Citrus nobilis) × 'Willow Leaf' (Citrus
deliciosa) developed by H.B. Frost at the Citrus Research Centre of the University of
California, Riverside, USA in 1925 and after evaluation it was named and released as a new
variety for commercial cultivation in 1935 (Rajput and Haribabu, 1985). In 1940, 'Kinnow'
was introduced to Punjab Agriculture College and Research Institute, Faisalabad (former
Lyallpur), Pakistan (Malik, 1992). In India, J.C. Bakhshi introduced this variety to the Punjab
Agricultural University, Regional Fruit Research Station, Abohar in 1954 (Wikipedia
contributors, 2012). 'Kinnow' has been distributed widely and is being grown commercially
in Punjab province of both Pakistan and India and to some extent in California and Arizona
(Reuther et al., 1967). Its tree has vigorous and upright growth habit, with great heat
tolerance, cold-resistance and having a strong tendency of alternate bearing with large crop
of smaller fruit followed by very small crop of larger fruit (Reuther et al., 1967). The fruit is
medium sized, slightly oblate with a smooth orange rind that does not peel especially well for
a mandarin. Fruit contains 9 to 10 segments, firm, separating fairly easily with axis solid to
semi-hollow. The flesh is yellowish-orange, seedy, and very juicy having a rich distinctive
flavour. 'Kinnow' is mid-season in maturity and holds well on the tree (Reuther et al., 1967).
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7
'Kinnow' female parent King (Citrus nobilis) is now known as a natural tangor, hybrid of
mandarin (Citrus reticulata) and orange (Citrus sinensis). The most important mandarin in
subcontinent is the Santra (Niaz et al., 2004) or Sangtara which also been found in the region
of Lahore, Pakistan during 15th
century (Sabir, 2012). Further, sangtara has been mentioned
in the famous book ‘Ain-e-Akbari’ by Mughal Emperor, Akbar Khan. After this the fruit was
popularly called as ‘Shahi Sangtara’ or King Orange. Mughal Emperor, Humayun Khan
praised this fruit in the following words. “Indeed there is no tasty fruit than the sangtareh”
(Sabir, 2012). In 1880 six fruit of the 'King' mandarin were sent by John A. Bingham, a
United States Minister to Japan from South Vietnam (Saigon) to Dr. H.S. Magee at
Riverside, California. The latter he sent two seedlings to J.C. Stovin of Winter Park, Florida
in 1882 (Mortan, 1987). The most distinctive feature of King mandarin is its very high heat
requirement for the attainment of horticultural maturity and good quality, for which reason it
is the late ripening variety of the mandarins (Reuther et al., 1967).
The parentage and mode of origin of second parent (Willow leaf) of 'Kinnow' are not known
but it seems likely that it arose as a chance seedling from a mandarin variety or form of
Chinese origin. After careful review of the literature, Chapot (1962) concluded that it
appeared in Italy between 1810 and 1818. It was brought to the United States by the Italian
ambassador at New Orleans and planted in the consulate grounds there sometime between
1840 and 1850, apparently being the first mandarin to reach this country. Not long thereafter,
it was taken to Florida and thence probably to California and elsewhere (Reuther et al.,
1967).
The other related hybrids of the same parentage (King × Willow leaf) are 'Encore', 'Honey'
(not the Murcott of Florida) and 'Wilking' (Reuther et al., 1967).
2.3 Citrus Industry of the World
Citrus is the most widely produced fruit of the world and is grown in more than 80 countries
(Chang, 1992).
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8
2.3.1 World Mandarin and Tangerine Production
Pakistan is on eighth position in terms of mandarin quantity produced and production value
(FAO, 2010). Approximately 95% world 'Kinnow' is produced in Pakistan.
Source: FAO (2010)
Fig.2.1 World mandarin and tangerine production
2.3.2 World Mandarin and Tangerine Export
In international mandarin and tangerine trade, Pakistan ranks sixth in terms of quantity
exported and on eleventh in terms of value earned from export (FAO, 2009).
Source: FAO (2009)
Fig.2.2 World mandarin and tangerine export
2500109
421962
277339
212117
196843
194159
151886
141489
133335
116800
Production ($1000) China
Spain
Brazil
Turkey
Egypt
Japan
Republic of Korea
Pakistan
USA
Morocco
10121000
1708200
1122730
858699
786000
614871
572780 572780
539770
472834
Production (MT)
China
Spain
Brazil
Turkey
Egypt
Japan
Republic of Korea
Pakistan
USA
Morocco
52%
13%
9%
8%
6% 4%
3% 2% 2% 1%
Value (1000 $)
Spain
China
EU(27)ex.int
Turkey
Morocco
Netherlands
Argentina
Italy
South Africa
Pakistan
39%
21% 10%
7%
7%
5% 3%
3% 3%
2%
Quantity (tonnes)
Spain
China
Turkey
Morocco
EU(27)ex.int
Pakistan
South Africa
Argentina
Netherlands
Italy
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9
2.4 Citrus Industry of Pakistan
In Pakistan, citrus ('Kinnow') is the top ranking fruit crop in terms of area and production
followed by mango, apple and guava (Anonymous, 2009). About 95% of citrus area is
located in Punjab (Anonymous, 2009), especially Sargodha district.
Source: Anonymous (2009)
Fig 2.3 Citrus area and production in Pakistan
2.4.1 Mandarin export from Pakistan
Currently 'Kinnow' is being exported to different countries of the world, major markets
include Russia, Afghanistan, Iran, UAE and Saudi Arabia etc (Anonymous, 2009).
Table 2.1 Mandarin export from Pakistan during 2008-09
Countries Quantity (Tonnes) Value (1000 US $) Unit price ($ tonne-1
)
Russian Federation 36263.68 9186.44 253.32
Afghanistan 34127.21 11939.68 349.86
Iran 33493.78 6869.34 205.09
UAE 25722.1 4145.81 161.18
Saudi Arabia 10934.28 1944.44 177.83
Ukraine 8103.54 1809.60 223.31
Kuwait 5763.24 842.60 146.20
199940
170166 36056
113029
15358 62238
Area (Hectare)
Citrus
Mango
Banana
Apple
Grapes
Guava
2132276
1727932
157319
441062
76095
512295
Production (Tonnes)
Citrus
Mango
Banana
Apple
Grapes
Guava
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10
2.5 Citrus Fruit Anatomy
Citrus fruit are classified as ‘hesperidum’ a special type of berry which develops through
growth and development of a single ovary consisting of 8-16 carpels clustered around and
joined at the floral axis and surrounded by tough leathery rind (Schneider, 1968). The
endocarp (edible portion) of the fruit comprised of segments (carpels) in which juice vesicles
and seeds grow. The rind is divided into exocarp or flavedo (outer coloured part) and
mesocarp or albedo (inner white part) (Ladaniya, 2008). The flavedo comprises of the
epicarp, covered by a protective skin or cuticle, the hypodermis, the outer mesocarp and oil
glands.
Fig. 2.4 Transverse section of citrus fruit (Ladaniya, 2008)
2.6 Fruit Growth and Development
Iglesias et al. (2007) described the three stages of citrus fruit growth and development
including cell division, cell elongation and maturation. The lengths of these stages vary
depending on citrus variety and location. The length of cell division (stage-I) is from 4 to 9
weeks. Lowell et al. (1989) reported that during stage of cell division pericarp (rind) grows
very quickly.
During stage-II, fruit growth and development is mainly due to cell enlargement and
differentiation. In this stage cell division only persists in flavedo and the tips of the juice
sacs. It has been reported that during the stage-II, rind thickness, reduced while pulp volume
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11
increased continuously due to water accumulation and cell enlargement (Iglesias et al.,
2007).
During the third stage (i.e. maturation) the rate of growth is much lower than in stage II. Fruit
ripening starts during this stage with disappearance of chlorophyll pigments and subsequent
development of carotenoids pigments.
2.7 Fruit Quality
Quality is very important for consumption and marketability of produce and it varies from
person to person. In citrus external fruit quality parameters include colour, size, rind
smoothness and blemishes whereas internal fruit quality includes rind thickness, juice
concentrations, ascorbic acid, acidity, TSS, TSS:TA.
2.7.1 Factors affecting fruit quality
In the past, studies have been conducted to investigate the factors affecting fruit quality in
various fruit crops. Selected research work is being summarized under different factors with
regards to their effect on physical and biochemical fruit quality as under:
2.7.1.1 Tree age
Tree age has a pronounced effect on fruit physical and biochemical quality parameters.
2.7.1.1.1 Physical fruit quality
Young trees tend to be more vigorous than old mature trees. Due to vigorous growth young
trees have poor rind colour development compared with older less vigorous trees (Krajewski,
1997). Fruit from mature 'Navel' orange trees had severe outbreaks of the rind disorder
albedo breakdown (crease) as compared to fruit from young trees (Storey and Treeby, 2002).
Fruit obtained from 5-10 year old Prunus salicina, trees yielded heavier fruits with larger
transversal diameter as compared to fruit obtained from 20-30 years old trees (DongHui et
al., 2005).
Ozeker (2000) reported that 'Marsh seedless' grapefruit harvested from younger trees (20
years old) were bigger and heavier in size with thinner rind than old trees (34 years old). Age
of the tree and cultivar influence the juice concentrations of oranges (Frometa and Echazabal,
1988). In avocado, grey pulp problem was found higher in young as compared to old trees
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12
(Snijder et al., 2002).
2.7.1.1.2 Biochemical fruit quality
In Prunus salicina, 5-10 year old trees had higher ascorbic acid concentrations than 20-30
year old trees however taste, acidity and soluble solid contents did not significantly vary with
the tree age (DongHui et al., 2005). Tree age also affected storability of fruit as Tahir et al.
(2007) reported that apple fruit from young trees (younger than 6 years) had a lower
resistance to bruising and Pezicula malicorticis decay, while fruit from trees older than 20
years were prone to reduced quality and storability. Asrey et al. (2007) reported that fruit
from upper canopy of 15 year old guava trees had higher TSS (11.85%), total sugars (7.50%)
and lowest acidity (0.28%).
2.7.1.2 Fruit size
Fruit size is one of the key quality factors in the fruit trade. Increased fruit size is desirable
for mandarin-type fruits as small size fruit fetchs low prices on the fresh market thereby
causing considerable economic losses (Guardiola et al., 1988). Ghaffar (1991) studied that
size of the fruit is very important in quality evaluation, particularly when fruit of most
cultivars are immature and or too small. It is also sometimes used as a criterion for spot
picking.
2.7.1.2.1 Physical fruit quality
Fruit size influences skin colour in peaches. In small sized fruit of peach cv 'Hashiba-
hakuho,' skin colour on the cheeks (yellow) was dark and in large sized fruit the colour at the
top (reddish) was dull and dark yellowish in Shimizu-'Hakuto' and 'Hakurei' respectively,
compared to fruit of other sizes (Okamoto et al., 2003). Mass loss and fruit firmness during
storage is very important and influenced by fruit size. As smaller banana fruit showed
significantly higher mass loss and lower fruit firmness when compared with larger banana
fruit (Ahmad et al., 2006a). However smaller 'Kinnow' (Malik et al., 2007) and apple (De
Salvador et al., 2006) fruit were firmer than medium and large sized fruit. In smaller
grapefruit, mass loss percentage was significantly higher than that of larger fruit (Paily et al.,
2004). Small sized Kiwifruit (Actinidia chinensis) of 'Hort 16A' lose firmness earlier than
medium and large fruit however, small AU Golden Sunshine fruit had greater firmness in the
later weeks of cold storage when compared with medium and large fruit (Spiers et al., 2011).
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13
Juice (%) also varies with fruit size. Paily et al. (2004) reported that percentage of fruit juice
in grapefruit with large diameter was always higher than in small diameter fruit. Sandhu
(1992) reported that 'Kinnow' mandarin fruit from extra-large fruit size had lower juice (%).
2.7.1.2.2 Biochemical fruit quality
Fruit size had a marked influence on biochemical fruit quality in many fruits. Large sized
grape barries have less sugar concentrations and inadequate aroma (Hirano et al., 1996).
Large sized peaches, which were produced on heavily fertilized trees, have very poor flavour
and aroma than in trees fertilized normally (Jia et al., 1999). In small and medium sized
peach of cultivars 'Hakuho', 'Shimizu-hakuto' and 'Hakurei' sucrose and fructose
concentrations were higher while, malic and citric acid concentrations were more in large
sized fruits of those cultivars (Okamoto et al., 2003). Small citrus fruit had higher TSS than
large sized fruits (Hardy and Sanderson, 2010). Ketsa (1988) described that ascorbic acid
was not related to fruit size in tangerine. TSS and acidity decreased with increasing fruit size
in tangerine (Ketsa, 1988), 'Satsuma' mandarin (Kihare et al., 1982) and 'Kinnow' mandarin
(Malik et al., 2007). Smaller bananas showed significantly higher TSS when compared with
larger bananas (Ahmad et al., 2006a). Sandhu (1992) reported that 'Kinnow' mandarin fruit
from extra-large fruit size had lower Brix and acidity as compared to other fruit sizes
however ascorbic acid concentrations did not vary with fruit size. Miller (1990) reported a
negative correlation between fruit size and Brix of 'Valencia' orange. In small sized Kiwifruit
(Actinidia chinensis) of 'Hort 16A' variety TSS:TA, internal colour and % dry matter were
not affected by fruit size contrarily, small 'AU Golden Sunshine' fruit had lower TSS, less
internal colour development, and greater firmness in the later weeks of cold storage when
compared with medium and large fruit (Spiers et al., 2011). However, some studies reported
that fruit size had no significant effect on biochemical fruit quality of tangerine
(Jungsakulrujirek and Noomhorm, 1998) after harvest and grapefruit (Paily et al., 2004)
during storage.
As evident from above literature review fruit quality varies with tree age and fruit size.
However, their combined effect on fruit quality has not been reported in literature to the best
of our knowledge and yet to be explored.
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14
2.7.1.3 Canopy position
Large fruit size, thin rind, high total soluble solids and solids to acid ratios are desirable
quality attributes in citrus fruit which are dependent upon interception of light within the
canopy. Considerable review on influence of canopy position on fruit physical and
biochemical characteristics is presented as under:
2.7.1.3.1 Physical fruit quality
Fruit canopy position influences fruit quality probably due to light penetration. Orlando
tangelo fruit from bottom and middle canopy positions were firmer, juicy and had greatest
Hue (H) value when compared with fruit from top-canopy position (Morales et al., 2000).
Inner canopy fruit during the immature stage (January-March/April) had less green colour
(lower hue angle) compared to outer canopy fruit but after colour break (between March and
April) the outside fruit developed more orange colour (lower hue angle) in contrast with
inside fruit moreover, fruit from inner canopy position were lighter and smaller (diameter and
length) compared to outer canopy fruit (Cronje et al., 2011). Khan et al. (2009) reported that
'Kinnow' fruit from inside canopy were heavier (20%) and larger in volume (22.3%), had
more rind and rag mass and less juice (%) as compared with fruit harvested from top of the
tree canopy, however canopy position had no significant effect on rind thickness of fruit.
Jawanda et al. (1973) also reported that fruit from the inner part of the canopy were heavier
with less juice and more rind percentage than from other sides of tree canopy. Higher fruit
mass, rind thickness, rind fresh and dry mass, was found in 'Kinnow' mandarin, 'Red Blush'
grape fruit 'Valencia' orange and 'Lisbon' lemon form internal canopies than from external
canopies (Fallahi and Moon Jr., 1989). Grapefruit harvested from the shaded positions were
lighter with less juice content than fruit from sun exposed canopy positions (Syvertsen and
Albrigo, 1980b). Lewallen and Marini (2003) reported that peach fruit from the exterior
canopy were larger, had more darker and redder surface than fruit harvested from interior
canopy positions.
2.7.1.3.2 Biochemical fruit quality
Fruit orientation in the canopy has been reported to have strong influence on biochemical
fruit quality. Fruit located in the top-canopy position of 'Orlando' tangelo had highest TSS
and TSS:TA ratio while, TA contents had little variations due to canopy position (Morales et
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15
al., 2000). Similarly Barry et al. (2003) also reported that canopy position had significant
effect on TSS contents and non significant effect on TA of 'Valencia' orange fruit. Jawanda et
al. (1973) reported that acidity and TSS were higher in the upper sides of citrus trees. Orange
fruit harvested from upper canopy positions had high contents of reducing sugars (Uchida et
al., 1985), whilst no effect of fruit position in the canopy was observed on total sugar content
in 'Satsuma' mandarin (Datio and Tominaga, 1981). Khan et al. (2009) reported that 'Kinnow'
mandarin fruit harvested from top of the tree and from outer periphery had significantly
higher in SSC and SSC:TA ratio compared to fruit harvested from inside and lower side of
the tree canopy. In the outside canopy positions of 'Ruby' grapefruit, SSC were higher and
acidity was lower in other canopy positions (Syvertsen and Albrigo, 1980b). In the litchi
fruit, lower brix:acid ratio was observed in lower canopy position than from fruit harvested at
higher canopy positions (Tyas et al., 1998). Asery et al., (2007) found that middle canopy
fruit from 15-year-old trees had higher AA concentrations and lower acidity contents. They
also reported that upper canopy fruit obtained from 15-year-old trees had higher total sugar
contents.
Sectorial position of fruit in the canopy also influences biochemical fruit quality. Citrus fruit
harvested from the southern top canopy position had higher TSS and juice contents than fruit
from other canopy positions (Izumi et al., 1990). 'Tarocco' orange harvested from the
external southern side of the tree had higher TSS and lower acid levels, resulting in higher
TSS:acid ratio and improved taste (Agabbio et al., 1999). 'Torocco' orange fruit from the
external southern side of the tree had higher SSC and lower acid contents in comparison to
fruit from interior and northern parts of the tree canopy (Agabbio et al., 1999). In grapefruit,
southern top canopy positions had fruit with more TSS contents and less TA and higher
TSS:TA ratios due to highest temperature and lowest water potential (Syvertsen and Albrigo,
1980b).
Above literature review exhibited that fruit position in a canopy had significant influence on
fruit quality. Tree canopy increases with increase in tree age so is the difference in fruit
quality. No research work has been reported on the combined effect of tree age and fruit
canopy position on fruit quality in Citrus especially in cv 'Kinnow' mandarin.
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16
2.7.1.4 Plant growth regulators
Endogenous PGR production is dependent upon phenological stages of the plant and their
concentration and types vary during fruit growth and development (Guardiola et al., 1993;
Kakkar and Rai, 1993; Malik and Singh, 2004). Auxins, GA3 and cytokonin concentrations
were higher in young citrus fruitlets, whereas the concentration of growth inhibitors like
abscisic acids was higher during fruit maturation and senescence (Bain, 1958). In mandarin,
polyamine levels changed with fruit growth curve and its higher amounts were found during
cell division stage (Nathan et al., 1984). Putrescine (Put) concentration in rind and rag of
'Navel' oranges was found higher during ripening (Tassoni et al., 2004). In young orange
fruit, activity of GA3 was relatively high whereas auxin was detected in small amounts
(Goren and Goldschmidt, 1970). In Citrus unshu, endogenous levels of benzyladenine (BA)
and GA3 fell to a much lower value with in few days after flower opening, and it coincided
with a marked reduction in the fruit response to these hormones (Guardiola et al., 1993). In
citrus, cytokinins levels were found higher in developing ovaries at anthesis and were
involved in cell division whereas auxin was found higher during cell enlargement phase and
played important role in maintenance of cell size (Iglesias et al., 2007).
Endogenous PGRs concentrations vary with age of the plant and type of plant part. Juvenile
'Pickstone Valencia' orange plants had higher cytokinin concentrations in fibrous root tips
than adult plants, however during bud growth all cytokinin levels decreased in juvenile buds,
whereas in adult plants polar cytokinin decreased slightly but non polar increased (Hendry et
al., 1982). In peach (Prunus persica) trees total polyamine concentrations increased with
increasing tree age whereas in pine (Pinus radiata) trees total polyamine concentrations
decreased with tree age (Fraga et al., 2004). Putrescine (Put) was found higher in juvenile
tissues of hazel nut (Corylus avellana L.) (Rey et al., 1994) while, opposite was reported in
grapevine (Vitis vinifera L. cv. Pinot noir) (Heloir et al., 1989). Paschalidis and Roubelakis-
Angelakis (2005) reported that in youngest tissues and shoot apex of tobacco plant
spermidine (Spd) and spermine (Spm) concentrations were found higher. Fernandez (2003)
reported that endogenous Gibberellic acid types vary with age of the Pinus radiate, trees with
juvenile plants having higher GA7 and GA9 and lower GA4 as compared to mature trees,
whereas GA3 and GA20 did not vary with tree age. Similarly Davenport et al. (2000) reported
that endogenous GA3 levels did not vary with age of mango stem whereas other GA types
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17
declined with stem maturity. Husen and Pal (2006) reported that endogenous auxin
concentrations decreased with age of the donor plant as cutting from mature plants required
higher amount of exogenous auxins for rooting. Endogenous PGRs varies with tree age and
fruit development stages and their exogenous application at different growth and
developmental stages is well documented in mature citrus trees (Fidelibus et al., 2002a).
However, their application in young 'Kinnow' mandarin orchards have not been reported and
yet to be explored.
Plant growth regulators (PGRs) have been used to improve citrus fruit quality, mainly
affecting on fruit size and peel properties. PGRs are routinely used by many citrus growers in
Spain, California, Australia, South Africa and Israel to increase crop productivity. PGRs may
be used to improve fruit set, increase fruit size, improve on tree storage and reduce hand-
suckering by controlling trunk sprout growth in young trees. Several studies have shown that
PGRs play an important role in manipulating vegetative and reproductive growth and
improving fruit quality (Malik and Singh, 2004; Saleem et al., 2008c; Saleem et al., 2008a).
2.7.1.4.1 Physical fruit quality
Cytokinins are substituted adenine compounds, naturally occurring in plants, which promote
cell division in tissue systems (Salisbury and Ross, 1991). Cytokinins are responsible for
delaying fruit colour development in citrus. Benzyladenine (BA) significantly delayed
chlorophyll degradation in 'Feizixiao' mandarin and inhibited anthocyonin biosynthesis
(Wang et al., 2005). BA delays fruit abscission and increases the amount of re-greening in
'Valencia' oranges (Cooper and Henry, 1968). Eilati et al. (1969) reported that BA did not
influence the carotenoid accumulation during the onset of fruit maturation. In contrast
Gracia-Luis et al. (1986) demonstrated that cytokinin reduced the carotenoid accumulation in
citrus rind and could be used as maturation retardant. The Kinetin and Benzyl adenine
treatments in 8 year-old 'Kinnow' mandarin tree reduced chlorophyll degradation (Nagar,
1993).
Cytokinin efficacy depends upon its stage of application. BA when applied to adult (20 year-
old) Citrus unshiu at flower opening stage increased ovary growth but the sensitivity of the
fruitlet to growth regulator decreased with age of fruitlet and no growth increment was
observed when BA was applied 11 days after anthesis moreover BA application increased
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18
cell division in pericarp (rind) of the fruit resulting in more rind thickness (Guardiola et al.,
1993). Cytokinins are being used in citrus fruits to improve their fruit quality. However, their
applications to improve fruit quality in young citrus tree is lacking and yet to be explored.
Effectiveness of Gibberellic acid (GA3) varies with its application time in different cultivars
of citrus. Foliar application of GA3 during colour break delayed fruit ageing in cultivar
'Satsuma' mandarin (Kuraoka et al., 1977) and 'Navel' orange (Riehl et al., 1996). Ladaniya
(1997) applied GA3 to 'Nagpur' mandarin at colour break and reported that GA3 improved
fruit firmness, delayed colour development and reduced fruit mass loss during storage. Davis
et al. (1999) determined the optimal time for GA3 application in 14-year-old 'Hamlin' sweet
orange and reported that fruit treated with GA3 at colour break had statistically greater juice
yield than fruit from non sprayed trees. Fidelibus et al. (2002b) reported that application of
GA3 at about colour break increased juice weight of sweet orange, reduced rind thickness and
markedly improved the strength of the rind in shear and tension. Fidelibus et al. (2002a)
applied GA3 on mature ‘Hamlin', 'Pineapple', and 'Valencia' sweet oranges from September to
December and reported that earliest applications were most effective in maintaining rind
puncture resistance compared with control fruit, while the later application dates resulted in
the most green peel colour at harvest. Pre-harvest treatment with GA3 application delayed
rind color development of on-tree-stored citrus fruit (Ferguson et al., 1982). Gracia-Luis et
al. (1992) reported that late application of GA3 had no effect on fruit growth and quality, but
early GA3 applications reduced rind thickness at maturation.
In 'Ponkan' mandarin, GA3 application at 200 ppm one month after anthesis reduced fruit size
(Moreira et al., 1996) while, its application to young fruitlets significantly increased fruit size
in grapefruit (Berhow, 2000) and fruit mass and diameter in 'Balady' mandarin (El-Hammady
et al., 2000). In citrus, GA3 applications retard rind colour development and rind aging. GA3
application before and after harvest significantly slowed the rate of rind colour change and
the rate of rind softening of 'Clementine ' mandarin (El-Otmani et al., 1990) and reduced the
incidence of rind disorders in 'Ponkan' mandarin (Tominaga et al., 1998) and 'Balady'
mandarin (El-Hammady et al., 2000). No effect of GA3 was found on final fruit size of
'Satsuma' mandarin (Guardiola et al., 1993), fruit weight of 'Navel' orange (Schafer et al.,
2000) and on length, diameter and fresh fruit mass of 'Pera' orange (Almeida et al., 2004).
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Delayed softening by GA3 has been shown for on-tree-stored navel orange (Coggins, 1969)
and grapefruit (Ferguson et al., 1982). GA3 applications at various time during fruit growth
and development is widely reported in literature. However, its application at various time in
young citrus tree is not reported and yet to be studied.
Among auxins, 2, 4-D is widely used in mature citrus trees as it has an injurious effect on
young trees. Delayed rind colour development of on-tree-stored grapefruit by pre-harvest
treatment with 2, 4-D was reported by Ferguson et al., (1982). Delayed softening by 2, 4-D
has been shown for on-tree-stored 'Navel' orange (Coggins, 1969) and for cold-stored
grapefruit (Ferguson et al., 1982). Application of 2,4-D delayed ripening and colour
development (Lodh et al., 1963) and retained greenness of buttons (Sonkar et al., 1999) in
mandarins. The styles persisted on treated fruit until late into fruit development (Krezdom,
1969; Verreynne and Mupambi, 2010). Stewart and Klotz (1947) reported that the
application of 225 mg L-1
2,4-D on 'Valencia' and 'Washington Navel' oranges resulted in a
coarse rind due to enlarged oil glands. The fruit were also cylindrical in shape and the
'Valencia' oranges developed a small secondary fruit. Similar effects were noted on grapefruit
(Stewart and Parker, 1947). When applied as a fruit growth enhancer, 2,4-D treated fruit were
greener and more elongated compared to the control fruit (Stewart et al., 1951). It increased
the percentage of the rind as well as the rag and reduced the juice content of the treated fruit
(Stewart and Parker, 1947).
Some reports are also found whereby 2,4-D reduced juice percentage but had no effect on
rind thickness (Saavedra 2006; Verreynne and Mupambi, 2008). In 'Washington Navel'
orange there was the development of small rudimentary seeds in treated fruit (Stewart and
Klotz, 1947). When applied at full bloom to act as a growth enhancer, 2, 4-D also increased
the percentage of the rind as well as the rag and reduced the juice percentage in 'Washington
Navel' fruit (Stewart et al., 1951). Above review revealed that 2, 4-D applications are also
well documented in mature citrus trees. As in young citrus trees vigorous growth is
responsible for poor fruit quality, so the potential of 2, 4-D to suppress vigorous growth and
improve fruit quality is likely to be explored.
Polyamines (PAs) are polycationic compounds of low molecular weight that are present in all
of living organisms and are implicated in various biological processes including plant
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20
growth, development, flowering, fruit ripening senescence and stress response (Malik and
Singh, 2004). PAs include putrescine (Put), spermidine (Spd) and spermine (Spm).
In 15 year old peach trees, preharvest PAs treatment increased fruit firmness during ripening
period (Bregoli et al., 2002). Another effect of PAs infiltration is to ameliorate chlorophyll
breakdown in several plant organs, including fruit, such as in lemon and apricot, since Put
treatment delayed the colour change during storage, which is the indicator of reduced
senescence rate (Valero et al., 1998). Exogenous application of PAs retarded chlorophyll loss
in muskmelon by reducing the hydrolytic activities acting on chloroplast thylakoid
membrane (Lester, 2000). Zheng and Zhang, (2004) reported that Spm significantly reduced
weight loss (%) and fruit decay in 'Ponkan' mandarin after three months storage period.
Exogenous PAs applications improved rind colour and rind smoothness of fruit harvested
from 12-15 year-old sweet orange trees (Saleem et al., 2008a). Author further stated that PAs
(Spd) treatment reduced rind (%), and improved juice (%) and rag (%) in sweet orange fruit.
Little information is available on preharvest PAs application on fruit quality in citrus.
2.7.1.4.2 Biochemical fruit quality
Preharvest applications of Cytokinins significantly influenced biochemical fruit quality in
apple. As Koukourikou-petridou et al. (2007) reported that kinetin when applied at petal fall
stage increased total sugars and TSS of 'Red Chief Delicious' apple. Similarly Al-Absi (2009)
found that BA at 200 ppm applied to apple at fruitlet diameter of about 10 mm significantly
increased TSS contents in comparison with control.
Pre-harvest sprays of GA3 increased juice brix (a measure of TSS) of grapefruit at harvest
(El-Zeftawi, 1980). In citrus, GA3 efficacy varies from cultivar to cultivar. Pre-harvest
application of GA3 had no effect on acid and soluble solids content of 'Navel' orange at
harvest (Coggins, 1969), but when applied to cultivar 'Valencia' orange, it increased solids
and acid in juice (Embleton et al., 1973). On cultivar 'Satsuma' mandarin, GA3 had no effect
on juice soluble solids and acids, but depressed peel sugar content (Kuraoka et al., 1977).
GA3 application to 'Clementine' mandarin increased maturity index during off year while on
year it increased TA and ascorbic acid concentrations of fruits juice (El-Otmani, 2004). GA3
applications also influence fruit quality during storage. Mature green fruit of the 'Mahaley'
orange when treated with GA3 gave superior fruit quality throughout the storage period at 4
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21
or 7oC when compared to control (Al-Doori et al., 1990). Pre-harvest GA3 applications
significantly reduced fruit decay during storage (Coggins, 1969).
Variable effects of growth regulators on citrus fruit quality were reported in the literature.
TSS was reduced while titratable acid content was improved in juice when 'Washington
Navel' fruit was treated with 2, 4-D (Stewart et al., 1951). Pre-harvest sprays of 2, 4-D
increased juice °Brix (a measure of TSS) of grapefruit at harvest (El-Zeftawi, 1980). There
was also a slight decrease in titratable acids and an increase in the soluble solids to acid ratio
of 'Washington Navel' orange by the application of 2, 4-D (Stewart and Klotz, 1947). 2, 4-D
treatment lowered the ABA concentration and prolonged the storage life of 'Valencia'
oranges (Liu and Xu, 1998).
Polyamines application significantly improved sugar and acid contents of various fruits.
Zheng and Zhang (2004) applied PAs to 'Ponkan' mandarin and reported that all PAs
treatments increased TSS contents in comparison with control but the results were not
statistically significant. Exogenous applications of Put (5x10-5
M) increased TSS contents of
apple (Costa and Bagni, 1983). In litchi, Put applications decreased TSS and TSS:TA ratio
(Mitra and Sanyal, 1990). Purwoko et al., (1998) found no significant effect of PAs on TSS
and acidity contents of mango, whereas in papya, spermine reduced TSS contents. Bregoli et
al. (2002) treated peach trees with various levels of PAs, 19 days before harvest and reported
that Spd application significantly reduced TSS of fruit. In 12-15-years-old sweet orange trees
PAs application improved TSS, total and non reducing sugars (Saleem et al., 2008a).
Above review of literature revealed that PGRs (cytokinins, GA3, 2,4-D, and polyamines) are
widely tested in mature fruit trees however, studies on their application in young 'Kinnow'
mandarin tree is lacking and yet to be explored.
2.7.1.5 Mineral nutrition
Endogenous nutritional status of citrus tree influences citrus fruit yield and fruit quality
(Moss, 1972; Storey and Treeby, 2000). Rind phosphorous and rag potassium concentrations
continuously increased as long as 'Kinnow' fruit stayed on the tree (Raza et al., 1999).
Contrarily, Storey and Treeby (2000) reported that in whole fruit of 'Navel' orange P and K
decreased during fruit growth and development, while Ca increased during stage-I and then
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22
decreased during stage-II and stage-III. Sheng et al. (2009) determined nutrient
concentrations in leaf, rind and rag of 'Newhall' and 'Skagg's Bonanza' navel oranges and
reported that nutrient status in each tissue varied differently during fruit growth and
development. Concentration of macronutrients decreased during fruit enlargement, while
micronutrient concentrations first increased and then decreased in four orange varieties
viz.'Valencia', 'Parson Brown', 'Hamlin' and 'Sunbrust' during fruit growth and development
(Paramasivam et al. 2000).
Tree age also effects endogenous nutrient status in fruit. Fruit from mature 'Navel' orange
trees, with a history of frequent and severe outbreaks of the rind disorder albedo breakdown
(crease) had higher albedo K/Ca and Mg/Ca ratios during stage-I (cell division stage) of fruit
development, compared to fruit from young trees (Storey and Treeby, 2002). In the fruit
from the older avocado trees N concentrations were lower, while calcium concentrations
were higher (Snijder et al., 2002).
Endogenous nutrients status of fruit fluctuates with the position of fruit in canopy. In outer
tree canopy fruit flavedo of 'Nules Clementine' mandarin accumulated higher concentrations
of Ca and Mg while, fruit obtained from inner tree canopy accumulated higher levels of K
(Cronje et al., 2011). Asrey et al., (2007) reported that fruit Fe concentrations were higher in
young guava trees. They also found that middle canopy fruit from 15-year-old trees were
richer in Cu and Mn concentrations while magnesium (Mg) was found higher in fruit of 20-
year-old trees. Light exposed kiwifruit (Actinidia deliciosa) had more Ca accumulation as
compared to shaded fruit (Montanare et al., 2006).
Endogenous nutrient status in relation to tree age, canopy position and during fruit
development is well documented in literature. However, exploration of endogenous nutrient
concentrations in relation to tree age and canopy position is not reported in Kinnow mandarin
trees. Moreover endogenous nutrient status in Kinnow mandarin tree during fruit growth and
development is not reported from trees of various age groups.
Alkaline pH and calcareous nature of soil in citrus growing areas resulted in nutrient
deficiencies (Yasin and Manzoor, 2010) and poor fruit quality. Exogenous application of
macro and micronutrients are well documented in literature in improving fruit quality. Some
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23
research work on effect of macro and micronutrients on citrus fruit quality is summarized as
under:
2.7.1.5.1Physical fruit quality
Nitrogen is a pre-requisite nutrient for citrus growth, yield and fruit quality (Alva et al., 2003;
Thompson et al., 2002). Nitrogen plays an important role in various plant biological
processes such as cell division, growth, photosynthesis and respiration (Abbas and Fares,
2008). Saleem et al. (2008b) reported that winter application of low-biuret urea (LBU)
reduced fruit weight and fruit diameter of sweet orange cv. 'Blood Red'. El-Otmani (2004)
reported that urea application to 'Clementine' mandarin increased juice (%) during on-year
while, off-year it had no effect on any fruit quality parameters. Khan (2009) reported that
low-biuret urea application increased juice and rag contents of 'Kinnow' mandarin fruits.
Koseoglu (1995) found a positive correlation between N and rind thickness and Koo (1988)
reported that increasing N rates decreased rind thickness in citrus fruit however, Alva et al.
(2006) found non significant effect of N application on rind thickness of 'Hamlin' orange.
Dou et al. (2005) applied phosphorous at 0, 48 and 96 kg ha-1
to 'Flame' grapefruit trees and
reported that optimum P increased rind colour development, β-carotene and lycopene
contents. Phosphorus deficiency results in a thick rind with a hollow core particularly in
sweet oranges (Ladaniya, 2008).
Potassium plays numerous important functions in plant such as cell division, growth, and
sugar starch metabolism, protein synthesis, enzyme activation, stomatal functions,
photosynthesis, pH stabilization, plant water relations, and transport of metabolites (Abbas
and Fares, 2008). Ashraf et al. (2010) applied K2O (0, 50, 75, 100 kg ha-1
) in the form of
sulphate of potash along with P and N to K deficient orchards in four district of Punjab
(Jhang, Sargodha, T.T. Singh and Faisalabad) and reported that K increased fruit size and
weight of sweet oranges. Ashkevari et al. (2010) reported that K application increased fruit
yield, fruit diameter and fruit length in citrus. Fruit firmness was improved by K in 'Fortune'
mandarin (El-Hilali et al., 2004). Foliar application of KNO3 increased fruit size in 'Valencia'
orange (Du Plessis and Koen, 1988). Erner (1993) found that KNO3 applications increased
fruit size of 'Valencia' orange and grapefruit. K increased fruit size and yield Ritenour et al.
(2002), but excessive K results in large and coarse fruit with thick and greenish rind
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(Wutscher and Smith, 1993). Potassium application to sweet orange increased rind thickness
and juice (%) (Ashraf et al., 2010). Ashkevari et al. (2010) applied 750, 1500, 2250 and 3000
g of K per tree and reported that 2250 g per tree markedly increased rind thickness of citrus
fruit.
Calcium (Ca) is an essential plant nutrient involved in many physiological processes in living
organisms involving enzyme activities and stabilizing cell membranes (Conway et al., 1994).
It also acts as anti-ripening and anti-senescence agent in fruit (Lester and Grusak, 1999). In
'Fortune' mandarin, preharvest applications of calcium nitrate improved fruit firmness (El-
Hilali et al., 2004). In Ca deficient tissues, the activity of polygalacturonase (PG) increases
resulting in the disintegration of cell walls and collapse of the affected tissues (Marschner,
1995). 'Kinnow' mandarin fruit treated with calcium nitrate before harvest had more juice
(%) when compared with control (Singh and Sharma, 2011).
Micronutrient applications are also well documented in improving fruit quality of citrus.
Foliar application of Boron significantly increased fruit weight (Ullah et al., 2012) and Zn
improved juice volume of Kinnow mandarin (Ashraf et al. 2012).
2.7.1.5.2 Biochemical fruit quality
Alva et al. (2006) found no significant effect of N application on juice quality of 'Hamlin'
orange, contrarily Koo (1988) reported that increasing N rates increased juice acidity in citrus
fruits. Saleem et al. (2008) reported a significant increase in TSS, TSS:TA, total sugars, and
AA concentrations of 'Blood Red' sweet orange by the application of LBU.
Dou et al. (2005) reported that P application to 'Flame' grapefruit reduced ascorbic acid and
total sugars contents. El-Hilali et al. (2004) found that acidity contents decreased by
preharvest applications of calcium nitrate to 'Fortune' mandarin fruit.
Potassium application increased TSS, TSS:TA ratio and ascorbic acid and reduced acidity
(%) of juice (Ashraf et al., 2010). Fruit biochemical quality parameters like TSS, acidity and
ascorbic acid were improved, while TSS:TA ratio were reduced by K applications
(Ashkevari et al., 2010). El-Hilali et al. (2004) reported that preharvest K application
increased acidity of 'Fortune' mandarin fruit. El-Otmani (2004) reported that KNO3
application to 'Clementine' mandarin increased maturity index during off year while on year
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25
it increased TA and ascorbic acid concentrations of fruits. Dou et al. (2005) applied 0, 186
and 372 kg of K ha-1
to 'Flame' grapefruit trees and reported that K reduced rind colour
development, lycopene and β-carotene contents while increased ascorbic acid and total
sugars contents.
Foliar application of Zn improved TSS, TA, pH and ascorbic acid (Ashraf et al., 2012) and
boron improved TSS:TA ratio, ascorbic acid and total sugars of Kinnow mandarin fruit
(Ullah et al., 2012)
Overall, both macro and micro nutrients appears to influence fruit external and internal
quality parameters. However, very little work is done on nutrient management of young
Kinnow orchards. Nutrient differences between young and old trees, might be the reason of
poor fruit quality in young orchards. A comparison of endogenous nutrient concentrations of
various age groups is prerequisite to develop nutrient management strategies for young
orchards.
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Chapter-3
GENERAL MATERIALS AND METHODS
These research studies were conducted during 2007-2011, and comprised of two parts:
1. Investigating the basis of poor fruit quality in young orchards
2. Improving fruit quality of young orchards
In part one i.e. investigating the basis of poor fruit quality in young orchards following three
experiments was included:
Effect of tree age on fruit quality of 'Kinnow' mandarin
Effect of tree age and fruit size on storage potential of 'Kinnow' mandarin
'Kinnow' fruit growth and development in relation to changes in endogenous levels of
nutrients and pectin
The 2nd
part of the study i.e improving fruit quality of young orchards comprised of
following experiments:
Effect of timing of plant growth regulators application on fruit quality and storage
potential of 'Kinnow' mandarin
Exogenous applications of PGRs and nutrients on fruit quality of 'Kinnow' mandarin
General materials and methods are detailed as under, while specific information is given
under separate experiments.
3.1 Plant Material
All the experiments were conducted at a commercial citrus orchard in the main 'Kinnow'
mandarin growing district, Sargodha (latitude 32° 03ʹ N and longitude 72° 40ʹ