new strategies to increase south african citrus export
TRANSCRIPT
New strategies to increase South African
citrus export volume and fruit quality
R Rosalie, OPJ Stander
J North & PJR Cronje
CRI and Department of Horticultural Science, SU
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Efficient use of sun light
• The only thing free in Citriculture is sun light
+ Heat & Light are necessary for: • Color development • Carbon assimilate
accumulation - ↗Heat & Light can cause:
• Damages • Fruit growth
restrictions • Fruit drop
Mandarin cv. Nadorcott
Shade Netting in Citrusdal
• Provide 20% shade • Decrease the light damage • Increase the photoactive period • Increase the water usage
efficiency
• Completely randomized experimental design • 4 Open Blocks • 4 Net Blocks
• Growing conditions measured: • Air temperature • Soil Temperature • Soil water potential • Relative humidity
O1
O4
N1
O3
O2
N4
N2
N3
Impacts of shade netting?
• Does is decrease or increase the temperature? • On one hand shade = lower
temperature • On the other hand green-
house effect
• What is the impact on color development? • Light is necessary for
normal color development • Temperature ≥ 35°C inhibit
carotenoid synthesis
• How do the trees allocate carbon under shade netting? • More growth or better fruit
yield and quality
Reproductive Growth Vegetative Growth
Sampling
• Every months from January to June
• 5 fruits per blocks
• Types of samples: • Albedo • Flavedo • Juice
• Analyses: • Detailed sugars (HPLC) • Detailed acids (HPLC) • Total polysaccharides
Growth conditions
0
5
10
15
20
25
30
35
40
8 13 18 23 28
Tem
per
atu
re (
°C)
Week
Max. and Min. Temperature Max_Open Max_Net Min_Open
Min_Net Average_Open Average_Net
-5
0
5
10
15
20
25
30
35
40
45
0:00 3:00 6:00 9:00 12:00 15:00 18:00 21:00 0:00
Tem
per
atu
re (
°C)
Time
Summer vs winter
Open_Warm Net_Warm
Open_Cold Net_Cold
Internal fruit quality
• Carbohydrates
• Seasonal accumulation
• No Net effect
• Acids
• Seasonal decrease
• Open blocks higher until low contents
0
20
40
60
80
100
120
140
160
Jan Feb Mar Apr May Jun
Tota
l Su
gar
(mg.
ml-1
)
Juice Open Net
*
*
0
20
40
60
80
100
120
140
160
180
Jan Feb Mar Apr May Jun
Tota
l Aci
d (
mg.
ml-1
)
Juice
Rind quality - Carbohydrates
*
*
20
40
60
80
100
120
140
0
100
200
300
400
500
600
janv. févr. mars avr. mai juin juil.Suga
r co
nte
nt
(mgG
lcEq
.gD
W-1
)
Free Sugars_Open Free Sugars__Net Polysaccharides_Open Polysacchirides_Net
*
*
20
40
60
80
100
120
140
0
50
100
150
200
250
300
350
400
janv. févr. mars avr. mai juin juil.Suga
r co
nte
nt
(mgG
lcEq
.gD
W-1
)
0
20
40
60
80
100
120
140
160
Jan Feb Mar Apr May Jun
Sucr
ose
(m
g.gD
W-1
) Albedo Open Net
*
*
*
0
10
20
30
40
50
60
70
80
90
Jan Feb Mar Apr May Jun
Sucr
ose
(m
g.gD
W-1
)
Flavedo
Rind quality - Pigments
• Chlorophyll and Carotenoid contents higher under Net on young fruits
• Colour break > Net/Open effect
• No pigment differences
*
*
*
0
0,2
0,4
0,6
0,8
1
1,2
1,4
1,6
1,8
2
janv. mars avr. juin
Pig
men
t co
nte
nt
(µg.
gDW
-1)
Chl A - Open Chl A - Net
Chl B - Open Chl B - Net
Carotenoids - Open Carotenoid - Net
Conclusion
• Net (20%) provides:
• Lower max soil T°C in summer and higher min soil T°C
• Higher water potential
• No effect on final internal quality
• Higher sugar accumulation in rind
• No effect on pigment contents
Further work
A bigger project including:
• Horticultural aspects : • Vegetative and reproductive growth • Yields • Fruit quality • Carbon allocation
• Soil science: • Water use efficiency • Soil composition
• Anthomology: • Insect distribution
• Plant pathology: • Pathogene distribution
Fruit irradiation and cold storage • Postharvest disinfestation of citrus fruit for False Codling Moth
mostly achieved through cold treatment (Hofmeyr et al. 1998)
• Current protocol of 22/24 days <0°C detrimental to fruit quality
• Chilling injury = Temperature x Exposure time
• Need for alternative disinfestation treatments with ensured fruit quality
• Irradiation of fruit an approved practise world wide e.g.
• USDA-APHIS approved irradiation as a quarantine treatment for fruits and vegetables in Oct. 2002
Citrus fruit response to irradiation range • Establish irradiation dose threshold for adverse fruit quality effects.
• Earlier exploratory trials indicated sensitive to the range of 200 to 500 Gy.
• 7 cultivars - export quality fruit-
• Star Ruby, Nules, Early/Late Navel, Turkey Valencia, Lemons and Nadorcott
• Exposed to 200, 300, 400 or 500 Gy
• Hepro: Cobalt irradiation source
• Cold stored at either 2 or 7°C for 40 60 d
• Evaluation for quality
• Rind disorder incidence
• Internal quality
• Taste test
Materials and methods
Results: Rind quality
05
101520253035404550
0 Gy -0.6°C
0 Gy2°C
200 Gy2°C
300 Gy2°C
400 Gy2°C
500 Gy2°C
0 Gy7°C
200 Gy7°C
300 Gy7°C
400 Gy7°C
500 Gy7°C
% P
itti
ng
Early Navel Pitting % - 40 Days
Pitting % - 60 Days
0
5
10
15
20
25
30
35
40
45
50
0 Gy -0.6°C
0 Gy2°C
200 Gy2°C
300 Gy2°C
400 Gy2°C
500 Gy2°C
0 Gy7°C
200 Gy7°C
300 Gy7°C
400 Gy7°C
500 Gy7°C
% P
itti
ng
Late Navels Pitting % - 40 d
Pitting % - 60 d
Results: Rind quality
0
5
10
15
20
25
30
35
40
45
50
0 Gy -0.6°C
0 Gy2°C
200 Gy2°C
300 Gy2°C
400 Gy2°C
500 Gy2°C
0 Gy7°C
200 Gy7°C
300 Gy7°C
400 Gy7°C
500 Gy7°C
% P
itti
ng
Star Ruby Pitting % - 40 Days
Pitting % - 60 Days
0
5
10
15
20
25
30
35
40
45
50
0 Gy -0.6°C
0 Gy2°C
200Gy 2°C
300Gy 2°C
400Gy 2°C
500Gy 2°C
0 Gy7°C
200Gy 7°C
300Gy 7°C
400Gy 7°C
500Gy 7°C
Pit
tin
g %
Turkey Valencia Pitting % - 40 d
Pitting % - 40 d
0
5
10
15
20
25
30
35
40
45
50
0 Gy -0.6°C
0 Gy2°C
200 Gy2°C
300 Gy2°C
400 Gy2°C
500 Gy2°C
0 Gy7°C
200 Gy7°C
300 Gy7°C
400 Gy7°C
500 Gy7°C
% P
itti
ng/
pet
eca
/sca
ldin
g
1st Lemon Pitting % - 40 Days Pitting % - 60 Days
Results: Rind quality
0
5
10
15
20
25
30
35
40
45
50
0 Gy -0.6°C
0 Gy2°C
200 Gy2°C
300 Gy2°C
400 Gy2°C
500 Gy2°C
0 Gy7°C
200 Gy7°C
300 Gy7°C
400 Gy7°C
500 Gy7°C
Pit
tin
g/p
etec
a/sc
ald
ing
2nd Lemons Pitting % - 40 d Pitting % - 40 d
Results: Rind quality
0
5
10
15
20
25
30
35
40
45
50
0 Gy -0.6°C
0 Gy2°C
200 Gy2°C
300 Gy2°C
400 Gy2°C
500 Gy2°C
0 Gy7°C
200 Gy7°C
300 Gy7°C
400 Gy7°C
500 Gy7°C
Pit
tin
g/st
ain
%
Nadorcott Mandarin Pitting % - 40 d
Pitting % - 60 d
0
5
10
15
20
25
30
35
40
45
50
0 Gy -0.6°C
0 Gy2°C
200 Gy2°C
300 Gy2°C
400 Gy2°C
500 Gy2°C
0 Gy7°C
200 Gy7°C
300 Gy7°C
400 Gy7°C
500 Gy7°C
% P
itti
ng
Nules Clementine Pitting % - 40 Days
Pitting % - 60 Days
Internal quality: no drastic changes expect lemons
Rind colour Juice % °Brix Cit. Acid
Star Ruby
Turkey Val
Lemon 1
Lemons 2
Navel Early
Navel Late
Nules Clementine
Nadorcott mandarin
Internal quality
0,00
0,20
0,40
0,60
0,80
1,00
1,20
1,40
1,60
1,80
0 Gy -0.6°C
0 Gy2°C
200 Gy2°C
300 Gy2°C
400 Gy2°C
500 Gy2°C
0 Gy7°C
200 Gy7°C
300 Gy7°C
400 Gy7°C
500 Gy7°C
Cit
ric
Aci
d
Turkey Valencia Citric Acid 40 days Citric Acid 60 days
4,80
5,00
5,20
5,40
5,60
5,80
6,00
6,20
6,40
6,60
0 Gy -0.6°C
0 Gy2°C
200 Gy2°C
300 Gy2°C
400 Gy2°C
500 Gy2°C
0 Gy7°C
200 Gy7°C
300 Gy7°C
400 Gy7°C
500 Gy7°C
Cit
ric
Aci
d
Lemon 1 Citric Acid Day 40 Citric Acid Day 60
0,00
1,00
2,00
3,00
4,00
5,00
6,00
7,00
0 Gy -0.6°C
0 Gy2°C
200Gy2°C
300Gy2°C
400Gy2°C
500Gy2°C
0 Gy7°C
200Gy7°C
300Gy7°C
400Gy7°C
500Gy7°C
Cit
ric
Aci
d
Lemon 2
• Only parameter effected - Citric acid in highly sensitive cultivars
• Reduction of Citric acid possibly due to increase in respiration
Conclusion and way forward
• Repeat irradiation in 2016 • Include Midknight and Nova mandarin
• Identify damaging level per cultivar group • Percentage and severity
• In general most cultivars OK <300Gy • Except Turkey<200Gy damaged • Of concern: Nadorcott and lemon
• Data will be used to motivate possible new combined protocol
Thank You
Any Questions?