Kutsaga releases a Katambora

Rhodes grass variety (G HR1) for

nematode management under

tighter rotations

Justify Shava and Privilage Makunde

CORESTA CONGRESS 2016

TOBACCO RESEARCH BOARD

KUTSAGA

Munyaradzi Shamudzarira

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PRESENTATION OUTLINE

• Introduction

• Variety Development

• Variety evaluation (Field trial)

• Results

• Conclusions

• Acknowledgements

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• Rhodes grass (Chloris gayana) introduced from the Cape Province in the early 1900s

• Important crop in soil structure management and root knot management

• Suppresses root-knot nematodes in tobacco farming systems

INTRODUCTION

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BACKGROUND

KM10 – AFTER GRASS KM10 – AFTER KM10

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BACKGROUND

• The grass used for 3 to 4 years before the next tobacco crop

• However, after the land redistribution, 3 to 4 year rotations not possible due to reduced land sizes

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BACKGROUND

• Additionally, grass out crossing in nature- gradual loss of RKN resistance over time

• Therefore necessary to address these limitations to RKN management

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OBJECT IVES

• To develop a grass with higher RKN

suppression ability for use in shorter rotations

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METHODOLOGY

1. Development of the variety

2. Greenhouse evaluation of the

variety

3. Field evaluation

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• Recurrent selection

• Intercrossing of the resistant selections

• Repeatedly inoculated with root-knot nematodes and assessed for RK in the greenhouse

Variety Development

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• Resistant segregants identified

• Resistant selections passed on to next cycle (6 cycles)

• New variety Grass High Root Knot Resistance 1 (G HR1) developed

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DESCRIPTION OF GRASS

CHARACTER LANDRACE G HR1

Leaf Colour Green ,purple tinged sheath Pale green speckled sheath

Growth Habit Prostate Stoloniferous

Overall

Appearance

Stemy, purple tinged

internodes

Stemy, white tinged to light

green internodes

Days to flower 90 90

Nematode

resistance

Good Excellent

Flower Colour Light purple Non-pigmented pale yellow

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DESCRIPTION OF GRASS

CHARACTER LANDRACE G HR1

Leaf Colour Green ,purple tinged sheath Pale green speckled sheath

Growth Habit Prostate Stoloniferous

Overall

Appearance

Stemy, purple tinged

internodes

Stemy, white tinged to light

green internodes

Days to flower 90 90

Nematode

resistance

Good Excellent

Flower Colour Light purple Non-pigmented pale yellow

GHR 1 Landrace

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DESCRIPTION OF GRASS

CHARACTER LANDRACE G HR1

Leaf Colour Green ,purple tinged sheath Pale green speckled sheath

Growth Habit Prostate Stoloniferous

Overall

Appearance

Stemy, purple tinged

internodes

Stemy, white tinged to light

green internodes

Days to flower 90 90

Nematode

resistance

Good Excellent

Flower Colour Light purple Non-pigmented pale yellow

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APPEARANCE OF G HR1

G HR1 Landrace

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APPEARANCE OF G HR1

G HR1 Landrace

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GREENHOUSE EVALUATION

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• G HR1 evaluated against the Landrace

• Done in 20 L microplots

• Inoculated with 5 000 RKN juveniles per

pot

Materials and Methods

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• Mean No of eggs/root system

• Destructive sampling and root

galling assessments done

Measurements

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Tobacco root galling scale

0

6

3 1

4 5 7

2

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Tobacco root galling scale

0

6

3 1

4 5 7

2

8

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RESULTS

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MEAN NO OF EGGS / PLANT

110 000

115 000

120 000

125 000

130 000

135 000

140 000

145 000

Landrace G HR1

Egg

cou

nts

a

b

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Nematode Host status of G HR1 vs Landrace

CV Egg count Mean gall

rating

%

resistance Landrace 143 417 1.1 65

G HR 1 122 989 0.53 93

F-PROBABILITY 0.02 0.04 0.01

SED 12 453 0.13 1.2

LSD 15345.1 0.32 20.3

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RELATIVE % CHANGES IN NEMATODE POPULATIONS

UNDER LANDRACE AND GHR1

Year/ Season

Length of grass

rotation

Landrace % change in

nematode

population

G HR1 % change in

nematode

population

1 185 000 - 185 000

2 143 417 -22.5 82 980 -55.1

3 82 980 -42.1 22 728 -72.6

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VARIETY EVALUATION (FIELD

TRIAL)

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Materials and Methods

• The study was conducted at Kutsaga Research Station

• Agro Ecological Region IIA of Zimbabwe, coordinates of 17˚ 54′ South and 31˚ 08′

• Elevation - 1496 m above sea level.

• Max and Min Temp. of 32˚C and 18˚C respectively.

• Average annual rainfall is 800 to 1000mm

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Design: RCBD. 2 x 3 Factorial with 6 replications(3 buckets/plot)

Factor 1 (Rotation)

1. Landrace

2. G HR1

Materials and Methods

Factor 2 (Rotation time)

1 Year

2 Years

3 Years

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Materials and Methods

• KM 10 (Susceptible) and K RK26R (Tolerant)

• Planted nematode susceptible KM10 for one season

• Bioassays done to determine nematode population.

• Tobacco crops planted sequentially for 3 yrs

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Measurements

• Tobacco root galling (year 1 to 3)

• Tobacco yield (year 1 to 3)

• Nematode population build up assessments

• Grass herbage and seed yield

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Measurements

• Tobacco root galling (year 1 to 3)

• Tobacco yield (year 1 to 3)

• Nematode population build up assessments

• Grass herbage and seed yield

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Data Analysis

• ANOVA – Gentsart 18th edition

• LSD mean seperation

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Results

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ROOT GALLING - AFTER 1 YEAR

0

2

4

6

8

KM10 K RK26R

Gal

l rat

ing

L.S.D = 0.2

Landrace G HR1

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TOBACCO YIELD (KG/HA) – 1 YEAR

0

500

1000

1500

2000

2500

KM10 K RK26R

Yie

ld

L.S.D = 119.1 Landrace G HR1

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Comparative gall ratings (year 2 and 3)

0

1

2

3

4

5

6

Year 2 Year 3 Year 2 Year 3

KM10 K RK26

Gal

l Rat

ing

L.S.D = 0.2

Landrace G HR1

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COMPARATIVE YIELD PERFORMANCE OF TOB. CV

2000

2200

2400

2600

2800

3000

3200

3400

Year 2 Year 3 Year 2 Year 3

KM10 K RK26

Yie

ld

L.S.D = 128.2 Landrace G HR1

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HERBAGE YIELD (TONNES/HA)

6.65

6.7

6.75

6.8

Landrace G HR1

6.7

6.8 H

erb

ag

e Y

ield

to

nn

es/

ha

LSD = 1.01

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SEED YIELD (KG/HA)

LSD = 302

0

200

400

600

800

1000

1200

Landrace G HR1

See

d Y

ield

(kg

/ha)

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Conclusion

• G HR1 suppressed root-knot nematodes better than the Landrace grass after a susceptible tobacco crop

• GHR1 in conjunction with a resistant cultivar provide better nematode control and yields

• GHR1 give better yields in a comparatively shorter rotation than Landrace

• G HR1 can be used under shortened rotations

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Recommendations

• It is therefore recommended that G

HR1 be used in shorter rotations of two

years since it has improved nematode

suppression capacity.

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Thank You

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