Presentation given by Dennis Ochola, Bioversity International, on the 'Effect of Water Stress & the Interaction between Fertilizer & Inoculum Concentration'. The presentation was given at the International Horticultural Congress 2014.
Find out more at www.promusa.org
Read more about Dennis Ochola here:
http://www.bioversityinternational.org/about-us/who-we-are/staff-bios/single-details-bios/ochola-dennis/
Locating and isolating a gene, FISH, GISH, Chromosome walking and jumping, te...
Effect of Water Stress & the Interaction between Fertilizer & Inoculum Concentration
1. Effect of Water Stress & the Interaction
between Fertilizer & Inoculum Concentration
Dennis Ochola, Research Associate, Bioversity
International
International Horticultural Congress 2014 - 19th August
2. Content
Relevance of banana
Key constraints of
banana
Banana Xanthomonas wilt (BXW)
Soil nutrient depletion
Drought induced stress
Results 1: Water stress x BXW
Development
Results 2: Fertilizer x Inoculum concentration
x BXW
Conclusion
3. Relevance of bananas
• Banana is a versatile
food and income crop for
millions of smallholders
in EC Africa.
• Uganda #2 producer of
approx. 10 million
tonnes. Annual per
capita consumption
exceeds 300 kg.
• Continuous & reliable
production = Food
security (no drought-induced
famine). Erosion
Technoserve
Piet van Asten, IITA
5. Banana Xanthomonas Wilt
(BXW)
• Bacteria - Xanthomonas
campestris pv.
muscearum
(1.8 – 2.0 μ x 0.7-0.9μ)
• Devastating disease in EC
Africa; US$ 50 Million
losses.
• 1967 first noted on Enset
in the Ethiopian
highlands.
• Spread: Insects +
contaminated farm tools +
diseased suckers.
6. Drought induced stress
• Banana water req. >25 mm per
week = 1300 mm per year
(very sensitive to water stress).
• Most growing regions
experience suboptimal rainfall.
• CSIRO 2050: 100 mm rainfall
decline + 2 oC temperature rise.
• Drought = Δ Pathogen
suitability + Δ Crop
vulnerability.
YIELDS MIGHT
DECREASE BY
10-15%
7. Soil nutrient depletion
• Banana grown on Ferralsols +
Acrisols of low inherent
fertility.
• Crop is a heavy feeder i.e. 200-
400 kg N ha-1 N and 240-480 kg
K ha-1.
• Fertilizers not widely used =
high prices + limited and poor
access.
• Low fertility = reduced vigor +
high susceptibility to diseases.
8. Effect of Water
stress on BXW
Development
Research Question
Does duration & timing of water stress increase
susceptibility to Xanthomonas wilt?
9. Materials & Methods
• EAHB cv. Mbwazirume (persistent bracts + neuter flowers).
• 3.5 mm water per day until robust root system + leaves
• Water stress treatments – withholding water
• SF, 2W, 4W, SF+3W, 2W+3W and 2W+4W.
• Stress determined with a conventional water filled tensiometer DIK-
8333 pF meter.
• Inoculum and inoculation
• Xcm isolated + grown on Cellobiose Cephalexin Agar (CCA) (Mwebaze
et al. 2006)
• Bacterial colonies suspended in distilled water + OD adjusted to 0.5
approx. 1 x 108 colony forming units (cfu)mL-1) (Ocimati et al. 2013)
• 1 mL of Xcm injected in the petiole with the insulin syringe Micro-Fine+
0.33 x 12.7 mm.
10. Materials & Methods
• Disease development and wilt index
• Six-point scale (0-5) modified from Winstead & Kelman (1952)
0 = no wilt; 1 = 1 wilted leaf; 2 = 2-3 wilted leaves; 3 = 4 wilted leaves; 4 = All
leaves wilted; 5 = Dead or collapsed
• Percentage wilt index = [(0a + 1b + 2c + 3d + 4e + 5f/5n) x 100]
(Ssekiwoko et al. 2006)
• Incidence = proportion of plants expressing symptoms.
• Area under disease progress curve (Jeger & Viljanen-Rollinson, 2001)
AUDiPC + AUPSiPC
• Statistical analysis
• GENSTAT 11 Edition (VSNI, UK)
• ANOVA
• Mean separation LSD (P < 0.05)
11. Stress measurements with a pF
Meter
1.9
2.1
Moderate stress
2.3 2.3
2.8 2.8
3
2.5
2
1.5
1
0.5
0
SF 2W 4W SF+3W 2W+3W 4W+3W
pF value
Water stress treatments
Extreme
stress
Stress
free
12. BXW Parameters: Incubation
period
16.7 cd
13.6 b
15.6 c
12 a
15.1 bc
11.7 a
20
15
10
5
0
Incubation period (dpi)
Water stress treatments
13. BXW Parameters: Incidence
2268 a 2147 a
2735 ab2734 ab 2899 b
3162 bc
3500
3000
2500
2000
1500
1000
500
0
AUDiPC
Water stress treatments
14. BXW Parameters: % severity index
2735 ab
2268 a2147 a
3162 c
2734 b2899 bc
1400
1200
1000
800
600
400
200
0
AUPSiPC
Water stress treatments
15. Discussion & Conclusion
• Water stressed plants are physiologically weak = more
vulnerable to BXW. Hence BXW to be hastened by both
duration + timing of water stress.
• Increased incidence due to prolonged water stress
durations = shorter period Xcm to colonize the
parenchymatous tissue.
• Scenario in which BXW may be exacerbated by
changing climate, with effects large enough affect
smallholder production esp. in South-western Uganda.
• Temperature + rainfall data in 25 years show large
departures from normal.
16. Discussion & Conclusion
• Climate change-mediated impacts on plant diseases
and efficacy their management + productivity +
sustainability of agricultural systems (Chakraborty et al. 2000)
• Shifts in rainfall may alter host-pathogen interaction +
temperature spikes lead to breakdown of resistance.
• *Difficult to discriminate stress-induced from Xcm-inducing
wilting of banana.
• Xcm-induced wilting is due to reduced water + uptake
uptake due to embolism of the xylem from copious EPS
production.
17. Fertilizer &
Inoculum
Concentration &
BXW Development
Research Question
Does improved plant nutrition contribute to
increased Xanthomonas wilt resistance?
18. Materials & Methods
• EAHB cv. Mbwazirume (persistent bracts + neuter flowers).
• 3.5 mm water per day until robust root system + leaves
• 3 Fertilizer treatments – 0, 125 & 250 kg/ha
• 4 Inoculum treatments – 1 x 104, 1 x 106, 1 x 108 & 1 x 1012 cfu/mL
• Inoculum and inoculation
• Xcm isolated + grown on Cellobiose Cephalexin Agar (CCA) (Mwebaze
et al. 2006)
• Bacterial colonies suspended in distilled water + OD adjusted to 0.5
approx. 1 x 108 colony forming units (cfu)mL-1) (Ocimati et al. 2013)
• 1 mL of Xcm injected in the petiole with the insulin syringe Micro-Fine+
0.33 x 12.7 mm.
19. Materials & Methods
• Disease development and wilt index
• Six-point scale (0-5) modified from Winstead & Kelman (1952)
0 = no wilt; 1 = 1 wilted leaf; 2 = 2-3 wilted leaves; 3 = 4 wilted leaves; 4 = All
leaves wilted; 5 = Dead or collapsed
• Percentage wilt index = [(0a + 1b + 2c + 3d + 4e + 5f/5n) x 100]
(Ssekiwoko et al. 2006)
• Incidence = proportion of plants expressing symptoms.
• Area under disease progress curve (Jeger & Viljanen-Rollinson, 2001)
AUDiPC + AUPSiPC
• Statistical analysis
• GENSTAT 11 Edition (VSNI, UK)
• ANOVA
• Mean separation LSD (P < 0.05)
20. Fertilizer + Banana Growth
Fertilizer
Plant
height
(cm)
Pseudostem
Girth (cm)
Leaf Area
(cm2)
0 kg npk 89.9 13.4 953
125 kg npk 122.2 15.9 1589
250 kg npk 137.3 17.4 1722
Mean 116.5 15.5 1421
LSD (p<0.05) ** ** **
21. Fertilizer + Inoculum on BXW
Incidence
p<0.01 p>0.05
0npk 125npk 250npk
105
100
95
90
85
80
75
4e 6e 8e 12e
Incidence (%)
Log10 cfu mL-1
120
100
80
60
40
20
0
4e 6e 8e 12e
0npk 125npk 250npk
Fertilizer Treatment
22. Fertilizer + Inoculum on BXW
Severity
80
70
60
50
40
30
20
10
0
p<0.01 p>0.05
0npk 125npk 250npk
4e 6e 8e 12e
Wilt Index (%)
Log10 cfu mL-1
80
70
60
50
40
30
20
10
0
4e 6e 8e 12e
0npk 125npk 250npk
Fertilizer Treatment
23. Mortality (%)
Inoculum
(cfu mL-1)
Fertilizer Treatment
Meanx
0 125 250
104 15 ab 7.5 a 5.1 a 9.2 a
106 82.4 de 60.3 cd 72.7 d 71.8 d
108 65.4 d 80.8 de 79.5 de 75.2 de
1012 85.5 e 59.3 cd 67.9 d 70.9 d
Meany 62.1 d 52 c 56.3 cd
24. Discussion & Conclusion
• Fertilizers boost physiology of plants hence have
potential of augmenting disease resistance.
• Majority of cultivated East African highland bananas
have no resistance to Xcm infection.
• Xcm concentration has an overriding effect on the
effectiveness of fertilizers for BXW management.
• Type 3 effector proteins like YopJ-like C55 cysteine protease suppress
innate defenses in banana by enhancing nutrient uptake by Xcm.
• Findings contradict Atim et al. (2013) whereby
application of exogenous N, K+ & Ca2+ reduced BXW
susceptibility.
25. Discussion
• Studies reveal that fertilizers modulate predisposition to
facultative pathogens like Xanthomonas, Alternaria & Fusarium.
• Slow disease build up in 104 cfu/mL inoculated plants is
reminiscent of latent infections.
• Xcm survives latently in underground parts of banana mat
(corm) for 1-2 years (Ocimati et al. 2013)
• Prolonged duration of Xcm latency is associated with recent
resurgence of disease in fields wherein it had been
contained.
• Muted effect of fertilizer suggests a weak interaction with Xcm
concentration.
• Exercise caution prior to endorsements against fertilizer use in
BXW management.
COVER SLIDE
To change the picture:
Right click on the photo
Click on change picture
If you need a specific CRP logo, replace the general CGIAR logo at the upper right.
PARTNER LOGOS SLIDE
If you have 4 or more logos, place them on a separate slide like this.
TEXT + PICTURE ON THE RIGHT
To change the photo
-Right click on the photo
- Click on change
TEXT + PICTURE ON THE RIGHT
To change the photo
-Right click on the photo
- Click on change
TEXT + PICTURE ON THE RIGHT
To change the photo
-Right click on the photo
- Click on change
TEXT + PICTURE ON THE RIGHT
To change the photo
-Right click on the photo
- Click on change
TEXT + PICTURE ON THE RIGHT
To change the photo
-Right click on the photo
- Click on change
DIVIDER SLIDE
You can use it to introduce a section of your presentation.
SMARTART EXAMPLES
These are examples that you can change according to your needs. Please make sure to use the Bioversity International colour palette, automatically available in the colour selection as the first colour theme (first row).
SMARTART EXAMPLES
These are examples that you can change according to your needs. Please make sure to use the Bioversity International colour palette, automatically available in the colour selection as the first colour theme (first row).
TITLE AND TEXT
TITLE AND TEXT
TITLE AND TEXT
TITLE AND TEXT
SMARTART EXAMPLES
These are examples that you can change according to your needs. Please make sure to use the Bioversity International colour palette, automatically available in the colour selection as the first colour theme (first row).
SMARTART EXAMPLES
These are examples that you can change according to your needs. Please make sure to use the Bioversity International colour palette, automatically available in the colour selection as the first colour theme (first row).
DIVIDER SLIDE
You can use it to introduce a section of your presentation.
SMARTART EXAMPLES
These are examples that you can change according to your needs. Please make sure to use the Bioversity International colour palette, automatically available in the colour selection as the first colour theme (first row).
SMARTART EXAMPLES
These are examples that you can change according to your needs. Please make sure to use the Bioversity International colour palette, automatically available in the colour selection as the first colour theme (first row).
TITLE AND TEXT
TITLE AND TEXT
TITLE AND TEXT
TITLE AND TEXT
SMARTART EXAMPLES
These are examples that you can change according to your needs. Please make sure to use the Bioversity International colour palette, automatically available in the colour selection as the first colour theme (first row).
SMARTART EXAMPLES
These are examples that you can change according to your needs. Please make sure to use the Bioversity International colour palette, automatically available in the colour selection as the first colour theme (first row).