Presentation on theme: "Effectiveness of Kenyan Rhizobia Strains on Soybean"— Presentation transcript:
1 Effectiveness of Kenyan Rhizobia Strains on Soybean Maureen N. Waswa, George M. Mwenda, Nancy K. Karanja, Paul Woomer and Fred Baijukyaputting rhizobiato work forKenyan smallholders farmers
2 JustificationBiodiversity and economic potential of African rhizobia is largely unexploredPotential exists for native rhizobia to outperform exotic commercial strainsObjectivesIdentify elite native rhizobia for soybeanCompare these rhizobia to standard industry strains
3 Steps in establishing rhizobia as elite strains Bio-prospecting and isolationAuthentication and preliminary screeningEffectiveness testing under greenhouse conditionsCompetitive abilities in potted soilField testing208 isolates186 isolates100 isolates24 isolates6 isolates
4 Greenhouse growth systems employed in this study non-quantitative, abandoned as unnecessaryLeonard jars with sand mediaThree liter pots with rhizobia-free vermiculiteclean controls, quantitative separation of isolatesGrowth pouches for MPNrapid estimation of native populationseffective isolates tested for competitive abilitiesThree liter pots with site soils
5 Greenhouse effectiveness testing of 100 isolates in 3 liter pots with rhizobia-free vermiculite Clockwise: early N response (top), sterile irrigation system (upper right), effectiveness differences (lower right) and experimental overview (lower left).
6 Effectiveness testing under greenhouse conditions Strains were compared by Effective Index and then assigned to four categories (< -N control, < 0.75 USDA 110, < USDA 110 and > USDA 110)
7 The best “candidate elite strains” emerging for greenhouse effectiveness testing isolateEIHostSource AEZNAK 1761.26CowpeaCoastal plainNAK 1791.25Eriosema sp.NAK 961.24SoybeanSemi-arid uplandNAK 1491.09NAK 1151.08soybeanSub-humid midlandNAK 1281.06USDA 1101.00USA (Industry standard)
8 Greenhouse competitiveness testing of 24 isolates in 3 litre pots with soil Clockwise: experimental overview (top right), MPN (lower left)and nodulation of test strain (lower right).2.7 x 103 rhizobia per g soil
9 The best promising elite strains emerging for greenhouse competitive ability testing IsolatesEIHostSource AEZNAK1281.00SoybeanSemi-arid uplandNAK1351.01NAK890.78NAK840.84NAK1151.03NAK1170.89USAD110USA (Industry standard)
11 8% 33% 38% 21% Competitive, highly effective Less competitive, highly effectiveCompetitive, less effectiveLess competitive, less effectiveNAK115NAK9NAK12NAK10NAK128NAK83NAK122NAK30NAK89NAK135NAK84NAK96NAK139NAK117NAK127NAK146NAK144NAK149NAK152NAK176 (SCcv)NAK176 (SB19)NAK160NAK179 (SCcv)NAK179 (SB19)NAK1618%33%38%21%
12 Conclusion and recommendation For strains to be elite, they must be screened for genetic stability, satisfactory growth and survival under inoculant manufacturing conditions.Preliminary testing of promising native strains have been done and further testing continues at the field with six promising native isolates.Competitive, highly effective and less competitive, highly effective: field testing should be done in different soils and environment.Isolates NAK179 and NAK176 performed well on promiscuous but not on specific soybean: Different inoculants maybe required for different soybean genotypes.