Mwenda George M, Hill Yvette J, O'Hara Graham W, Reeve Wayne G, Howieson John G, Terpolilli Jason J
Legume Rhizobium Sciences, Food Futures Institute, Murdoch University, 90 South Street, Murdoch, WA 6150 Australia.
Present Address: Department of Primary Industries and Regional Development, 75 York Road, Northam, WA 6401 Australia.
Plant Soil. 2023;487(1-2):61-77. doi: 10.1007/s11104-023-05903-0. Epub 2023 Feb 3.
Inoculation of legumes with effective N-fixing rhizobia is a common practice to improve farming profitability and sustainability. To succeed, inoculant rhizobia must overcome competition for nodulation by resident soil rhizobia that fix N ineffectively. In Kenya, where (common bean) is inoculated with highly effective CIAT899 from Colombia, response to inoculation is low, possibly due to competition from ineffective resident soil rhizobia. Here, we evaluate the competitiveness of CIAT899 against diverse rhizobia isolated from cultivated Kenyan .
The ability of 28 Kenyan strains to nodulate this host when co-inoculated with CIAT899 was assessed. Rhizosphere competence of a subset of strains and the ability of seed inoculated CIAT899 to nodulate when sown into soil with pre-existing populations of rhizobia was analyzed.
Competitiveness varied widely, with only 27% of the test strains more competitive than CIAT899 at nodulating . While competitiveness did not correlate with symbiotic effectiveness, five strains were competitive against CIAT899 and symbiotically effective. In contrast, rhizosphere competence strongly correlated with competitiveness. Soil rhizobia had a position-dependent numerical advantage, outcompeting seed-inoculated CIAT899 for nodulation of unless the resident strain was poorly competitive.
Suboptimally effective rhizobia can outcompete CIAT899 for nodulation of . If these strains are widespread in Kenyan soils, they may largely explain the poor response to inoculation. The five competitive and effective strains characterized here are candidates for inoculant development and may prove better adapted to Kenyan conditions than CIAT899.
用能有效固氮的根瘤菌接种豆科植物是提高农业盈利能力和可持续性的常见做法。要取得成功，接种用的根瘤菌必须克服与土壤中固氮效率低的本地根瘤菌在结瘤方面的竞争。在肯尼亚，菜豆接种了来自哥伦比亚的高效根瘤菌CIAT899，但接种效果不佳，这可能是由于本地土壤中固氮效率低的根瘤菌的竞争所致。在此，我们评估了CIAT899与从肯尼亚种植的菜豆中分离出的多种根瘤菌的竞争力。
评估了28株肯尼亚菜豆根瘤菌菌株与CIAT899共同接种时使该宿主结瘤的能力。分析了一部分菌株的根际竞争力以及种子接种的CIAT899在播种到已存在根瘤菌种群的土壤中时使菜豆结瘤的能力。
竞争力差异很大，在使菜豆结瘤方面，只有27%的测试菌株比CIAT899更具竞争力。虽然竞争力与共生有效性无关，但有5株菌株与CIAT899竞争且共生有效。相比之下，根际竞争力与竞争力密切相关。土壤根瘤菌具有位置依赖性数量优势，除非本地菌株竞争力较弱，否则它们在菜豆结瘤方面会胜过种子接种的CIAT899。
共生有效性欠佳的根瘤菌在菜豆结瘤方面可能比CIAT899更具竞争力。如果这些菌株在肯尼亚土壤中广泛存在，它们可能在很大程度上解释了接种效果不佳的原因。此处鉴定出的5株具有竞争力且有效的菌株是接种剂开发的候选菌株，可能比CIAT899更适应肯尼亚的条件。
