Abstract：
Bradyrhizobia are the principal symbiotic partner of the leguminous plant and take active part in biological nitrogen-fixation. The present investigation explores the underlying competition among different strains during colonization in host roots. Six distinct GFP and RFP-tagged Bradyrhizobium strains were engineered to track them inside the peanut roots either independently or in combination. The Bradyrhizobium strains require different time-spans ranging from 4 to 21 days post-infection (dpi) for successful colonization which further varies in presence of another strain. While most of the individual strains enhanced the shoot and root dry weight, number of nodules, and nitrogen fixation capabilities of the host plants, no significant enhancement of plant growth and nodulation efficiency was observed when they were allowed to colonize in combinations. However, if among the combinations one strains is SEMIA 6144, the co-infection results in higher growth and nodulation efficiency of the hosts. From the competition experiments it has been found that Bradyrhizobium japonicum SEMIA 6144 was found to be the most dominant strain for effective nodulation in peanut. The extent of biofilm and exopolysaccharide (EPS) production by these isolates, individually or in combinations, were envisaged to correlate whether these parameters have any impact on the symbiotic association. But the extent of colonization, growth-promotion and nitrogen-fixation ability drastically lowered when a strain present together with other Bradyrhizobium strain. Therefore, it is imperative to understand the interaction between two co-inoculating Bradyrhizobium species for nodulation followed by plant growth promotion to develop suitable consortia for enhancing BNF in peanut and possibly for other legumes.
摘要：
缓生根瘤菌是豆科植物的主要共生伙伴，积极参与生物固氮。本研究探讨了在寄主根中定殖过程中不同菌株之间的潜在竞争。对六种不同的GFP和RFP标记的缓生根瘤菌菌株进行工程改造，以独立地或组合地在花生根内追踪它们。缓生根瘤菌菌株需要不同的时间跨度，在感染后（dpi）4至21天的范围内成功定殖，这在另一种菌株的存在下进一步变化。虽然大多数单个菌株增加了芽和根干重，结节数量,和寄主植物的固氮能力，当允许它们组合定殖时，没有观察到植物生长和结瘤效率的显着增强。然而,如果在组合中一个菌株是SEMIA6144,则共感染导致宿主的更高的生长和结瘤效率。从竞争实验中发现，日本根瘤菌SEMIA6144被发现是花生中有效结瘤的最主要菌株。这些分离物产生的生物膜和胞外多糖（EPS）的程度，单独或组合，被设想为关联这些参数是否对共生关联有任何影响。但是殖民的程度，当菌株与其他根瘤菌菌株一起存在时，生长促进和固氮能力大大降低。因此,必须了解两种共同接种的缓生根瘤菌之间的相互作用，以结瘤，然后促进植物生长，以开发合适的聚生体来增强花生和其他豆类的BNF。
