Indian J Microbiol. 2010 Oct;50(4):425-31. doi: 10.1007/s12088-011-0085-6. Epub 2011 Jan 30.
Two plant growth promoting rhizobacteria--Sinorhizobium meliloti RMP1 and Pseudomonas aeruginosa GRC(2) were studied for integrated nutrient management to obtain improved yield of Brassica juncea. Low concentrations of urea and diammonium phosphate (DAP) stimulated the growth of both S. meliloti RMP1 and P. aeruginosa GRC(2). 1 M of urea and 0.35 M of DAP was found lethal for RMP1, while 1.3 M and 0.37 M concentrations of urea and DAP proved to be toxic for GRC(2). Lc(50) was observed as 0.49 M of urea and 0.15 M of DAP for RMP1, and 0.66 M urea and 0.18 M of DAP for GRC(2). Urea and DAP adaptive variants of RMP1 and GRC(2) was isolated. Adaptive bacterial variants had better growth rates at sub-lethal (Lc(50)) concentrations of urea and DAP as compared to non-adaptive variants. They also retained plant growth promoting attributes similar to non adaptive variants. GRC(2) and RMP1 did not affect the growth of each other and were chemotactically active for DAP, urea as well as root exudates of B. juncea. Both the isolates colonized well in the rhizosphere of B. juncea, as their populations were recorded ≈5 log(10) cfu g(-1) after 120 days. Interestingly, the colonization ability was found even better when both strains were co-inoculated, as their population was recorded in the range of ≈6 log(10) cfu g(-1) after 120 days. In field trials, application of RMP1 and GRC(2) resulted in significant increase in biomass and yield of B. juncea as compared to control. However, yield was better with application of half dose and full dose of recommended fertilizers. Interestingly, the biomass as well as yield improved further when both isolates were applied together along with half dose of recommended fertilizers.
两种植物促生根瘤菌——根瘤菌 meliloti RMP1 和铜绿假单胞菌 GRC(2) 被研究用于综合养分管理，以提高芥菜的产量。低浓度的尿素和磷酸二铵（DAP）促进了 RMP1 和 GRC(2) 的生长。发现 1M 尿素和 0.35M DAP 对 RMP1 是致命的，而 1.3M 和 0.37M 浓度的尿素和 DAP 对 GRC(2) 是有毒的。观察到 RMP1 的 LC(50) 为 0.49M 尿素和 0.15M DAP，GRC(2) 的 LC(50) 为 0.66M 尿素和 0.18M DAP。从 RMP1 和 GRC(2) 中分离出了尿素和 DAP 适应性变体。与非适应性变体相比，适应性细菌变体在亚致死（LC(50)）浓度的尿素和 DAP 下具有更好的生长速度。它们还保留了与非适应性变体相似的植物生长促进特性。GRC(2) 和 RMP1 不会相互影响，并且对 DAP、尿素以及芥菜根分泌物表现出趋化活性。这两种分离物都能很好地定殖在芥菜的根际，在 120 天后，它们的种群记录约为 5log(10)cfu/g。有趣的是，当两种菌株同时接种时，发现它们的定殖能力甚至更好，在 120 天后，它们的种群记录在 6log(10)cfu/g 的范围内。在田间试验中，与对照相比，应用 RMP1 和 GRC(2) 可显著增加芥菜的生物量和产量。然而，在应用推荐肥料的半剂量和全剂量时，产量更好。有趣的是，当同时应用两种分离物并与推荐肥料的半剂量一起应用时，生物量和产量进一步提高。
