Enhancing the rhizosphere colonization and persistence of plant growth-promoting rhizobacteria (PGPR) is necessary for maximizing PGPR-mediated benefits for crop growth and fitness in environmentally friendly agriculture. In the present investigation, we attempted manipulation of the rice rhizosphere by spraying of low molecular weight plant-regulating metabolites on the foliage of rice plants to in turn enhance the colonizing efficiency of soil-inoculated PGPR strain. The green fluorescent protein gene-tagged rhizobacterial strain, Pseudomonas chlororaphis ZSB15-M2, was inoculated in sterile plant growth medium (vermiculite coco peat mixture) and non-autoclaved agricultural soil. We sprayed different plant growth-regulating small molecules on the foliage of rice seedlings and monitored the colonizing efficiency of ZSB15-M2 in the rice rhizosphere. Among the chemicals assessed, salicylic acid (SA) at 1 mM or Corynebacterium glutamicum cell extract (CGCE, 0.2% w/v) or Saccharomyces cerevisiae cell extract (SCCE, 0.2% w/v) showed a tenfold increase in rhizosphere colony-forming units of ZSB15-M2 compared to control with a significant decline in non-rhizosphere bulk soil population. Foliar spray of CGCE enhanced soil organic carbon, microbial biomass carbon and soil protein by 21.86%, 9.68% and 11.57% respectively in the rice rhizosphere as compared to mock control. Additionally, CGCE spray enhanced the key soil enzymes, viz., dehydrogenase and acid- and alkaline phosphatase in the rhizosphere ranging 15–36%. The cumulative effect of this engineered rhizosphere resulted in the elevation of nitrogen, phosphorus, potassium and zinc availability by 21.83%, 28.83%, 23.95% and 61.94%, respectively, in rice rhizosphere as compared to control. On the other hand, SCCE and SA spray had an equal influence on the rhizosphere’s biological attributes, which is lower than that of GCGE and higher than that of mock control. From the study, we propose that the aboveground management of rice with microbial-based small molecules will modulate the rice rhizosphere to attract more beneficial PGPR-based inoculants, thus improving the crop and soil health.

增强根际定植和促进植物生长的根际细菌（PGPR）的持久性对于最大限度地利用PGPR介导的有益于农作物生长和环境友好型农业的益处是必要的。在本研究中，我们试图通过将低分子量植物调节代谢物喷洒在水稻叶片上来操纵水稻根际，进而提高土壤接种的PGPR菌株的定殖效率。绿色荧光蛋白基因标记的根瘤菌，绿假单胞菌将ZSB15-M2接种在无菌植物生长培养基（ver石可可泥炭混合物）和非高压灭菌的农业土壤中。我们在水稻幼苗的叶片上喷洒了不同的植物生长调节小分子，并监测了ZSB15-M2在水稻根际的定殖效率。在所评估的化学品中，水杨酸（SA）为1 mM或谷氨酸棒杆菌细胞提取物（CGCE，0.2％w / v）或酿酒酵母（Saccharomyces cerevisiae）细胞提取物（SCCE，0.2％w / v）显示，与对照相比，ZSB15-M2的根际菌落形成单位增加了十倍，非根际散装土壤种群显着减少。与模拟对照组相比，CGCE的叶面喷施使水稻根际土壤有机碳，微生物生物量碳和土壤蛋白质分别提高了21.86％，9.68％和11.57％。此外，CGCE喷雾增强了根际中的关键土壤酶，即脱氢酶以及酸性和碱性磷酸酶的浓度，范围为15–36％。与对照相比，这种工程根际的累积效应导致水稻根际的氮，磷，钾和锌的有效利用率分别提高了21.83％，28.83％，23.95％和61.94％。另一方面，SCCE和SA喷雾剂对根际的生物学特性具有相同的影响，低于GCGE且高于模拟对照。通过这项研究，我们建议使用基于微生物的小分子对水稻进行地上管理将调节水稻的根际，以吸引更多有益的基于PGPR的接种剂，从而改善作物和土壤健康。