Agrochemical inputs and management have a greater impact on common bean rhizobia diversity than drought

Abstract Drought is one of the biggest problems for crop production and also affects the survival and persistence of soil rhizobia. The reduced presence of rhizobia limits the establishment of symbiosis and endangers the productivity of legumes, the main source of plant protein worldwide. Thus, the preservation of soil microbial diversity is essential because it can ameliorate crop response to stress by increasing the likelihood of the presence of stress-tolerant rhizobia and the chances of establishing effective symbiotic relationships. Aim Since the biodiversity can be affected by several factors including abiotic stress or cultural practices, the objective of this research was to evaluate the effect of water availability, plant genotypes and agricultural management on the presence, nodulation capacity and genotypic diversity of rhizobia. Method For that, a field experiment was conducted, with twelve common bean genotypes under irrigation and rain-fed conditions, both in conventional and organic management. Estimation of the number of viable rhizobia present in soils was performed before the crop establishment, whereas the nodule number and the strain diversity of nodule bacteria were determined at postharvest. Results Drought reduced the number of nodules and of isolated bacteria and their genetic diversity, although in a lesser extent than the agrochemical inputs related to conventional management. Conclusions Thus, the maintenance of diversity will be a key factor in the future, as problems caused by drought will be exacerbated by climate change.