Performance of Bradyrhizobium and Bradyrhizobium–Azospirillum in alleviating the effects of water-restrictive conditions during the early stages of Arachis hypogaea growth

Abstract

The objective of the work is to evaluate whether Bradyrhizobium sp. SEMIA6144 and Azospirillum brasilense Az39 can be used for inoculation to mitigate the negative effect of water restriction on growth of Arachis hypogaea. In this study, nitrogenase activity was determined by measuring the H2 evolution in an open-flow system, and N and C concentration in plants were determined by Elemental Analyzer. Lipid peroxidation and polyamines (PA) levels were analyzed by HPLC. The results showed that the restrictive water condition (RWC) caused an 80% inhibition of the N fixation rate. Although both single and double inoculation favored peanut growth under RWC, the inoculation with SEMIA6144 was better. Peanut plants have higher numbers of nodules in the roots when inoculated with SEMIA6144 in the absence of Az39, although it was observed that the inoculation with Az39 favored root development thus allowing the appearance of more infection sites in peanut roots. In double inoculation, the demand for N in the peanut was met with greater effectiveness. PAs found in leaves were putrescine, spermidine, and spermine. The results show that SEMIA6144 inoculation reversed the negative effects of RWC on growth and nodulation peanut parameters. Simultaneous application of SEMIA6144 and Az39 improved early nodulation, efficiency in N fixation and total N, thus increasing the tolerance of A. hypogaea to RWC. Our findings provide new insights in the context of mixed inoculation and improvement of peanut production in a limited water environment.