Bradyrhizobium improves nitrogen assimilation, osmotic adjustment and growth in contrasting cowpea cultivars under drought

Abstract

This study investigated the effect of inoculation with Bradyrhizobium spp. on nitrogen metabolism and growth of two contrasting Vigna unguiculata cultivars exposed to both inoculation and water deficit. The study was carried out in Universidade Federal Rural da Amazonia (01°27′S and 48°26′W). The plants remained in greenhouse environment. The experimental design used was completely randomised with 2 cultivars (drought tolerant and sensitive) combined with 2 water regimes (water deficit and control), and 2 inoculation treatments (inoculated and non-inoculated), totalizing 8 treatments. The variables evaluated were leaf relative water content, nitrate reductase activity, nitrogen compounds, and growth parameters. Results of this study showed that both cultivars presented increases in nitrate and proline, compared with non-inoculated plants. Water deficiency induced more intense reductions in shoot dry matter of non-inoculated plants, compared with inoculated plants. This investigation confirmed the hypothesis that inoculation with Bradyrhizobium improves nitrogen assimilation, osmotic adjustment and growth parameters in Vigna unguiculata plants.