Seasonal response of groundnut genotypes to arbuscular mycorrhiza - Bradyrhizobium inoculation

Abstract

Nine cultivars of groundnut (Arachis hypogaea L.) earlier shown to respond to arbuscular mycorrhiza (AM) in a soil poor in available N or P were studied in the same soil over three subsequent seasons for their response to AM (M) and Bradyrhizobium (R) singly or in combination (M + R). The responses were measured for six traits, namely, the percentage of root length colonized by AM (AMC), Root P, Biomass (BM), carbon dioxide exchange rate (CER), leaf nitrogen and pod yield. Differences in four treatments, namely control, M alone, R alone and (M + R) were statistically evaluated for those traits across the cultivars and seasons. High improvements over control were consistently recorded under (M + R) in experimental plots of 75 m2, particularly for yield though responses were generally genotype and season-dependent. A basis for explaining improved yield sustenance by dual inoculation with arbuscular mycorrhiza and Bradyrhizobium was provided by the significant correlation between AMC and root P and of yield with them in addition to the desirable correlations between CER, BM and Root P. The results provide ample reason for integrating AM schedules into breeding and agronomic approaches in programmes on stabilizing groundnut yields.