Performance of cowpea lines inoculated with Bradyrhizobium pachyrhizi based on the MGIDI index

Abstract

ABSTRACT Cowpea is a legume that holds significant importance in human nutrition. However, the national average yield is considered low, influenced by biotic and abiotic factors. The objective was to evaluate and select cowpea lines under the influence of Bradyrhizobium pachyrhizi as a nitrogen (N) alternative for multiple characteristics. Eight cowpea lines were evaluated at Campos dos Goytacazes-RJ, Brazil. A pot experiment in a factorial scheme 8x2x2, with eight lines, two levels of bacterial inoculation (B1 - seeds inoculated with B. pachyrhizi and B2 - seeds not inoculated with B. pachyrhizi), and two N levels (N1 - application of mineral N and N2 - no application of mineral N) was performed two times, from August to October 2020 and from November 2020 to January 2021. The design adopted was randomized blocks with four replications. A spacing of 0.5 m between rows and 0.3 m between plants was employed. The experimental unit comprised a 5-L pot filled with the commercial substrate Basaplant®. For N treatments, 5 g were supplied as urea. Shoot dry matter, root dry matter, root length, number of nodules, nodule weight, pod length, number of pods per plant, number of grains per plant, and grain weight per plant were evaluated. The GENES and R software were used for the analyses. The traits that showed the greatest gains were number of nodules, number of grains per plant, grain weight per plant, number of pods per plant, and nodule dry weight. Regardless of the application of mineral N, all lines that exhibited superior performance were those inoculated with B. pachyrhizi. These results demonstrate that inoculation constitutes an efficient and low-cost biotechnological alternative, capable of promoting significant productivity gains even under conditions of low N supply, reinforcing the potential of biological N₂ fixation as a sustainable strategy in crop management.