Agronomical Performance of Upland Rice Cultivars Inoculated with Azospirillum brasilense Depends on the Plant Genotype

Abstract

Plant growth–promoting bacteria may play an important role on rice development; however, its interaction with different genotypes is still uncertain. This work aimed to assess the effect of inoculation of Azospirillum brasilense AbV5 strain on the agronomical performance of different rice cultivars under field conditions during two consecutive years and to determine the response of rice cultivars to indole-acetic acid (IAA) rates under in vitro conditions using for both conditions a randomized block design. Field experiments evaluated the productivity components and grain yield of inoculated and noninoculated cultivars and in vitro assays monitored the plantlet growth under different IAA rates. Field experiments showed that the general average grain yield of rice cultivars inoculated with A. brasilense AbV5 strain was significantly greater. Fifty percent of the evaluated cultivars had statistically significant increase in yield varying from 40 to 108 percent upon inoculation with A. brasilense AbV5 strain, while 35 percent showed no significant change in yield (−6 to −28 percent). In vitro assays showed rate- and cultivar-dependent responses of upland rice to exogenous IAA. These results show a cultivar-dependent response of rice to inoculation with A. brasilense AbV5 strain, which can be related with IAA production by AbV5 strain.