Native rhizobia from southern Brazilian grassland promote the growth of grasses

Abstract

Soil communities support great biodiversity, as well as their interaction with the plants, can be equally diverse. In this work, we focused our attention on investigating the effect of native rhizobia from Brazilian grassland as a plant growth-promoting rhizobacteria for grasses. We suggest that the positive effect of rhizobacteria on plants is context-dependent, and native species may present better adaptability under certain soil conditions (i.e. acidity, nutrient availability, interaction with other organisms in the rhizosphere). To explore this iteration among native rhizobia and grasses, we isolated rhizobia from Desmodium incanum, a native legume from Brazilian grassland, and inoculated on oats (Avena sativa) and maize (Zea mays). Firstly, we characterized the ability of those rhizobia in solubilizing phosphate and producing indole-acetic acid. Next, under greenhouse conditions, we inoculated grasses with the isolates that presented at least one mechanism of plant growth promotion. After 45 days, we measured the effect of those rhizobia on both morphological and nutritional attributes of grasses. Our finding showed that rhizobia isolated from Desmodium incanum improve the growth of grasses by increasing shoot and root biomass, plant height, and nutrient accumulation in leaves. The most efficient isolate was UFRGS-Dinc1, perhaps due to its ability in solubilize phosphate and produce indole-acetic acid. However, we also noted that UFRGS-Dinc3, that presented the highest phosphate solubilization index, and UFRGS-Dinc18, that produce only indole-acetic acid, could also promote plant growth of grasses. Our results provide pieces of evidence that native rhizobia from Desmodium incanum can promote the growth of grasses, indicating their potential in increasing the yield of crop cultures.