Grain quality and yield response of rice to application of plant growth-promoting bacteria and amino acids

Abstract

To investigate the effects of foliar application of plant growth-promoting bacteria (PGPB) and amino acids (AAs) on grain yield, nutrient concentrations and protein content of rice grain, a field experiment was conducted as a split-plot in a randomized complete block design with three replications during 2019-2020. The experimental treatments included the PGPB at five levels (control, P. agglomerans strain O4 (PGPB1), P. putida strain P13 + P. agglomerans strain P5 (PGPB2), P. koreensis strain S14 + P. vancouverensis strain S19 (PGPB3), and PGPB1 + PGPB2 + PGPB3 (PGPB4) as main plots and AAs at four levels (control, methionine, lysine, and methionine + lysine) as sub-plots. The results indicated that PGPB significantly enhanced the grain yield, protein content and nutrient uptake in rice grains when compared with control plants. However, the plants treated with co-application of PGPB strains (PGPB4) showed higher yield, higher protein accumulation and greater nutrients uptake such as N, P, K and Fe compared with individual application of PGPB strains and untreated plants. Among the separate application of PGPB strains, rice plants treated with PGPB1 with capability to N-fixing had the potential for enhance yield and improve protein and nutrients accumulation. The combined foliar application of AAs had greatest impact in increasing yield and improving rice grain quality in terms of protein content and uptake of nutrients, especially N, Ca and Fe in grain. Overall, our results suggest that co-applications of PGPB strains (PGPB4) and using a mixture of two AAs (methionine + lysine) may find value as plant growth-promoting for increasing rice yield and quality.