Diversity of cultivable bacterial endophytes in Paullinia cupana and their potential for plant growth promotion and phytopathogen control

Abstract

Endophytic bacteria occupy the same niche of phytopathogens and may produce metabolites that induce the host plant systemic resistance and growth. Host and environmental variables often determine the endophytic community's structure and composition. In this study, we addressed whether the plant genotype, organ, and geographic location influence the structure, composition, and functionality of endophytic bacterial communities in Paullinia cupana. To characterize the communities and identify strains with potential application in agriculture, we analyzed two P. cupana genotypes cultivated in two cities of the State of Amazonas, Brazil. Endophytic bacteria were isolated from surface-disinfested root, leaf, and seed tissues through the fragmentation and maceration techniques. The colonization rate, number of bacteria, richness, diversity, and functional traits were determined. The plant growth-promoting ability of selected bacterial strains was assessed in Sorghum bicolor. We identified 95 bacterial species distributed in 29 genera and 3 phyla (Proteobacteria, Actinobacteria, and Firmicutes). The colonization rate, richness, diversity, and species composition varied across the plant organs; the last parameter also varied across the plant genotype and location. Some strains exhibited relevant plant growth-promoting traits and antagonistic traits against the main phytopathogens of P. cupana, but they were not separated by functional traits. The main bacterial strains with plant growth-promoting traits induced S. bicolor growth. Altogether, our findings open opportunities to study the application of isolated endophytic bacterial strains in the bioprospection of processes and products.

Keywords: Amazonia; Endophytes; Functional traits; Growth promotion; Hill’s series; Paullinia cupana.