Diversity and plant growth-promoting traits of endophytic bacteria isolated from maize cropped in organic and low-input agricultural systems in southern Brazil.

Abstract

Plant growth-promoting bacteria (PGPB) may enhance plant growth and health through several mechanisms, contributing to sustainable agriculture. We isolated and characterized endophytic bacteria from stems of landrace maize (Zea mays L.) grown under low-input and organic systems in southern Brazil. The 16S rRNA analysis revealed 83 isolates within 14 genera, including α-Proteobacteria, β-Proteobacteria, γ-Proteobacteria, Actinomycetia and Bacilli classes. The synthesis of indolic compounds was widespread among the strains, as well as the enhancement of N concentration in N-free media, a putative trait for the capacity of biological nitrogen fixation. Phosphate solubilization prevailed in Burkholderia and Paraburkholderia strains, while siderophore production was observed in all genera except Microbacterium. Inoculation with selected strains confirmed growth promotion on maize plantlets, particularly Sphingomonas CNPSo 2378 and Bacillus velezensis CNPSo 2384, whose genomes were sequenced and revealed PGPB features and evolutionary relationships, shedding light on the diversity, functional traits and occurrence of PGPB in low-input and organic agricultural systems.