Abstract
Biological control agents (BCAs) represent a sustainable and environmentally benign alternative to synthetic chemical pesticides in modern agriculture. Among these, Streptomyces species are widely recognized for their ability to suppress phytopathogens and promote plant growth through diverse functional traits. In this study, a Streptomyces strain designated LZZY-S40 (=CGMCC No.30320) was evaluated for its antifungal activity using dual-culture assays and for its plant growth-promoting (PGP) potential through seedling growth assays and functional trait analysis. Genome mining and LC-MS-based metabolomic profiling were further performed to investigate its biosynthetic potential and secondary metabolite composition. Strain LZZY-S40 exhibited broad-spectrum antifungal activity against nine plant-pathogenic fungi, with inhibition rates ranging from 55.8% to 92.8%, the strongest suppression was observed against Exserohilum turcicum (92.8%). Further analyses indicated that strain LZZY-S40 is capable of producing extracellular proteases, suggesting a potential contribution to its antifungal activity. Genome mining identified several secondary metabolite biosynthetic gene clusters (BGCs) associated with the production of antimicrobial compounds, including those responsible for the biosynthesis of undecylprodigiosin and manumycin A. These genomic predictions were corroborated by LC-MS analysis. In addition to its antifungal properties, strain LZZY-S40 significantly enhanced the growth of wheat seedlings. At a concentration of 10(5) CFU·ml(-1), it increased root length by 88.3%, shoot length by 37.9%, and fresh weight by 32.1%. Consistent with these phenotypic effects, the strain tested positive for multiple well-established PGP traits-including indole-3-acetic acid (IAA) production, siderophore secretion, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, and nitrogenase-mediated nitrogen fixation-providing mechanistic support for its growth-enhancing capacity. Collectively, these findings demonstrate that strain LZZY-S40 exhibits robust antifungal activity against a broad spectrum of plant-pathogenic fungi and promotes plant growth significantly. Mechanistic investigations provided preliminary insights into the strain's antifungal and plant growth-promoting traits, contributing to a better understanding of its potential as a dual-action biocontrol agent.