Beneficial effects of microbial volatile organic compounds derived from Rhodopseudomonas palustris on plant growth and biological control

Microbial volatile organic compounds (mVOCs) play crucial roles in plant growth regulation and induce systemic resistance. Rhodopseudomonas palustris strain PS3 exhibits significant plant growth-promoting effects on various plants. This study aimed to elucidate the roles and mechanisms by which R. palustris mVOCs promote the growth of Arabidopsis thaliana and Chinese cabbage, and to explore their potential for biocontrol in Chinese cabbage.

Arabidopsis thaliana Col-0 and Chinese cabbage were cultivated to evaluate the plant growth-promoting traits and biocontrol activities of R. palustris mVOCs in both sterilized soil and natural soil. The compositions of mVOCs from PS3 and YSC3 strains were determined via GC‒MS, and the transcript levels in the plants and fungus were examined via RT‒qPCR.

PS3 mVOCs remarkably promoted A. thaliana growth, increasing fresh weight, root length, and lateral root numbers, while YSC3 mVOCs only increased the number of lateral roots. The most effective PS3 mVOCs were identified as nonadecane, hexadecane, and ethyl acetate, and nonadecane showed superior effects. PS3 mVOCs activated the expression of auxin-responsive genes (SAUR38 and EXP14) in A. thaliana. Additionally, treating Chinese cabbage with PS3 mVOCs not only promoted its growth but also helped suppress leaf spot disease caused by Alternaria alternata.

These findings suggest that PS3 mVOCs promote plant growth by influencing auxin-responsive genes to stimulate root development. It also inhibits fungal pathogens by suppressing melanin synthesis, reducing foliar diseases in leafy vegetables. These results suggest that PS3 mVOCs could serve as an effective biostimulant and biocontrol agent for improving crop health in sustainable agriculture.