Potential of Bacillus sp. SNRUSA4 for Plant Growth Promotion and Biological Control Against Bacterial and Fusarium Wilt in Tomato.

Tomato cultivation worldwide faces problems with bacterial wilt and Fusarium wilt, which cause significant yield losses. This study evaluated Bacillus sp. SNRUSA4, a polylactic acid (PLA)-degrading bacterium isolated from compost, for plant growth promotion and biocontrol against these diseases. In vitro assays confirmed that SNRUSA4 effectively inhibited Ralstonia solanacearum and Fusarium oxysporum f. sp. lycopersici, the pathogens responsible for bacterial wilt and Fusarium wilt, respectively. Important traits, including phosphate solubilization, nitrogen fixation, biofilm formation, and the production of siderophore, indole-3-acetic acid, ammonia, and hydrolytic enzymes (amylase, cellulase, lipase, protease, and chitinase), which are consistent with its PLA-degrading capability, were observed in SNRUSA4. These traits contribute to both plant growth promotion and disease suppression. The seedling tray experiment indicated that the combined application of SNRUSA4 and L-tryptophan synergistically promoted tomato seedling growth, enhancing shoot and root lengths. Seed priming with SNRUSA4 enhanced tomato seedling growth as shown in fresh weight, dry weight, and vigor index. SNRUSA4 demonstrated efficacy in the biocontrol of bacterial and Fusarium wilt diseases, along with promoting tomato growth in pot experiments. Thus, this study highlights the potential of Bacillus sp. SNRUSA4 as a multi-functional strain for bridging bioplastic waste management with tomato growth promotion and disease control.