Effects of Bio-Stimulants, Bacillus Strains H30-3 and KJ40, on Drought Stress Alleviation and Suppression of Soft Rot on Napa Cabbage

Climate change has increased the frequency of abiotic stresses such as heat and drought, as well as biotic stresses, which significantly threaten various crop production such as corn, wheat and napa cabbage. We evaluated two biostimulant bacteria, Bacillus siamensis H30-3 and B. butanolivorans KJ40, for their ability to enhance drought stress tolerance in napa cabbage. In greenhouse assay, the microbial treatments increased fresh weight and regulated stomatal conductance, while reducing malondialdehyde accumulation, indicating alleviation of oxidative damage. When the two bio-stimulants were conducted in field experiment, the treated plants showed higher fresh weight, Normalized Difference Vegetation Index, and Photochemical Reflectance Index compared with the non-treated plants. Moreover, naturally occurring bacterial soft rot was reduced with control efficiencies of 47.5% for H30-3 and 63.8% for KJ40. These findings highlight the potential of H30-3 and KJ40 as bio-stimulant and biocontrol agents that can improve stress tolerance and disease suppression in napa cabbage.