Genomic insights and biocontrol potential of endophytic Bacillus subtilis strain B_SP against fungal pathogen Colletotrichum gloeosporioides in Dioscorea alata L.
摘要
The endophytic bacterium Bacillus subtilis strain B_SP, isolated from the leaf tissue of the medicinal plant Aloe vera, was evaluated for its potential to mitigate anthracnose disease caused by a fungal pathogen Colletotrichum gloeosporioides in Dioscorea alata, an important tropical tuber crop. In vitro dual culture assays demonstrated that endophyte inhibited 85.5 ± 1.96% of C. gloeosporioides growth and showed strong antagonistic activity against other fungal phytopathogens including Fusarium falciforme, Phytophthora colocasiae and Sclerotium rolfsii. Conidial germination inhibition assays and microscopic examination of hyphal morphology provided further evidence of its biocontrol efficacy. The strain B_SP exhibited rapid and robust biofilm formation, peaking at 24 h, a key feature for facilitating effective colonization in host. Over three consecutive field seasons, soil application of endophyte significantly reduced anthracnose disease severity in greater yam by 47.17 ± 0.5%, resulting in tuber yields of 16.63 ± 3.5 t ha-1, comparable to standard fungicide treatments. Pot experiments in representative vegetable crops, chili and spinach, confirmed the isolate’s growth-promoting effects, with notable improvements in shoot and root length as well as biomass. Whole genome sequencing identified genes linked to antifungal activity, nutrient uptake, stress tolerance, and biofilm formation. Functional annotation and secondary metabolite analysis (antiSMASH and BAGEL4) revealed biosynthetic gene clusters encoding compounds such as subtilosin A, bacillibactin, plipastatin, pulcherriminic acid, bacillaene, competence and putative bacteriocins. These findings underscore the multifaceted potential of B. subtilis strain B_SP as a sustainable biocontrol agent and plant growth promoter, offering an eco-friendly approach for anthracnose disease management and crop yield enhancement across multiple species.