Efficacy of Bacillus licheniformis: a biocontrol agent against Colletotrichum gloeosporioides Penz. (Penz. & Sacc.) causing anthracnose in greater yam (Dioscorea alata L.)

Abstract

Abstract Background Anthracnose, caused by Colletotrichum gloeosporioides, is the most dangerous fungal disease of greater yam (Dioscorea alata L.), and leads to significant crop loss. Microbial technology in cropping systems is currently focused on biological control agents (BCAs), which include plant endophytes like bacteria, which contribute well to sustainable production. In the present study, the ability of an endophytic bacterium, Bacillus licheniformis (CTCRI EB12), isolated from Aloe vera was investigated to prevent the disease. Results The bacterium, CTCRI EB12, was characterized as a member of the Bacillus genus by morphological and biochemical tests and confirmed as B. licheniformis via 16S ribosomal gene analysis. The effectiveness of the endophytic bacterium was affirmed through cell confrontation assays and scanning electron microscopy. In cell confrontation assay, the isolate inhibited all the three C. gloeosporioides isolates used in the study with more than 80% inhibition. The effect of culture filtrate of the isolate was also tested against pathogens that were compliant with the outcome of dual culture technique. The culture and culture filtrate could effectively restrain the spreading of C. gloeosporioides in greater yam leaf. The isolate could completely inhibit the growth of the pathogen through an antibiosis study, and the same could be explained through scanning electron microscopy results, in which the endophyte-treated C. gloeosporioides hyphae appeared longer and distorted compared to control and conidia possess disfigurement in endophyte-treated sample when compared to control. Conclusions The study showed that Bacillus licheniformis (CTCRI EB12), the endophytic bacterium that has the capacity to enhance the protection of greater yam plants, could be further developed as a microbial pesticide to reduce the effect of anthracnose in greater yam fields. Additional investigation will reveal the endophytic isolate's antifungal capabilities and assessment of their performance in the open field. The present study depicted that it might be a potent biological control agent against C. gloeosporioides causing greater yam anthracnose.

Keywords

• Colletotrichum gloeosporioides
• Endophytic bacteria
• Bacillus licheniformis
• Antibiosis
• Biocontrol
• SEM analysis