Efficacy of a Combined Application of Trichoderma sp. and Bacillus velezensis B-27 in Suppressing Moler Disease in True Shallot Seed in Glasshouse

Abstract

Moler disease caused by Fusarium acutatum represents a major constraint in shallot production. The use of biological control agents has emerged as an environmental friendly disease management. This study aimed to evaluate the effectiveness of a combined application of Trichoderma sp. and Bacillus velezensis B-27 in suppressing moler disease and to assess its effects on plant growth and yield of shallots. The study consisted of in vitro antagonistic assays and in vivo glasshouse experiments using two shallot varieties derived from botanical seeds or true shallot seed (TSS). The observed parameters included pathogen growth inhibition, disease intensity, number of bulbs, bulb diameter, fresh bulb weight, and dry bulb weight. The results demonstrated that the combined biological agents effectively inhibited pathogen growth and significantly reduced moler disease intensity. Although several yield-related parameters did not differ significantly among treatments, the application of biological agents showed considerable potential as an eco-friendly and sustainable approach for managing moler disease in shallot cultivation.