Assessment of biological control candidates against Macrophomina phaseolina causing charcoal rot of sesame in Brazil

Abstract Sesame ( Sesamum indicum L.) has gained increasing economic importance in Brazil; however, its production is constrained by diseases such as charcoal rot, caused by Macrophomina phaseolina , a soilborne pathogen that is difficult to manage. Given the recent detection of this disease in Brazilian sesame-growing regions and the limited information available on biological management of this pathosystem, this study evaluated the antagonistic potential of microbial agents against M. phaseolina associated with sesame. Eight biological agents based on Bacillus , Priestia , and Trichoderma species were evaluated against three Brazilian isolates of the pathogen under in vitro conditions, followed by greenhouse evaluation of selected treatments for disease severity and a yield-related trait. In vitro assays showed that B. amyloliquefaciens , P. aryabhattai , B. velezensis , T. harzianum , and T. afroharzianum achieved near-complete or complete inhibition of mycelial growth, whereas the remaining agents exhibited intermediate levels of suppression. The antagonistic response did not differ significantly among the pathogen isolates evaluated. Under greenhouse conditions, microbial treatments significantly influenced the distribution of charcoal rot severity categories. Among the evaluated agents, B. amyloliquefaciens showed the lowest median disease severity score and the lowest estimated odds of occurrence of higher severity categories; however, its comparison with the M. phaseolina -inoculated control did not reach statistical significance at the 5% level. B. amyloliquefaciens also produced the highest number of capsules per plant among the evaluated treatments. These findings provide initial evidence supporting the potential of microbial agents, particularly B. amyloliquefaciens , as candidates for further evaluation in integrated management strategies for sesame charcoal rot.