Biocontrol Potential of Bacterial Isolates from the Caatinga Biome Against Charcoal Rot of Cowpea Caused by Macrophomina phaseolina

Abstract

Charcoal rot, caused by Macrophomina phaseolina, is one of the main difficult-to-control diseases that affect cowpea. Biocontrol has been gaining prominence for being an economically viable alternative with low risk to the environment. This study aimed to identify and evaluate bacterial isolates from the Caatinga biome for managing charcoal rot in cowpea. For this purpose, in vitro tests were performed, where the bacterial inhibition capacity under the growth of M. phaseolina strains was evaluated, and the production of non-volatile metabolites with an inhibitory effect on the mycelial growth of the fungus. In vivo tests, cowpea seeds were bacterized and sown in sterilized and natural soil with inoculum of M. phaseolina strains Fe 01 and Fe 02, for evaluation of Disease Severity Index (ISD%) and other growth variables and seedling development. Of the six isolates, four reduced more than 60% of fungal growth as well as their non-volatile metabolites. In vivo, the bacterium B. licheniformis FO5.7 applied to the seeds reduced the ISD% caused by M. phaseolina Fe 01 by more than 60% both in sterilized soil and in natural soil, and provided an increase in shoot and root mass, as well as the length of both. For M. phaseolina Fe 02, Bacillus sp. T 6.2 and M 7.1 reduced the severity in sterilized soil and positively influenced the growth and development of seedlings, however, they were not efficient in controlling the disease in natural soil.