Exploring the potentiality of botanicals and phyllosphere microbiome for the management of anthracnose disease in Black gram (Vigna mungo L. Hepper)

Black gram (Vigna mungo L. Hepper) is the third most important pulse crop, and its yield is reduced due to many diseases. Among them, anthracnose is one of the devasting global fungal diseases which cause severe damage. Use of fungicide is highly effective in controlling this disease, but continuous use of fungicides is unsafe for environment, and it causes fungicidal resistance. To overcome these problems, effect of plant extracts viz., Anisomeles malabarica, Azadirachta indica leaf extracts, phyllosphere antagonist Bacillus amyloliquifaciens, and essential oils viz., peppermint oil and lemon grass oil were evaluated against black gram anthracnose disease caused by Colletotrichum lindimuthianum under pot culture. Among the different treatments tested, plants sprayed with standard chemical viz., Carbendazim @ 0.2 percent recorded the least percent disease index (PDI) of 13.39 followed by A. malabarica leaf extract (10%) treatments, which recorded a PDI of 16.62, whereas plants treated with B. amyloliquifaciens, lemongrass oil and peppermint oil recorded a PDI of 20.91, 21.23 and 24.0, respectively, compared to the inoculated control (77.33 PDI). The induction of defense enzymes viz., phenol, peroxidase (PO), polyphenol oxidase (PPO) was recorded more (21.25 µg of catechol/g of leaf tissue, 3.82 changes in absorbance/min/g leaf tissue, 3.32 changes in absorbance/min/g leaf tissue, respectively) in the plants sprayed with A. malabarica. GC-MS analysis of hexane and ethanol extract of A. malabarica showed the presence of 26 phytocompounds. Among them, phenol 2,4- bis (1,1- dimethylethyl) phosphite from ethanol extract was a predominant compound (100%). Formulation and standardization of dosage for phenol 2,4- bis (1,1- dimethylethyl) phosphite compound will be useful for managing the disease effectively.