Biocontrol potential of native Trichoderma spp. against anthracnose of great millet (Sorghum bicolour L.) from Tarai and hill regions in India

Abstract Sorghum anthracnose, caused by Colletotrichum graminicola, is a destructive disease, and increasing dependency on chemical fungicides for its control has serious environmental concerns since sorghum is fed to cattle. Thus there is a need to develop effective bio-pesticide for biological control of C. graminicola. Since Trichoderma is a proven biocontrol agent against plant pathogens, exploring the greater diversity that exists in Trichoderma, could be of notable economic significance in terms of disease control. To harness the hidden potential of Trichoderma strains against C. graminicola, a study was undertaken with 20 Trichoderma spp. isolated from 40 rhizospheric soil samples. Dual plate antagonism assay indicated the potential of T3, T4, T6, T15, and T19 isolates of Trichoderma against C. graminicola, with T3 isolate showing maximum (76.47%) mycelial growth inhibition. Molecular characterization based on the sequence analysis of ITS-rRNA and tef-1α genes identified these isolates as Trichoderma asperellum and Trichoderma harzianum. Under the glasshouse condition, biopriming of seed with Trichoderma spp. had significantly decreased the percent disease index to 32.92% and helped improve plant growth-promoting attributes compared to untreated control. Seed biopriming with T3 isolate exhibited higher antioxidant enzyme activities in terms of superoxide dismutase (36.63%), peroxidase (43.59%), and polyphenol oxidase (40.96%) at 48 hours after pathogen inoculation. In most treatments, lignifications were highest in the epidermis, endodermis protophloem, metaphloem, pericycle, and protoxylem of sorghum roots after the 15th-day pathogen inoculation, indicating the strengthening of defense mechanism. To further evaluate, a field experiment was conducted for two consecutive years (Kharif season of 2018 and 2019) to test the best five isolates (T3, T4, T6, T15, and T19) against sorghum anthracnose. Lowest percent disease index of 54.90% and 53.68% and AUDPC value of 740.87 and 751.67 was reported from T. asperellum T3 bioprimed plants in the year 2018 and 2019, respectively, at 75 days after sowing. T. asperellum T3 isolate showed a significant increase in sorghum yield up to 22.22% and 27.29% higher than untreated control during the 2018 and 2019 Kharif season, respectively. This study indicated that T. asperellum T3 could be a potential biocontrol agent for managing the anthracnose of sorghum.