Trichoderma asperellum (NVTA2) as a potential antagonist for the management of stem rot in carnation under protected cultivation

In the present investigative study, fifty Trichoderma spp. (Persoon) were isolated from the rhizosphere of various crop plants. Their potential, as an antagonist was assessed against S. sclerotiorum (Lib.) de Bary, causing stem rot of carnation (Dianthus caryophyllus L.). T. asperellum (NVTA2) was superior in inhibiting the growth and development of stem rot pathogen up to 53.7 per cent in vitro. Seven Trichoderma species with greatest antagonistic potential were identified up to species level through molecular characterization. They were identified as T. asperellum (NVTA1, NVTA2), T. harzianum (NVTH1, NVTH2), T. citrinoviride (NVTC1, NVTC2), and T. erinaceum (NVTE1). Effective strains were screened for the presence of cellobiohydrolase (cbh1) and endochitinase (ech42) genes through PCR. Among the seven strains, T. asperellum (NVTA2) alone had both genes. Crude metabolite extracted from T. asperellum (NVTA2), effectively inhibited the mycelial growth of S. sclerotiorum up to 374.4 mm(2). GC/MS profiling of crude extract revealed the presence of antifungal compounds including aliphatic hydrocarbons, terpenes and fatty acids. Root dipping and soil application of talc formulations of the seven Trichoderma spp. revealed that T. asperellum (NVTA2) effectively suppressed disease incidence up to 11.8 (PDIPercent Disease Incidence) compared to the control (37.9 PDI), resulting in approximately 69% reduction. More over NVTA2 also promoted plant growth that resulted in increase in shoot numbers (6.60/plant), stalk length (72.7 cm) and flower yield (205.9 numbers/m(2)), which were comparatively greater than control.