Assessment of the morphological, molecular and environmental adaptability of the native Trichoderma isolates for biocontrol applications

Abstract Trichoderma species are widely recognized for their biocontrol potential and ability to promote plant growth. This study aimed to evaluate the morphological, cultural, molecular, and antagonistic variability of native Trichoderma isolates under laboratory conditions. Six isolates were collected from different crops and agro ecological zones, and their growth characteristics were assessed using Trichoderma Selective Medium (TSM). Morphological characterization was conducted based on colony colour, morphology, pigmentation, concentric ring formation, and spore size, while molecular characterization using ITS marker analysis confirmed the genetic identity of the isolates. The results revealed considerable morphological and cultural variability among the isolates. Colony colours ranged from dark green to light green, with most showing rough, spongy, and raised morphology; two isolates (Tr 1 and Tr 2) exhibited prominent concentric ring formation, indicating higher sporulation. Reverse side pigmentation varied from dark brown to whitish creamy and pinkish, reflecting metabolic diversity. Spore sizes ranged from 3.06 × 2.92 µm (Tr 6) to 3.74 × 3.46 µm (Tr 3), showing moderate intraspecific variation. Despite these differences, PCR amplification of the ITS region consistently yielded a ~ 600 bp product across all isolates, confirming genetic uniformity within the Trichoderma genus. Environmental adaptability studies indicated that Trichoderma isolates thrived best at 30°C and in a pH range of 4.5–6.5, with significantly reduced growth under extreme conditions. In vitro antagonistic assays using the dual culture technique demonstrated that all isolates significantly inhibited the growth of major soil-borne pathogens including Sclerotium rolfsii, Macrophomina phaseolina, Alternaria alternata, Fusarium oxysporum, and Colletotrichum spp. The highest inhibition percentages were recorded with isolates Tr 1, Tr 2, and Tr 3, indicating their strong biocontrol efficacy. These findings underscore the potential of morphologically and genetically diverse native Trichoderma isolates as promising biocontrol agents under variable agro-climatic conditions, and support their integration into sustainable plant disease management strategies.