Trichoderma spp. as a novel pathogen for maize post-flowering stalk rot in India

This study explores the role of Trichoderma species as causative agents of stalk rot in maize, representing the first documented case in India. The pathogens were isolated from the infected maize stalks collected from various regions, revealing three distinct Trichoderma isolates (HSRT46, HSRT47 and HSRT67), which exhibited variability in morphological traits such as colony color, mycelium type, pigmentation and conidial structures. Pathogenicity assays, conducted using the toothpick inoculation method, confirmed the virulence of the isolates, with lesion lengths ranging from 5 cm to 9 cm, with HSRT46 having the highest record. Molecular characterization using ITS-rDNA and TEF-1α sequencing identified the isolates as Trichoderma afroharzianum (HSRT46) and T. harzianum (HSRT47 and HSRT67). Phylogenetic analysis signified a close relationship with T. atrobrunneum and this finding revealed a dual role for Trichoderma, traditionally known for its biocontrol capabilities, which may act as opportunistic pathogens under favorable environmental conditions. This emphasizes the need for ongoing monitoring of Trichoderma populations in maize, particularly in rain-fed regions, to mitigate the potential impacts on crop health and yield. Future research should aim to identify the conditions that cause Trichoderma to transition from a symbiotic to a pathogenic role, thus supporting the development of effective disease management strategies for sustainable maize production in India.