Growth promotion and management of Alternaria leaf spot in chilli by Trichoderma harzianum

Chilli (Capsicum annum) leaf spot caused by Alternaria solani is the most important, devastating and widespread disease in India. In vitro and greenhouse screening of Trichoderma harzianum isolates (T. har 25–92 and T. har 29–92) was conducted to investigate the plant growth promoting activities and inhibition against A. solani in chilli. Dual cultures of T. harzianum isolates and A. solani, with and without contact, were used as a mean to study the mycoparasitic response in T. har 25–92 and T. har 29–92. Both the isolates produced significant amount of chitinase and β-1, 3 glucanase in response to pathogen contact. Greenhouse studies indicated that T. har 25–92 and T. har 29–92 exert strong antagonistic activity against A. solani. Additionally, a significant increase in per cent seed germination and growth of chilli plants in terms of plant height, fresh weight, dry weight, and chlorophyll content was recorded. The induction in the level of total phenolic content and peroxidase activity by 1.5 to 3.0 fold in T. har 25–92 and T. har 29–92 treated plants indicates that these enzymes may have a role in the defense response against A. solani. Overall, the results suggest that these strains may be exploited for management of leaf spot and growth promotion in chilli.