Phylogeny and Optimization of Trichoderma harzianum for Chitinase Production: Evaluation of Their Antifungal Behaviour against the Prominent Soil Borne Phyto-Pathogens of Temperate India

<i>Trichoderma</i> is the most commonly used fungal biocontrol agent throughout the world. In the present study, various <i>Trichoderma</i> isolates were isolated from different vegetable fields. In the isolated microflora, the colony edges varied from wavy to smooth. The mycelial forms were predominantly floccose with hyaline color and conidiophores among all the strains were highly branched. Based on morphological attributes, all the isolates were identified as <i>Trichoderma harzianum.</i> The molecular identification using multilocus sequencing ITS, <i>rpb2</i> and <i>tef</i>1α, genes further confirmed the morphological identification. The average chitinase activity varied from 1.13 units/mL to 3.38 units/mL among the various isolates, which increased linearly with temperature from 15 to 30 °C. There was an amplified production in the chitinase production in the presence of Mg⁺ and Ca²⁺ and Na⁺ metal ions, but the presence of certain ions was found to cause the down-regulated chitinase activity, i.e., Zn²⁺, Hg²⁺, Fe²⁺, Ag⁺ and K⁺. All the chitinase producing <i>Trichoderma</i> isolates inhibited the growth of tested pathogens viz., <i>Dematophora necatrix, Fusarium solani, Fusarium oxysporum</i> and <i>Pythium aphanidermatum</i> at 25% culture-free filtrate concentration under in vitro conditions. Also, under in vivo conditions, the lowest wilt incidence and highest disease control on <i>Fusarium oxysporum</i> was observed in isolate BT4 with mean wilt incidence and disease control of 21% and 48%, respectively. The <i>Trichoderma harzianum</i> identified in this study will be further used in formulation development for the management of diseases under field conditions.