EVALUATION OF Trichoderma spp. AND MYCORRHIZA ON GROWTH AND MANAGEMENT OF Pestalotiopsis theae CAUSING GREY BLIGHT IN TEA

Abstract

Tea is an economic important crop that provides revenue to farmers and contributes to Gross Domestic Product. Tea maintenance leaves are affected by the grey blight caused by Pestalotiopsis theae. Trichoderma species are soil fungus that freely colonizes plant roots as opportunistic, plant symbionts with ability to antagonize diseases with additional benefits to the host plant. Arbuscular mycorrhizal fungi provide relationship of symbiosis with plant roots where the host receives minerals nutrients while the fungus gets products of photosynthesis. The study evaluated population dynamics of Trichoderma spp. propagules in the soil and percentage colonization of mycorrhizal structures in tea roots. The impact of Trichoderma spp. and arbuscular mycorrhizal fungi on the development characteristics of selected tea clones and the investigation on Trichoderma spp. in-vitro antagonistic action on the Pestalotiopsis theae pathogen. In the nursery, Complete Randomized Block Design (CRBD) using three replications and eight treatments while In-vitro studies were conducted under Complete Randomized Design (CRD). Results after three and twelve months on the recovery of Trichoderma spp. varied significantly p<0.05) with different treatments T39, T39+AMF and T17 population was higher in clone AHP S15/10, TRFK 31/8 and TRFK 303/577. In twelve months, there was an increase in Trichoderma spp. population. Percentage recovery of Mycorrhizal structures (hyphae, arbuscules and vesicles) was higher with treatment T17+AMF, T4+AMF and AMF in clones AHP S15/10, TRFK 31/8, and TRFK 303/577. Population of mycorrhizal structures root colonization increased after twelve months. In all the treatments on three clones of tea, there was enhanced growth in the tested parameters (shoot length, shoot diameter, and root length). Overall growth increased in treatment T39+AMF, T4, T17+AMF, T39 and T4 in almost all the tested parameters on the different tea clones. Dry weights did not vary significantly (p<0.05) in all the treatments applied to three clones of tea. Antagonistic strains of isolates T17 and T4 have potentiality in controlling P. theae in dual culture while in volatile metabolites it was T4 and T39. To boost Trichoderma population, re-application may be done twice a year. Recommendation for extension of research in field conditions to include yield as a growth parameter. In situ studies on grey blight disease management should be carried out to ascertain bioagent control.