Comparative Study of Antagonistic Effect of Soil-Derived Strains of Trichoderma harzianum Against Sclerotinia sclerotium (Lib). de Bary under In vitro Conditions

Abstract

Sclerotinia sclerotiorum (Lib.) de Bary is a soil-borne plant fungal pathogen with a broad host range and infects over 400 plant species at all growth and development stages. In chickpeas,it affects both the seedlings as they tend to collapse at the soil line and in grown up plants experience stem rot and non specific wilting. Trichoderma spp. act as an effective biocontrol agent for managing myriads of plant pathogens affecting various crops at different stages of growth. The research aimed to compare the antagonistic potential of lab-maintained Trichoderma harzianum strains (SV-1, SV-2, SV3, SV-14, SV-18, and IRRI-1) with those re-isolated from soil after intervals of 30, 60 and 90 days. Its already known that pathogens if subcultured for long suffer from attenuation in their virulence, on the similar lines we intended to determine whether some degree of loss in their antagonistic potential over the same strains inoculated and re-isolated from their natural ecological niche existed or so. In a dual culture assay, re-isolated strains demonstrated superior antagonistic effects on the pathogen's mycelial growth compared to lab-maintained counterparts. Notably, re-isolated strain SV-18 exhibited a 14.83% increase in antagonistic activity compared to the mother culture, while others showed an increase ranging from 6.99% to 9.32% after 30 days. Although the difference was slightly reduced after 60 days, it underscored the potential loss in antagonistic efficacy for Trichoderma harzianum strains subjected to decade long culturing and sub-culturing. Furthermore, a significant variation was reported in the inhibition %age between the re-isolations performed statistically as F(static) 46.3426 was reported to be much larger than the critical value. These findings highlight the significance of re-isolated strains outperforming in inhibiting the pathogen, emphasizing the importance of biocontrol agents functioning optimally in their natural ecological niches.