Isolation and screening of effective Trichoderma spp. against the root rot pathogen Macrophomina phaseolina.

The main emphasis of the present study was screened and evaluation of effective Trichoderma spp. for biocontrol of Macrophomina phaseolina the causative agent of root rot of groundnut. Five Trichoderma spp. were isolated from the rhizosphere soil of healthy groundnut plants, identified using morphological and microscopic characteristics and were evaluated for in vitro antifungal activity against M. phaseolina by dual culture plate technique and bioassay methods (in vitro antibiosis). Scanning electron microscopy was used to study the conidial surface of T. harzianum. Among the five isolates T. harzianum (T3), T.viride (T1) had maximum antifungal activity against M.phaseolina compared to the other Trichoderma spp. In dual culture technique T. viride and T. harzianum reduced mycelial growth by 61.1% and 64.4% respectively. Based on the dual culture technique, T. harzianum (T3), T. viride (T1) were selected for further research. Metabolites released from T. harzianum, T.viride were tested in culture medium against M.phaseolina. Cell free metabolites of T. viride, T. harzianum inhibited the growth of M. phaseolina in vitro and appeared to be fungicidal. The inhibition varied depending on the Trichoderma species producing metabolites, T. viride inhibited fungal growth upto 69% and T. harzianum upto 72.7% in nonvolatile and 47%, 64.7% in volatile metabolites respectively. The medium was optimized for mass multiplication of Trichoderma spp. T. harzianum, T. viride were tested for their ability to protect groundnut plants from disease caused by M. phaseolina in pot culture experiment. The growth of groundnut plants with the antagonist alone or in combination with pathogen was greater than in plants inoculated with pathogen alone.