Herbicidal activity of culture filtrates of Trichoderma spp. against two problematic weeds of wheat.

The herbicidal potential of culture filtrates of four Trichoderma spp., namely Trichoderma harzianum Rifai, Trichoderma pseudokoningii Rifai, Trichoderma reesei Simmons and Trichoderma viride Pers., was evaluated against two problematic weeds of wheat, Phalaris minor L. and Rumex dentatus L. In laboratory bioassays, generally, metabolites of all four Trichoderma species significantly reduced various root and shoot growth parameters of the two target weed species. The original concentrations of the culture filtrates of all Trichoderma spp., except T. harzianum, significantly reduced various parameters of root and shoot growth of wheat seedlings. In a foliar spray bioassay, the culture filtrates of all four Trichoderma spp. significantly diminished root and shoot biomass of R. dentatus. The effect of these filtrates on the shoot growth of P. minor and wheat was not significant. Culture filtrates of the four Trichoderma species were successively extracted with butanol, n-hexane, chloroform and ethyl acetate. In detached leaf injection bioassays, n-hexane fractions (3 mg mL(-1)) of T. pseudokoningii, T. reesei and T. viride, and ethyl acetate fractions of T. horzianum and T. pseudokoningii were found to be toxic against R. dentatus. This study concludes that the culture filtrates of Trichoderma species have herbicidal potential in the control of R. dentatus.