Abstract

Laboratory bioassays were conducted to screen and evaluate the potential herbicidal metabolites produced by Trichoderma.longibrachiatum (Tr673), T. harzianum (Tr319), T. viride (Tr347) T. koningii (Tr324) and T. asperellum (Tr85) on inhibiting seed germination (SGe) and shoot/root growth (SGr/RGr) of seedlings of Porslane (Portulaca oleracea), Barnyardgrass (Echinochloa crus-galli), and Amaranthus retroflexus L. The culture filtrates generated from fermented liquids with each of the Trichoderma strains were diluted into 10 and 20% by adding sterilized water, which was then applied onto the weed seeds individually. The IR (%) of SGr/RGr of seedlings were significantly higher (P≤ 0.05) in the treatments with Tr673 culture filtrate generated from potato dextrose broth (PDB) for all treated weed seeds compared to those in the treatments generated from other culture media with Tr673 or Tr347. The IR (%) on SGe and SGr/RGr of seedlings in the treatment with Tr673 culture filtrate generated from PDB + 0.4% sodium glutamate were significantly higher (P≤ 0.05) than those generated from PDB alone. The result of the bioassay with the crude extract (62.5 mgË‘L^-1) generated from Tr673 culture filtrate showed a similar effect on decreasing the SGr/RGr rates (%) of the weeds and cucumber compared to those with the chemical herbicide-glyphosate.

Key words: Trichoderma, herbicidal activity, metabolites, inhibiting, crude extract.