Antagonistic effect of 6-pentyl-alpha-pyrone produced by Trichoderma harzianum toward Fusarium moniliforme

The interactions between eight Trichoderma spp. isolates and Fusarium moniliforme were investigated. The results obtained from dual culture and the tests on volatile activity showed that the two isolates of T harzianum T23 and T16 exhibited considerable antagonistic potential. Quantitative analysis of 6-pentyl-alpha-pyrone (6PAP), purified from culture filtrate of T harzianum isolate T23, revealed that the optimal harvesting time for 6PAP production was 12 days post inoculation (dpi) (72.3 mg 1(-1)). In in vitro studies, 6PAP demonstrated potent inhibitory properties upon mycelial growth and sporulation of F. moniliforme in both volatile and non-volatile tests as well as on conidia germination and length of germ tubes. Mycelial growth was inhibited by 93.5% using 250 mu g ml(-1) of 6PAP. Conidia production of the target fungus was inhibited by 250 mu g ml(-1) of 6PAP in non-volatile and volatile assays by 98.0% and 78.6%, respectively. Germ tube growth was also inhibited by more than 94% using 300 mu g ml(-1) of 6PAP. The results obtained demonstrated that the metabolite 6PAP exhibited rather fungistatic than fungicidal effects.