An antifungal compound from Trichoderma harzianum SQR-T037 effectively controls Fusarium wilt of cucumber in continuously cropped soil

The aim of this study was to separate antifungal compounds that could effectively be against Fusarium oxysporum f. sp. cucumerinum (FOC) and control Fusarium wilt of cucumber in continuously cropped soil, from a promising biocontrol agent Trichoderma harzianum SQR-T037. One purified antifungal compound was identified as 6-pentyl-α-pyrone (6PAP) using both mass spectrometry and nuclear magnetic resonance spectroscopy. Assay of antifungal activity with a series of 6PAP concentrations (50, 150, 250, 350 and 450 mg L−1) in medium showed that the antifungal activity increased as the concentration increased. At 350 mg L−1 of 6PAP, 73.7% of mycelia growth and 79.6% of conidia germination of FOC was inhibited as compared with the control. Additionally, at a 6PAP concentration of 150 mg L−1, sporulation and fusaric acid production (g g−1 dry mycelia) of FOC decreased by 88.0% and 52.68%, respectively. Furthermore, 6PAP, added as a rate of 350 mg per kg in cucumber continuously cropped soil, could decrease population of indigenous F. oxysporum by 41.2% and control Fusarium wilt of cucumber by 78.1–89.6%, and thus increase dry weight of cucumber seedlings by 60.0–92.6% in pot experiments. The results showed that 6PAP demonstrated antifungal activity against FOC and could control Fusarium wilt in cucumber continuously cropped soil.