Biocontrol of Fusarium wilt and induction of defense enzyme activities on cucumber by Trichoderma viride strain T23

Biocontrol of Cucumber Fusarium wilt with T. viride T23 was detected through bioassay, and its induction of several defense enzymes in cucumber was examined. Treatments with conidiospores and chlamy- dospores of T. viride T23 on cucumber seedlings reduced the disease index of Fusarium wilt from 33.69 to 13.12 and 10.28, respectively. The activities of defense enzymes, such as phenylalanine ammonia lyase (PAL), peroxidase (POD), polyphenol oxidase (PPO) and catalase(CAT), was measured in roots. Significantly higher levels of these enzymes were detected in T23-treated plants than in control.The maximum peaks of PAL, POD, PPO and CAT activities were enhanced by 2.75,2.49, 2.42 and 15.84 times over control, respectively, indicating that the production of phytoalexin or lignin might be involved in the disease suppression. The enzyme activities in conidiospore-treated cucumber reached their peaks earlier than those in chlamydospores treatment, however, the latter showed higher enzyme activity peaks in cucumber.