Antagonistic Compound Screening And Biocontrol Agent Preparation Of Trichoderma Spp. For Controlling Pepper Blight

Pepper blight is a devastating disease caused by Phytophthora capsici, often leading to huge economic losses to pepper production. In recent years, the study found that some Trichoderma have a variety of mechanisms of antagonism to phytopathogen and can be used as effective biocontrol agents on plant disease. Therefore, in this study, we screened Trichoderma that can produce antagonistic compounds against Phytophthora capsici. Separation, purification and identification of these compounds were conducted and their biological activity was evaluated.Meantime,by using an acquired Trichoderma strain,preparation of biocontrol agents and field experiment have been carried out for the control of Pepper blight.1. Isolation, identification and bioactive determination of antagonistic compoundsTwo bioactive fraction separated from Trichoderma viridescens was identified as6-Pentyl-2H-pyran-2-one (6-pp) and α-phenylcinnamic acid by GC-MS, both of them are known compounds.Inhibitory effect showed that6-pp has the strongest inhibitory activitity against the mycelial growth of P. melonis following P. capsici, F. oxysporumand R. solani. Similarly, inhibitory effect of6-Pentyl-2H-pyran-2-one on zoosporangium germination of P. melonis is the best,following P. capsici. Inhibitory effect of6-Pentyl-2H-pyran-2-one on conidial germination of F. oxysporum and sclerotial formation of R. solani was confirmed as well.Although α-phenylcinnamic acid also markedly inhibit mycelial growth of P. capsici, P. melonis, and R. solani, it exhibited obviously difference from6-pp. When α-phenyl acid content of10μg were applied on the top of pathogen plugs (diameter5mm),it completely inhibited the mycelial growth of R. solani, when a-phenyl acid content was increased to20μg.plug-1, complete inhibitionof P. capsici and P. melonis mycelial growth was achieved. However,when the content to40μg, still not completely inhibit the mycelium growth of F. oxysporum.2. Wettable powder of T. asperellum with Conidia and biocontrol effect test The optimized formulation was determined as Trichoderma conidia powder30%, white carbon black20%, dispersing agent K129.1%, wetting agent DBS-Na12%, additive protective agent lecithin0.5%, and finally filled with bentonite to100%,with5.43×1010conidia·g-1, a germination rate of92.32%, moisture content of1.52%.The results showed that control effect for Pepper blight of wettable powder of Trichoderma was83.89%, the equivalent of the control effect of mandipropamid. The test results indicated that the wettable powder of Trichoderma had not only function of biological control, but also promotion of vegetable growth.