Studies On Mechanism Of Biocontrol Of Trichoderma. Spp Against Phytophthora Capsici

Pepper is one of the most important vegetables in china, and is of great cash crop. Pepper blight is a devastating disease, caused by Phytophthora capsici. P. capsici produces thick-wall oospores and they are able to survive in extreme environment. So pepper blight becomes one of best difficult soil-born diseases for controlling. Traditional chemical control have been main means and a lot of fungicides was used widely, which caused environment pollution as well as increasing of resistance of pathogen to fungicides. Recent research showed that Trichoderma spp. were able to control pepper blight but they did not involve in oospores of P. capsici. In this study, therefore, two Trichoderma strains obtained were used for studying superparasite and bioactivity against P. capsici, providing biocontrol strategy for pepper blight control and play the foundation for their application.1. Hyperparasitic activity of Trichoderma against P. capsiciBased on antagonism of Trichoderma spp. to P. capsici dual culture with P. capsici, best hyerparasitic train Thz01of T. asperellum was obtained, which was able to degradate hyphae of P. capsici completely within about7d. Antagonism of strain Thz01to oospores of P. capsici also was investigated by light microscopy and scanning electron microscopy. Under light microscopy, the number of oospores infected was investigated and they were20%,54.6%,70%and80%after5d,10,15and20, respectively. SEM observation showed that hyphae of T. asperellum were able to coil around and penetrate hyphae of P. capsici, indicating hyperparasitic mechanism of this strain to P. capsici.TEM observation showed that hyphae of T. asperellum was able to penetrate oogonium, produed a lot of hyphae between oogonia and oospores and caused the uter walls of oospores to invaginate, resulting in degradation of oospores eventually.2. Extraction, purification and identification of active metabolites Active metabolites against P. capsici were researched using Trichoderma viridescens strain TS0404stored in our lab. A large number of cultures from liquid and solid fermentation were extracted using ethyl acetate and about5g crude extract was acquired. Crude extract was purified with chromatographic column and thin layer chromatography(TLC),0.5g active fraction was obtained. The result of LC/MS analysis showed that there is at least two compound exsist in the active fraction.