Identification And Herbicidal Active Fraction Analysis Of Pestalotiopsis Microspora

It is well known that bioherbicides are suitable for requirement of the development of pesticide in the contemporary era.The usage of micro-organisms or microbial metabolites is an important approach in bioherbicides research and development.A phytopathogenic fungus with high herbicidal bioactivity was isolated from leaves of Phyllostachys pubescens and its formulation with high herbicidal bioactivity was studied in this paper. The main results are as follows:①A fungus was identified as the real pathogen of Phyllostachys pubescens by re-inoculation experiment.The strain was cultured in liquid medium,extracting crude toxin by abstraction,its crude toxin had high herbicidal bioactivity by bioassay.②According to its colony morphology and conidium characteristics and conidium germination site,the strain was identified as Pestalotiopsis by Professor Zhang Zhong-yi from Agricultural University of Yunnan.Then its DNA was extracted and amplified with specific primers corresponding to ITS1 and ITS4.The ITS fragment of 550 bp was deposited in GenBank database under accession number EU279435.The ITS sequence showed up to 95%homology with other ITS sequences of Pestalotiopsis,and it showed up to 100%homology with the ITS sequence of Pestalotiopsis microspora,so the strain was at last identified as Pestalotiopsis microspora.③The herbicidal bioactivity of P.microspora PM1 was the strongest among Pythium aphanidermatum AP1,Botrytis cinerea BC4 and Pestalotiopsis microspora PM1 by bioassay.④It could be found that the herbicidal bioactivity of its crude toxin extracted using ethyl acetate was the strongest among all tested extraction solvent and methods.The strain's fermentation conditions had also been optimized.P.microspora,which was inoculated into PD medium containing ferrous sulfate and cultueed at 15℃or 30℃for 15d in dark,owned the most strongest herbicidal bioactivity.⑤Results of weeding and crop safety test indicated that the herbicidal bioactivity of its crude toxin was strong,weeding extensive and could also cause big acreage necrosis on leaves of tomato,cucumber and bean,but no symptom on capsicum,maize and cotton. Component 6 with high herbicidal bioactivity were isolated from the culture filtrate of strain PM1 by TLC and CC,then fractionⅢwith high herbicidal bioactivity were isolated from the Component 6 by HPLC.⑥Aqueous solution with 20%,30%,35%,40%,50%crude toxin were stabile after stored at room temperature,-20℃and 54℃for 15h.The aqueous solution with 35% crude toxin had the strongest herbicidal bioactivity among them and better thermal stability than pure crude toxin.