Study On The Screening And Mechanism Of The Extracts Of Medicinal Plant For Inhibiting Verticillium Dahliae And Botrytis Cinerea

Verticillium dahliae and Botrytis cinerea are crop pathogenic fungi.Cotton Verticillium wilt caused by V.dahliae and tobacco gray mold caused by B.cinerea are difficult to control and bring great losses to the development of agricultural economy.Botanical pesticides have the advantages of safety against natural enemies of humans,livestock and pests,not easy to develop resistance,safety to crops,wide sources,green environmental protection and pollution-free.Medicinal plant resources are abundant in China.Developing botanical pesticides using medicinal plants is one of the effective ways to alleviate a series of problems caused by chemical pesticides,such as increased resistance of bacteria,crop pesticide residues and environmental pollution.In this study,10 medicinal plants were selected to screen and study the antifungal activity of 7 common crop pathogenic fungi,and the medicinal plants with the strongest antifungal effect were studied in depth,providing theoretical support for the development of botanical pesticides.In this study,mycelium growth rate method was used to determine the antifungal activity of 10 medicinal plants against 7 crop pathogenic fungi in vitro,and in-depth study of the the strongest antifungal effect of medicinal plants: Rheum officinale.The effects of the water extract of R.officinale on the growth of cotton and tobacco were studied by irrigation method.Pot experiment and q PCR were used to detect the indoor control effect of water extract of R.officinale on cotton Verticillium wilt and tobacco gray mold respectively.The effect of water extract of R.officinale on spore germination of V.dahliae was studied by coculture method.Scanning electron microscopy was used to observe the effect of the water extract of R.officinale on mycelium morphology of V.dahliae and B.cinerea.The effect of the water extract of R.officinale on the conductivity of V.dahliae and B.cinerea was determined by conductivity meter.Effects of the water extract of R.officinale on resistance gene expression in cotton plants and tobacco were investigated by RT-q PCR.Malondialdehyde(MDA)content,peroxidase(PPO)and superoxide dismutase(SOD)activities of cotton and tobacco were determined by testing kits.The results were as follows:Some water extracts of medicinal plants had a broad spectrum of antifungal effects on pathogenic fungi,among which R.officinale had the strongest antifungal effect on V.dahliae with the antifungal rate of 100%,followed by the water extract of R.officinale on B.cinerea with a antifungal rate of 92.07%.Compared with the ethanol extract of R.officinale and the ethyl acetate extract of R.officinale,the water extract of R.officinale had the strongest inhibition rates on mycelium growth of V.dahliae and B.cinerea.The water extract of R.officinale could promote the growth of cotton.The water extract of R.officinale could significantly inhibit the reproduction amount of pathogenic fungi in the plant and effectively control cotton Verticillium wilt and tobacco gray mold.The water extract of R.officinale could inhibit the germination and mycelium formation of V.dahliae spores.The water extract of R.officinale could destroy the mycelial surface of V.dahliae and B.cinerea,cause their deformity.The water extract of R.officinale could stimulate the expression of resistance genes in cotton and tobacco.The water extract of R.officinale could reduce the content of MDA in cotton and tobacco,and enhance the enzyme activities of PPO and SOD,thus improving the resistance of plants.