Isolation And Identification Of A Mulberry Sclerotinia Sclerotiorum And Screening Of Plant-derived Bacteriostatic Agents

The most serious disease affecting mulberry production is sclerotinia sclerotiorum,which occurs at fruit mulberry cultivation bases throughout the country..Shaanxi province has a wide range of fruit mulberry cultivation.The mulberry fruit produced each year can bring huge economic benefits to the farmers.However,the yield of mulberry fruit is greatly affected by sclerotinia sclerotiorum,and once improperly controlled,it will reduce its production or even fail.It is generally believed that the original bacteria of mulberry sclerotinia Ciboria shiraiana,Ciboria carunculoides and Scleromitrula shiraiana,there are also studies that S.sclerotiorum can cause Sclerotinia.In order to carry out an in-depth study on the pathogen of mulberry sclerosis in Shaanxi Province,and lay the foundation for the subsequent biological control of mulberry sclerotinia.In this study,sporocarp with the characteristics of Sclerotinia sclerotiorum grown in the field during mulberry flowering period were collected,and the corresponding strains were separated and purified from the fruit bodies by tissue separation.Morphology of the fruit body phenotypes and the strains isolated and purified therefrom Observe,and then conduct molecular biological methods to identify the combination of the two to finally determine the species of strain.The growth rate method was used to study the biological characteristics of the isolated strains,the plate method and live inoculation method were used to determine the pathogenicity,and the plant-derived bacteriostatic agent of the pathogen was screened in the laboratory.The main results obtained were as follows:1.Using conventional tissue block separation method to separate and purify the fruiting bodies collected in Sangyuan,Zhouzhi County.Two purified strains were isolated.Morphological and molecular biological analysis results showed that the two strains were gray mold and Sclerotinia sclerotiorum.In this study,Sclerotinia sclerotiorum was selected as the test strain for subsequent experiments.2.The research results of the biological characteristics of Sclerotinia sclerotiorum showed that the bacterium grows best in the environment with a p H value of 3;it is conducive to the growth of the bacterium at 15 ?,and it can also coagulate the sclerotium normally at 4 ?.;Among the different carbon sources,fructose and glucose have the best utilization effect,and the utilization effect is the starch the worst;among the different nitrogen sources,the most suitable is yeast powder,and the utilization efficiency is the urea.3.The results of inoculation of mulberry leaves by the plate method showed that Sclerotinia sclerotiorum could cause the leaves to rot and produce white hyphae.The re-separation and identification of the hyphae confirmed the sclerotium sclerotiorum.Arabidopsis thaliana and tobacco were inoculated with test strains in vivo.After 24 hours of inoculation,the fungus covered the leaves to rot and a large number of white hyphae were re-separated and identified as Sclerotinia sclerotiorum.The mycelium and spore suspensions of the tested bacteria were used to infect the female flowers of the mulberry field,but the experiment was unsuccessful.4.Select 18 medicinal plants with antibacterial activity reported in the literature,use 60% alcohol extract as the test solution,and use the growth rate method to determine the inhibitory effect of test solutions from different plant sources on the Sclerotinia sclerotiorum.The results showed that among the 18 test plants,there were two kinds of extracts with a bacteriostatic rate of 0.1g / m L of plant dry powder exceeding 50%,namely star anise(97.21%)and magnolia(58.10%).A lower concentration of anti-bacterial test was conducted on star anise,and the results showed that when crude plant 0.09 g / m L was extracted,the antibacterial rate was 92.99%;0.08 g / m L was 63.84%;0.07 g / m L was 43.37%.After extracting and separating the star anise crude extract with water,toluene and ethyl acetate,the antibacterial test was performed on each part.The results showed that the antibacterial rates were water(89.72%),toluene(72.18%),ethyl acetate(36.67%)).