Screening Of Attenuated Strains And The Attenuate Mechanism For Fusarium Oxysporum F.sp. Cucumerinum Treated By Extracts Of The Rotten Root And Soil Of The Parsley

Cucumber wilt is one of the soil borne disease which is caused by fusarium oxysporumf.sp.cucumerinum, had strong ability of living. It can live in the soil, in the sick body and in the seed as mycelium and sclerotium and chlamydospore during the winter. It can survive5-6years or longer in the soil. In recent years, the problem of cucumber wilt is very outstanding with the continuous development of facility cultivation of cucumber production,the morbidity degree is serious day by day. In recent years, it is a new trend for scholars at home and abroad to apply plant allelopathy technology to prevent and control the disease. Allelopathic effect gets paid attention to by the scientific research in20years, but it is not commom to use allelopathic effect to filter the attenuated strains from pathogenic bacteria, the research of pathogenesis is not common too.In order to select the attenuated strains for Fusarium oxysporum f.sp. Cucumerinum (Foc) and pathogenicity stability of the attenuated strains, the allelopathy and changes of pathogenicity of cucumber plants were detected respectively after treated by different parsley rotten root and soil extracts on Fusarium oxysporum f. sp. cucumerinum. The Foc were treated from the first generation and the first generation to fifth generations with parsley rotten roots extracted by ethanol, acetone and aqueous respectively in medium conditions. In order to figure out attenuate mechanism of parsley different extracts from rotten roots on Fusarium oxysporum f. sp. cucumerinum (Foc), including detect the number of each generation bacteria spore and the spore germination rate the Foc, and excretivly fusarium acid content,pectic enzyme activity,cellulose enzyme activity,Beta-glycosidase enzymes activity and its correlation with pathogenicity.1. The study failed to screened attenuated strains after treated by different parsley rotten root and soil extracts on Fusarium oxysporum f. sp. cucumerinum on one generation. Different parsley rotten root and the parsley rotten root soil treatment showed the1st generation colony diameter of Foc by the strongest inhibition, and following inhibition weaked with the increase of the subculture generations. The colony diameter showed extract<extract contrast<total contrast. In the sixth generation the disease index of parsley rotten root which are soaked by ethanol extract、acetone extract and aqueous extract are58.67%,57.83%and61.67%; the disease index of parsley rottenroot soil which are soaked by ethanol extracts acetone extract and aqueous extract are59.17%,58.83%and62.67%.After treated with different extracts,if we compared the contrast with the total contrast,we find the disease index reduced, the pathogenicity reduced, but do not get to the range of attenuated strains.2. Screened3attenuated strains after treated by different parsley rotten root and soil extracts on Fusarium oxysporum f. sp. cucumerinum. The Foc were treated from the first generation to sixth generations with parsley rotten roots extracted by ethanol, acetone and aqueous respectively in medium conditions. They are respectively the parsley rotten root ethanol and acetone treatment in the fifth generation, the parsley rotten root soil ethanol treatment in the sixth generation. Colony diameter of Fusarium oxysporum f. sp. cucumerinum which is dealed with parsley rotten root and the parsley rotten root soil which are soaked by ethanol extract,acetone extract grows slowlier than the contrast; The disease index of the Fusarium oxysporum f. sp. cucumerinum generational declined by extract for continuous generations. The disease index of parsley rotten root ethanol extract、acetone extract reduced to4.17%,3.33%in the fifth generation and the Disease index of Parsley rotten Root Soil ethanol extract is9.17%in the sixth generation,which identify the attenuated strains of the Fusarium oxysporum f. sp. cucumerinum.3. Successive transfer culture6generation process,after treated by different parsley rotten root and soil extracts on the one generation Fusarium oxysporum f. sp. cucumerinumo, which reduced the number of spore and the spore germination rate and pathogen’s fusarium acid content and inhibitioned of cell wall degradation enzymes. Correlation analysis show that there are significant positive correlations between pathogenicity pectinase enzyme activities, but there is no clear relationship between pathogenicity and pathogen’s fusarium acid content and the cellulose enzyme activities and β-glycosidase enzymes activity.4. Successive transfer culture6generation process, the number of spore and the spore germination rate had reduced after treated by different parsley rotten root and soil extracts on each generation Fusarium oxysporum f. sp. cucumerinum, which reduced pathogen’s fusarium acid content and inhibitioned of cell wall degradation enzymes. Correlation anal-ysis show that there are significant or extremely significant positive correlation between pathogenicity and pathogen’s fusarium acid content and pectinase enzyme activity and β-glycosidase enzymes activity, but there is no clear relationship between pathogenicity and the cellulose enzyme activities.5. Attenuated strain of Foc named FOC-RE-5, FOC-RA-5and FOC-SE-6. Seven generations of successive transfer culture in the process, Extension rate of colony diameter of attenuated strain<FOC, Performanced good genetic stability. Disease index of FOC-RE-5, FOC-RA-5and FOC-SE-6average of8.12%,7.48%and13.26%, respectively,it showed a good pathogenicity stability in cucumber plants treated by FOC-RE-5,FOC-RA-5and FOC-SE-6respectively.