The Pathogenicity Of Seed-borne Fungi In Astragalus Sinicus Var.Yijiangzi And Fungicides Screening

Chinese milk vetch?Astragalus sinicus L.?is an important green manure and forage crop in China.It plays an increasingly important role in improving soil structure,improving fertility and ensuring livestock production.Seeds are important agricultural production materials,as propagation organs,they can carry fungi,bacteria,nematodes,etc.,and is an important way of spreading plant diseases.The Chinese milk vetch-Rice system is currently an important production model in China's rice grown areas,and some important diseases,such as Sclerotinia ciborioides,Cercospora astragali and other important diseases are becoming more and more serious,which has an impact on the stability of the system.All of the above diseases can be transmitted through seeds,so it is necessary to study the seed-borne fungi of Chinese milk vetch germplasm resources and to screen fungicides that could efficiently control the disease caused by the seed-borne pathogen of Chinese milk vetch.In this paper,Yijiangzi seed,an important variety of Chinese milk vetch in China,was used as a material to isolate and identify its seed-borne fungi,to study the effect of different seed-borne fungi on the germination and vitality of seeds,and to conduct fungicide tests in order to screen out the efficient fungicide to the seedborne pathogen.The main results are as follows:1.A total of 7 species belongs to 6 genera of seed-borne fungi were isolated from Yijiang seed.They were Alternaria tenuissima,Aspergillus niger,Curvularia affinis,Curvularia geniculate,Microdochium nivale,Pithomyces chartarum and Stemphylium vesicarium.2.The isolated seed-borne fungi can reduce the germination rate of Chinese milk vetch seeds,reduce the seed vigor index,and affect the growth of the plants.The germination rate of seeds inoculated with seed-borne fungi were decreased by1.69%⁷6.27%,the germination potential were decreased by 16.00%⁴2.00%,and C.geniculata and P.chartarum had the strongest and the least pathogenicity,respectively?P<0.05?.The germ length is reduced by 1.06%³4.39%,the pathogenicity ranked from high to low as M.nivale,S.vesicarium,C.affinis,C.geniculata,P.chartarum,A.niger and A.tenuissima?P<0.05?.The radicle length was reduced by 3.49%⁴3.02%,the pathogenicity ranked from high to low as S.vesicarium,M.nivale,C.geniculata,A.tenuissima,C.affinis,P.chartarum and A.niger?P<0.05?.Vitality index decreased by 2.25%⁷9.48%,C.geniculata and P.chartarum had the largest and smallest effects,respectively?P<0.05?.The rate of emergence was decreased by 15.79%⁵2.63%,the pathogenicity ranked from high to low as M.nivale,A.niger,A.tenuissima,S.vesicarium,P.chartarum,C.geniculata and C.affinis?P<0.05?.3.The virulence test results showed that the 5 tested fungicides can inhibit the 7species of fungi of the plant,of which,11%metalaxyl·fludioxoni·azoxystrobin,30%pyraclostrobin·tebuconazole,and 40%fluazinam·iprodione had good antifungal effect on the 7 kinds of seed-borne fungi with a correlation coefficient of 1.The EC₅₀values of 70%hymexazol was the largest,and the bacteriostatic effect was the worst.4.The effect of fungicides on the germination of seeds treated with seed-borne fungi were different.Among them,11%metalaxyl·fludioxoni·azoxystrobin,30%pyraclostrobin·tebuconazole and 40%fluazinam·iprodione respectively promoted the germination of seed-borne fungi with an average increase of 57.6%⁹0.45%,especially 11%metalaxyl·fludioxoni·azoxystrobin,which has the strongest pathogen inhibition?P<0.05?.In summary,the seed-borne fungi have a certain inhibitory effect on the germination rate,germination potential,and seed vigor of Chinese milk vetch seed.The use of fungicides has a certain inhibitory effect on the seed-borne fungi pathogen,which can promote the germination of inoculated seed-borne fungi seeds,and is expected to be used for seed treatment.