| Cabbage(Biassica oleracea L.)is a vegetable crop of the Brassicaceae Brassica genus,which are grown widely in China.In recent years,there have been reported black root disease about Cabbage in North China,black root disease harms cabbage seedlings and leads to death and reduction of cabbages.In order to further clarify the characteristics of the disease,study the types of pathogenic bacteria and their biological characteristics and screen the resistant materials.We collected cabbage disease samples at the Horticultural Station and Xiangyang Experimental Base of Northeast Agricultural University,and isolated the pathogenic bacteria by water agar method.Through the observation of morphology and molecular identification after purification,which combined with Koch’s law to determine the cabbage black root disease pathogenic bacteria and anastomosis groups,and explored the conditions that affect the growth of pathogenic mycelia.Finally,Orthogonal test was used to select the best artificial inoculation method.Three diseaseresistant varieties and twelve medium-resistant varieties of cabbage were screened by the inoculation method.The result of this study are as follows:(1)By observing a single strain(HB)isolated and purified from cabbages,it was initially determined to be Rhizoctonia solani.Pathogenicity testing and molecular identification showed that HB was responsible for the causative agent of cabbage black root disease,it can infect leaves in vitro and cause leaf rot.Phylogenetic tree results showed that HB was clustered with Rhizoctonia solani strains,and the closest relationship was the AG-4 HG I.(2)Biological characteristics research showed the most suitable conditions for mycelium growth were:continuous darkness,temperature 30 °C,p H value 8,the carbon source suitable for the growth of pathogenic bacteria was soluble starch and sucrose.The carbon source suitable for sclerotia production was mannitol,and the nitrogen source suitable for hypha growth was peptone and sodium nitrate,mycelial lethal temperature 46 °C.(3)Orthogonal test was used to select the best artificial inoculation method.We designed three-factors and three-levels,analysis of variance,and multiple comparison results showed that the main effect factor was seedling age.The inoculation method and concentration were second.As the concentration increases,the disease index decreases.The best inoculation method was the four-leaf stage and the root cut method.Inoculate a mycelium suspension at a concentration of0.025/m L.Thirty materials of Cabbage were screened by artificial inoculation method at the seedling stage.The disease resistance materials selected for the first screening were repeatedlyscreened to obtain three materials of disease-resistant(R),twelve materials of medium resistance(MR),eleven materials of susceptible(S)and four materials for easy susceptible(ES).The experiments identified the pathogens of Cabbage black root disease in Harbin,studied the biological characteristics of the pathogens,and screened out fifteen resistance materials of Cabbage.It is hoped to provide reference basis for the research on disease resistance breeding and field control of cabbage black root disease,and to lay the foundation for the study of disease resistance laws and disease resistance genes. |
