Identification Of Pathogen Of Brown Spot Of Chinese Cabbage In Harbin

Brown spot is a leaf disease in Chinese cabbage.It has been reported that its pathogens are Cercospora brassicicola P.Hennings and Pseudomonas aeruginosa.In recent years,brown spot in Chinese cabbage was found in Harbin,Heilongjiang Province.The symptom of the disease was similar to white spot,but the color of brown spot was darker.At the early stage of the disease,there were brown spots on the leaves,most of which were round and occasionally irregular.The inside of the lesion was wheel-shaped,and thenthe lesion gradually expanded until it damaged the whole leaf.In the study,the purpose was to identify the pathogen of brown spot of Chinese cabbage in Harbin area through morphological and molecular identification,and to identify the host range,reinoculation and biological identification of the Fusarium equiseti.The results are as follows:1.Through the morphological identification of 7 pathogenic fungi isolated from brown spot,it was determined that the pathogen of brown spot belonged to Fusarium in Chinese cabbage.2.The pathogenicity test showed that the symptoms of the 7 strains of Fusarium were the same as those of the brown spot disease of Chinese cabbage in the field.3.By using ITS,EF1-α,and RPB2 genes,seven pathogens were identified.Strains 1,2,3,and 4 were identified as Fusarium equisetum,and strains 5,6,and 7 were Fusarium oxysporum.4.Through the identification of the host range of Fusarium equisetum,it was found that its host range was relatively wide,and it could infect crops of Gramineae,Leguminosae,Solanaceae,Cruciferae,Cucurbitaceae and Chenopodiaceae.5.The biological characteristics of Fusarium equisetum were identified,and the optimal growth conditions were as follows: 1)The suitable carbon sources were soluble starch,sodium carboxymethylate,xylose and no carbon source.2)The suitable nitrogen sources were sodium nitrate,glycine,and hydrolyzed casein.Ammonium sulfate is the most unsuitable nitrogen source,.3)The optimum temperature was 25 ℃～30 ℃.4)The suitable p H was 6-7.5)Light had little effect on the growth of hyphae.6)The lethal temperature of Fusarium equisetum strain was 61 ℃.