Research On Identification Of Pathogens Of Leek Diseases In Puding And Prevention And Control Of Important Disease

In recent years,with the continuous increase in the supply of A.tuberosum in the market,many places have began to vigorously develop the A.tuberosum industry,the white flag of A.tuberosum in this county is a national geographical indication product and a gold industry for the local poor to get rid of poverty.However,due to the continuous expansion of planting area and the continuous planting in four seasons,the repeated infection and epidemic of various fungal diseases have led to the decline of yield and quality of A.tuberosum,which has caused great resistance to the sustainable development of A.tuberosum industry.At present,there are few systematic studies on the fungal diseases of A.tuberosum in Guizhou Province.Therefore,in this study,the fungal diseases of A.tuberosum in Puding County,Guizhou Province were investigated and collected.The pathogens were isolated and purified,and the pathogens were identified by pathogenicity determination,morphology and molecular systematics.The causes of various diseases on A.tuberosum were revealed,and the initial and epidemic periods of important diseases on A.tuberosum were preliminarily clarified.Subsequently,the indoor virulence determination and field efficacy test of the important disease pathogens of A.tuberosum were carried out to screen out chemical or biological agents with excellent control effect.Finally,the physiological and biochemical determination of the better pathogens was carried out to understand the mechanism of action of each agent,in order to provide reference for the scientific application of the main diseases of A.tuberosum.The main results are as follows:1.Disease investigation and pathogen identification.A total of 53 disease specimens were collected,13 strains were obtained,and 4 pathogens were identified,namely Botrytis squamosa,which can cause gray mold disease on A.tuberosum;Puccinia patriniae,causing A.tuberosum rust;Sclerotium rolfsii causes white silk disease in A.tuberosum;Alternaria cerealis,the first report of this pathogen causing A.tuberosum purple spot disease.According to the survey results from 2021 to 2022,Among them,rust and gray mold are main fungal diseases,causing widespread and serious damage;Sclerotium rolfsii took the second place and partially occurred;Purple spot disease occurs sporadically and causes minor damage.the initial onset of A.tuberosum rust is from August to September,and the epidemic period is from October to November;Gray mold can occur throughout the year if conditions are suitable;Sclerotium rolfsii can occur both with and without a sleeve,and the incidence is relatively severe during sleeve use.2.The antibacterial activity and field efficacy of fungicides against gray mold pathogens.The indoor toxicity test results of the 11 tested fungicides showed that 400g/L Flusilazole EC,12.8%Pyraclostrobin+25.2%Boscalid WG,50%Procymidone WP,20%Imazalil EW and 0.3%Tetramycin AS had better antibacterial effects against,and the EC₅₀were 0.1392,0.1416,0.5398,0.8358 and 2.2311 mg/L,respectively;.When 400 g/L Flusilazole EC with different mechanisms of action was mixed with50%Procymidone WP,the co-toxicity coefficient（CTC）was lower than 80,indicating an unsatisfactory synergistic effect.After treatment with12.8%Pyraclostrobin+25.2%Boscalid WG,50%Procymidone WP,and 20%Imazalil EW,PI staining showed red fluorescence,suggesting that the cell membrane of the gray mold pathogen may be damaged;The relative conductivity increased,the soluble protein content decreased,and the mycelium appeared deformation,top expansion,shrinkage,and content leakage,indicating that the integrity of the pathogen cell membrane was damaged,which caused the leakage of intracellular electrolytes and macromolecules,and ultimately led to cell death.The field control effect was carried out on gray mold,which were more serious in the field.The results showed that the field control effects of 12.8%Pyraclostrobin+25.2%Boscalid WG and 50%Procymidone WP had better field control effect on gray mold,and the control effects were 91.03%and 85.43%,respectively.3.The antibacterial activity of fungicides against Sclerotium rolfsii and their field efficacy against rust.The 9 tested drugs all had inhibitory effects on the mycelial growth of Sclerotium rolfsii.Among them,50%Fludioxonil WP,240g/L Thifluzamide SC and 0.3%Tetramycin AS had better antibacterial effects on Sclerotium rolfsii,and the EC₅₀were 0.1257mg/L,0.2667mg/L,and 1.8883 mg/L,respectively.The results showed that when the ratio of 240 g/L Thifluzamide:50%Fludioxonil was 8:2,9:1and 7:3,the co-toxicity coefficient（CTC）was 275.98,225.86 and 234.40,which had good bacteriostatic effect on Sclerotium rolfsii and showed strong synergistic effect.The optimal efficiency ratio treatment resulted in more severe deformities,local hyphae swelling,folds,depressions,and leakage of contents compared to single agent treatment,indicating that the cellular structure of the pathogen may be damaged;The PI staining results indicate that the cell membrane of the pathogen may be damaged;The increase in relative conductivity leads to a decrease in soluble protein content,suggesting that the synergistic combination may enhance the cell membrane permeability of the pathogen,inhibit protein synthesis,and affect the metabolism of pathogenic substances.The screening results of field fungicides for rust disease showed that all 8 fungicides had certain control effects on A.tuberosum rust,25%trifloxystrobin+50%tebuconazole WG and 12.5%Myclobutanil EC had good field control effects on rust,and the control effects were 60.69%and 43.44%,respectively.