Identification Of Pathogen On Potato Scab And Chemical Control In Gansu

Potato is the fourth largest crop except wheat, rice and maize. Potato scab is the fourth big disease outside of potato blight, potato early blight and potato ring rot. There is more than one hundred years history from discovery to the present, but it was be putted less one’s attention. In recent years, the disease aroused people’s more wide concern with people’s higher and higher demand, because potato scab are increased year by year.The main purpose of this study was to identify the pathogen causing potato scab and to screen fungicides in door in order to control the disease in the field, as well as resistance of different varieties of potato scab investigation.The results are as follows:1. The results showed that all of the strains were divided into spiral strains (GP-1, GP-2, GP-3, GP-4, JB-1, JB-2) and straight strains (GH-1and GH-2). Six spiral pathogenic strains (GP-1, GP-2, GP-3, GP-4, JB-1and JB-2) were selected by different tests including potato tuber slice test, radish slice test and the pot tests.Two straight pathogenic strains (GH-1and GH-2) were selected by different tests including potato tuber slice test, radish slice test and the pot tests.Eigent strains were identified based on morphological, physiological, biochemical and16S rDNA sequence. The results showed that the spiral strains (GP-1, GP-2, GP-3, GP-4, JB-1and JB-2) were consistent with S.scabies87-22in terms of morphological, physiological, biochemical and16S rDNA sequence; however, straight strains (GH-1and GH-2) were consistent with S. griseus based on morphological and16S rDNA sequence, not using a single carbon source with raffinose or inositol. The results indicated that the pathogens of potato scab from Gansu at least included two pathogens:Streptomyces scabies and Streptomyces griseus。2. The biological characteristics under different conditions including temperature, pH, lethal temperature and so on were studied of strains GP-1and GH-1. The results showed that GP-1and GH-1grows fastest at30℃and did not grow in lower10℃or above40℃, the pathogen went dormant in lower10℃and infected potato as the temperature increased, and loses its activity in long-term40℃. The strains might grow at pH4.8～11and optimally in pH7～9, them could be killed under75～80℃for10min or70℃～75℃for20min. So, lethal temperature was75℃3.Toxicity tests of9fungicides were conducted using paper disc methode, The results showed that six fungicides:Pythium oligandrum,53.8%Cupric hydroxide2000,40%Streptomycin sulfate,80%carbendazim,58%Fubol and20%quintozene had inbibitional effect to Streptomyces. Pythium oligandrum and53.8%Cupric hydroxide2000had best control effects. The results indicated that toxicity tests and chemical control in the field were consistent, Pythium oligandrum worked best, the control effect of51.56%,53.8%Cupric hydroxide2000take second place with a control effect of40.96%,20%quintozene’s control effect was worst.4.Resistance screening were conducted by pot experiment and investigation in the field, cv.Dabaihua from Qinghai Province is best resistant, followed by Zhuangshu no.3, Longshu no.6and Longshu no.7had middle resistance level, and variety Longshu no.3. is susceptible.