The Biodiversity Of Potato Fungus Pathogens During Storage Period And Study On Potato Brown Rot Caused By Doratomyces Stemonitis In Gansu Province

For the purpose of understanding the fungal diseases, pathogen species anddominant species on potato during storage period in Gansu Province, the samples ofdisease were collected in the major producing regions of Gansu Province, thepathogens were identified through morphological characteristics as well as rDNA-ITSsequences. The biological characteristics, toxicity determination, the screening ofantagonistic bacteria and resistance to brown rot caused by Doratomyces stemonitiswere investigated in this article. The results could be summarized as follows:1Identification of the pathogens of main potato fungal disease during the storageperiod in Gansu ProvinceThe results were that the12species of fungi caused6types of potato tuberdiseases during its storage periods were identified as Fusarium solani、F. oxysporum、F. equiseti、F. tricinctum、F. spp、Rhizoctonia solani kuhn、Doratomyces stemonitis、Colletotrichum coccodes、Phoma foveata and Phytophthora infestans. The mostserious disease happened was dry rot, and then late blight, black scurf. The fungi mostfrequently isolated from dry dot potatoes were Fusarium solani and F. equiseti,frequencies of isolates were41.67%and28.57%.2The biological characteristics of Doratomyces stemonitisThe biological characteristics showed that the optimum temperature of themycelia growth was25-30°C and pH6. The pathogen could use monosaccharide,disaccharide, polysaccharide and the best carbon source was sucrose, and the bestnitrogen source was glycine. Illumination had no obvious promotion effect on themycelia growth. The optimum temperature for sporangium sprout was25°C and pH7.Spores could germinate only in water drop. The filtrate of potato and glucose solutionhad obvious promotion effect on spore germination. Soil solution had no effect onspore germination.3The toxicity tests of seven fungicides against Doratomyces stemonitisThe toxicity determination results showed that the EC50of10%DifenoconazoleWG,75%Chlorothalonil WP,70%Propineb WP were0.0068,0.0173and0.0184 mg·mL-1, which theoretically suggested that these fungicides could control the potatobrown rot caused by Doratomyces stemonitis.4Screening of the antagonistic organisms against Doratomyces stemonitis and theeffect of biocontrol bacteria to the germination of D. stemonitisEight species of biocontrol agents against potato brown rot were isolated, theexperimental results showed that the control efficacy of B1、B2were above73%respectively. S27、O72、O47were above70%. Through inhibiting spore germination,the results showed that their control efficacy were95.7～100%. The inhibition rate of10dilute inhibit filtrate were all above60%, which theoretically suggested that these10dilute inhibit filtrate could control potato brown rot caused by D. stemonitis.5The identification of resistance to D. stemonitis and the relationship betweenphysiological characteristics and resistance of D. stemonitis.The resistance comparison results showed that Qing shu9and Zhuang shu3wereresistant varieties, Long shu7and Qing shu168were middle-resistant varieties, Lishu7, Long shu3and Ding shu1were susceptible varieties.The relationship between physiological characteristics and resistance of D.stemonitis suggested that the activities of MDA and the resistances of brown rot werein negative correlations, the activities of POD, PPO, SOD had positive correlationswith the resistance of brown rot.