Isolation And Identification Of The Pathogens Causing Potato Dry Rot Disease In Shanxi Province And Fungicides Screening

In this study, the main producing areas of Shanxi potato storage diseases were investigated, At the same disease-like pathogens were isolated, identified, and pathogenicity test were did, the main diseases of potato storage-dry rot,biological characteristics of its pathogens and the inhibitory effect on the five kinds of fungicides were studied. The results are summarized as follows:1. Survey results show that:There are four kinds of fungal diseases of potatoes in storage time(Rhizoctonia solani,Fusarium spp.,Alternaria solani,Streptomyces scabies);two kinds of bacterial diseases(Clavibacter michiganense subsp. Sepedonicus,Erwinia carotovora subsp.atroseptica).2. For six potato varieties disease survey found that:the lowest rate of susceptible varieties is Kexin 1st, the average incidence rate is 23.01%; the highest rate of susceptible varieties is Shepody, incidence rate is 50.87% on average.3. This paper identified:There are three kinds of pathogens that causing potato dry rot:Fusarium oxysporum、Fusarium acuminatum. Fusarium sambucinum. Among them, the optimum environment of mycelial growth of Fusarium oxysporum is 28℃, pH 8; Fusarium sambucinum is 25℃,pH为10; Fusatium acuminatum is 28℃,pH%8. In the use of carbon source:Fusarium oxysporum can make good use of soluble starch, Fusarium sambucinum can make good use of glucose, Fusarium acuminatum could make good use of soluble starch.In the use of nitrogen source:e fusarium oxysporum can produce better results in the use of peptone;Fusarium sambucinum use of ammonium sulfate poor, no significant difference for the other three nitrogen utilization; Fusarium acuminatum can make good effect on the use of peptone and urea,and no significant difference between them.4. five common broad-spectrum fungicide were selected for potato dry rot pathogen inhibition experiments indoors in this study. Growth rate method is used on the determination of inhibitory effect of five kinds of agents were tested on three kinds of mycelial growth and spore germination. Through the inhibition rate and EC50 in this experimental results, we know that the best inhibitory effect against three pathogens is carbendazim, the worst is mancozeb.5. The results of Fusarium oxysporum crude toxin showed that, potato seedling root activity can be reduced by Fusarium oxysporum crude toxin, and leaf relative conductivity higher, cell membrane permeability increases. With the extension of treatment time or crude toxin concentration increases, the impact of root activity and cell membrane permeability becomes bigger. The experiment of POD and PAL on Atlantic and Favorita showed, POD and PAL activity is closely related to the potato dry rot pathogen resistance; after infected Fusarium oxysporum crude toxin, the Atlantic has always been high activity in Favorita, and both POD activity curve was first decreased and then increased and then decreased, during 84h arrive peak; Atlantic PAL activity is higher than Favorita, and there are two activity peaks on Atlantic, but Favorita PAL activity appeared only once.