Studies On Biological Characteristic And Virulence Differentiation Of Alternaria Solani Causing Potato Early Blight

Potato early blight by Alternaria solani was more serious disease for potato. The disease infected leaves, stems and fruits which caused of the rot of potato storage, had a great influence on potato yield and quality. With the growing area of potato cultivation, potato early blight of study was more important. This study started from the pathogen identification, first of all studied the biological characteristics of Alternaria solani, after studied the virulence differentiation for Alternaria solani producing potato areas in Heilongjiang Province using inoculating detached leaves, and compared cultural characteristics for the different virulence strains.The purpose of these established the theoretical foundation for epidemiology, genetics and integrated control of potato early blight.The results are as follows:1. The mycelial linear growth rate method was used to study the suitable conditions for mycelial growth of Alternaria solani. The medium of PDA, temperature of 25℃, pH 6～8 were favorable to their growth. The suitable light and UV had promotion for mycelial growth. The soluble starch of carbon source was the best, the sorbose is the worst. The yeast extract of nitrogen source was the best for mycelial growth.2. The transfer of culture method by cutting mycelium was used to study the suitable conditions for produce conidia of Alternaria solani. The results showed that Alternaria solani for growing on oatmeal agar medium transfer to corn agar medium had the maximum spore quantity. The temperature of 25℃, pH 7～8 were favorable to produce conidia.The suitable light and UV had promotion for produce conidia.3. The hanging drop method was studied in order to make definite conidia germination conditions. The results showed that the conidia began to germinate in water in one hour at 30℃and germination rate of 98.4% in 8 hours. Temperature of 30℃, relative humidity above 85% and pH 6～10 were favorable to their germination. UV and Light had inhibition for conidial germination. The Gly, Ala and NH4NO3 of nitrogen sources had inhibition for conidial germination. Most of the carbon source was conducive to conidia germination.4. The different host species collected from the main potato growing areas in Heilongjiang had sixty-eight strains of Alternaria solani. Using inoculating detached leaves determined the virulence for sixty-eight strains. The results showed that the different strains had the virulence differentiation for KeXin 12, the strains could be divided into there types of strong, moderate, weak. The nine strains were powerful virulent, twenty-eight strains were moderate virulent, thirty-one strain showed weak virulence. There were not found the avirulent strains. The strain for different regions had difference for the virulence differentiation. The strain for same regions had obviously the virulence differentiation.5. Through compare cultural characteristics for the different virulence strains, there were some differences for color and shape of colonies in different strains. The dry weight of mycelium for powerful virulent strains were more in liquid medium, the toxin-producing capacity was strong. The dry weight of mycelium for powerful virulent strains were small in liquid medium, the toxin-producing capacity was weak.