Analysis On The Loss Of Disease Resistance Of Soybean Varieties To Gray Leaf Spot In Heilongjiang Province

The distribution and damage of gray speck of soybean had been researched meanwhile the pathogenic variation of Cercospora sojina Hara had been studied in the acquisition of the sample range and the loss of the resistance of the main varieties had been analyzed in this paper. The main results and conclusions were as follows:1 Based on the research data from 2013 to 2014, it was concerned that the occurrence of gray speck of soybean had a close relationship with the varieties of soybean, the amount of bacteria and the climate conditions. Soybean varieties of different mature period and type, different climate conditions, and different cultivating ways lead to a different damage. The distribution and damage of gray speck of soybean in the main soybean producing areas in Heilongjiang province were confirmed.2 The results of the determination of bacteria pathogenicity differentiation(pd) showed that there were 7 types of pd among the 55 strain samples in the eastern part of Heilongjiang province, that was 1,2,5,6,7,8,10;there were 8 types of pd among the 30 strain samples in the central part of Heilongjiang province, that was 1,2,3,4,6,7,9,10; there were 7 types of pd among the 32 strain samples in western part of Heilongjiang province, that was 1,2,4,5,6,7,10; there were 5 types of pd among the 12 strain samples in the southern part of Heilongjiang province, that was 1,4,6,7,10.3 The occurrence of high virulent strains and the rising of pathogenic frequency caused the loss of resistance of the main soybean varieties.The followings were the determination results:there were 35 varieties expressed resistance to Strain 1, accounted for 27.1% and 64 varieties expressed mid-resistance, accounted for 49.6%. To Strain 6, there were no resistant varieties and 41 varietie’s expressed mid-resistance, accounted for 31.8%. To Strain 7, there were 14 varieties expressed resistance, accounted for 10.9%; there were 56 varieties expressed mid-resistance, accounted for 42.6%. To Strain 10, there were no resistance varieties; there were 42 varieties expressed mid-resistance, accounted for 32.6%.