Soybean Law On Prevention And Control Of Gray Leaf Spot

Results of plot showed that different levels of Cercospora sojina causes disease had different effect on the yield of soybean. Greater the disease severity was, more the yield lost .Leaf, stem and pod all could produce spores under natural depoist treatments, while spores could be produced more in stem and pod. The amounts that every part could produce were more than those of the corresponding parts buried.Happiness of this disease had close relation with soybean varieties. Major soybean promoted races showed resistant-susceptible to Cercospora sojina, while a little races showed high resistance to Cercospora sojina in the place where this disease severity was heavy.10 races were identified by using a set of self–use differential hosts. Among them, the frequency of race 1 was highest and it was most widely distributed, followed by race 7, race 10, third place; others in turn 2, 3, 9, 4, 8, 6 and 11.Resistance of major promoted races and promising lines were identified by way of virulence frequency statistics and calculated analysis. Some Cercospora sojina isolates showed high virulence frequency to major Heilongjiang promoted soybean races. Two soybean races had low virulence frequency, seven races with moderate virulence frequency, 14 races with high virulence frequency.Result of 648 copies identification showed 55copies with high resistance, 210 with moderate resistance and 303copies with susceptiblity. More than half of major promoted cultivars showed certain resistance to race 1, 28 copies had medium resistance level. Race 1 emerged with highest frequency from races emerging frequency, it was dominant specie.Suinong 8 had highest disease severity in contiguous planting of susceptible cultivars system, followed by No. 4. In resistant and susceptible cultivars intercropping system, disease index of each susceptible cultivar was lower than corresponding control, the decline of Hefeng 25,s disease index was most obvious. Whether in contiguous planting of susceptible cultivars system or in contiguous planting of susceptible cultivars system, disease index of Hefeng 25 was lower than the other two susceptible varieties, it was a high resistant variety close to be a susceptible variety.