Soybean cyst nematode(SCN Heterodera glycines Ichinohe) is one of the most important nationwide soybean pests in China.Density of SCN in 26 areas of Liaoning Province during 2006~2008 was determined for clarifying the distribution of SCN.The results showed that Heterodera glycines was found in88%areas,and the number of cyst per 100 g soil was more than 10 in 73%areas.The cyst density of Kangping was the biggest,up to 54.33,but the cyst density of Kaiyuan,Donggang and Huanren was 0,most areas were between 20 to 55.

Forty-two populations of Heterodera glycines were isolated from 22 counties in 14 cities in Liaoning province,China.According to the procedure of Golden et al,five differentials,Lee,Pickett,Peking,PI88788 and PI90763 were used to identify the races in 2007-2008.A map of race distribution was constructed according to the data from this experiment and literature cited.The results showed that a total of 14 samples could be divided into three races,including race 1,race 3 described previously and race 6,which first discovered in Liaoning province.Among them,race 1 was in Tieling;race 3 was found in Dalian,Panjin,Jinzhou,Benxi,Huludao,Fuxin,Anshan,Dongling District,Liaoyang,Dandong and Fushun,and race 6 in Chaoyang and Yingkou.However,race 3 distributed widely and was still principal race in Liaoning.