Genetic Variation of Soybean Cyst Nematode Races in Anda Area of Heilongjiang Province

Soybean cyst nematodes (SCN) is one of most important diseases to cause severe yield loss on soybean each year in the world.Heilongjiang Province is one of the major production areas of soybean in China.Reduced or lost resistance to major SCN race 3 for some resistant variety was observed in the field.Yet it was not clear how SCN races changed in the field.Currently,the identification method of SCN races by Riggs and Schmitt has its limitation.The comparison of resistance by using egg production from cysts might be another important indicator.In this study,two soil samples were collected from the field where the SCN races were changed with initial identification in the field.SCN race 4 collected from Shandong was as control.Single cyst from each soil samples was cultured and reproduced in susceptible soybean.Then differential hosts were inoculated and numbers of cysts in the soil and on the root were investigated 35-40 days after inoculation.Eggs were collected from these cysts.Two samples from Anda District were identified as SCN race 4 based on the female index,which was same as SCN race 4 from Shandong.However,dramatic variation in the number of eggs per plant was identified between SCN race 4 from Shandong and the two samples from Anda.Yet both the field test and greenhouse test consistently showed variation of SCN races from race 3.The greenhouse test suggested the two samples might be race 4,but with virulence difference compared with race 4 from Shandong based on the number of eggs per plant.