Population Dynamics and Infection of Cereal Cyst Nematode (Heterodera avenae) in Wheat in Beijing

Cereal cyst nematode, Heterodera avenae,is recognized as a highly destructive pathogen in wheat, causing serious yield and economic losses in China. During the wheat growing season of 2011-2012, population dynamics of second-stage juveniles (J2s) and pathogenicity of H. avenae were studied under natural field conditions in Beijing, China. Results indicated that the J2 population was bimodal during the wheat growing season. The first small peak of J2s appeared in late November with a maximum of 105 J2s/100 mL of soil. The main peak occurred in the following spring, from late March to early April, with a maximum of 295 J2s/100 mL of soil. The J2s hatched in the autumn were able to infect wheat roots and overwinter inside root system. However, J2s hatched in the spring season caused more severe infection with 230 juveniles/plant in the middle of April. Although the infection occurred twice in one growing season of wheat, only one cohort of adults were developed, resulted in an average of 287 females/plant in the middle of May. To determine the source of infective J2s in the autumn, in vitro and in vivo experiments were conducted to investigate the hatching and infection potential of newly produced cysts. The results showed that cysts incubated at 4℃ for 100 days produced more J2s than that of 50 d (P0.05). There were no J2s hatched from the cysts kept at room temperature for 50 d and 100 d. Moreover, cysts pretreated at 4℃ could cause infection of wheat roots during winter, while cysts kept at room temperature failed to induce any infection. It is confirmed that cold temperature is necessary for the hatching of J2s from cysts isolated in Beijing. Root infection by H. avenae in the autumn was due to the residual cysts remained in soil for two or more years. These findings would help us to understand the biology and ecology of H. avenae.