Abstract: Greenbug Schizaphis graminum is an equally important pest of wheat in China as it is in the United States. The occurrence of greenbug biotypes is well-documented and ten biotypes (from A to J) have been identified in USA. However, the biotype study of greenbug in China is still very rare by now. The objectives of this study are:(1) to characterize the virulence of greenbug in Beijing area, and (2) to determine whether the Beijing biotype is different from the previously reported ones. As a set of standard differential hosts, major plant sources of greenbug resistance were evaluated against field collections of Beijing greenbug between 1996 and 1997, and seedling plant damage was rated on a 1 to 6 scale, where l=no damage, and 6=dead plant. The patterns of aphid-feeding damage on differential hosts were rated as: Wheat DS 28A (gb₁)=6, Amigo (Gb₂) =1, Largo (Gb₃) =2, CI17959 (Gb₄) =6, CI17882 (Gb₅) =3,GRS1201 (Gb₆)=3.5, Oats CI1580= 1, and Rye Insave= 1. Compared with damage patterns caused by any previously described biotypes, Beijing greenbug population is revealed clearly to be a new biotype, and is hereby designated as biotype CHN-1.

Key words: Schizaphis graminum, biotype, CHN-1, wheat, greenbug resistance