Evaluation of aphid transmission abilities and vector transmission phenotypes of barley yellow dwarf viruses in China

Barley yellow dwarf viruses (BYDVs) are economically important viruses that infect cereal crops worldwide, including wheat grown in China. These viruses include several members of the Luteoviridae and are transmitted only by aphids. In this study, BYDV isolates and their aphid vectors were collected from different regions of China and assayed. BYDV isolates from China were generally transmitted by more than one aphid species except for BYDV-RMV and a few BYDV-PAV, Seven vector transmission phenotypes (VTPs) were identified involving five serotypes; BYDV-GAV, BYDV-GPV and BYDV-PAV were predominant in China. Aphid clones differing in virus transmission abilities were occasionally observed for three laboratory-maintained species although they generally showed similar virus transmission profiles. Degenerate primers similar to Lu1 and Lu4 were designed to amplify coat protein gene fragments from all in the virus collection. Serotypes could be distinguished after cleavage of the resulting PCR products with HinfI. Sequence variations among Chinese BYDVs were also deduced from differences among their restriction patterns. To clarify this, intact coat protein genes of a few isolates were amplified with serotype-specific primers, cloned and sequenced. Similarity and genetic distance analyses confirmed that the three major Chinese BYDVs possess coat protein genes distinct from those of BYDV from other countries.