Infection of gramineous species by Barley Yellow Dwarf Viruses in California

Abstract

Barley yellow dwarf viruses (BYDVs) continue to cause losses California cereal production. In some parts of the USA, native grasses have been implicated as reservoirs of BYDVs. This study examines the potential of native and irrigated pasture grasses as sources of BYDV inoculum in California. Theffects of both natural and natural plus supplemental inoculum were examined in field trials over two growing seasons using a completely randomized design. Results were assessed by enzyme-linked immunosorbent assay (ELISA) and verified with controlled greenhouse vector transmission trials. Thirty-seven of 56 species of cool-season grasses were infected by either PAV, MAV, or RPV isolates of the BYDVs. Of the BYDV-infected grasses, only 38% displayed symptoms typically seen in infected oat (Avena sativa L.) and barley (Hordeum vulgare L.), while the others were asymptomatic. None of the plants from seven species of Leymus, nor plants from the majority of Elymus and Elytrigia species, had detectable BYDV infections, even though they supported aphid vector populations. A survey of common grasses from irrigated pastures showed that plants from 6 of 10 species were infected by either the PAV, MAV, or RPV isolates of BYDVs. The incidence of MAV, PAV, and RPV BYDVs were roughly equivalent for the cool-season grasses, but were highly skewed toward PAV in the irrigated pasture survey. Both cool-season and irrigated warm-season pasture grasses have the potential to serve as BYDV reservoirs in California.