Incidence of Viruses Infecting Winter Wheat in Alabama.

The most important viral diseases of wheat are caused by Barley yellow dwarf virus (BYDV, strains PAV and MAV) and Cereal yellow dwarf virus (CYDV, strain RPV). Starting in 2000, winter wheat crops growing in northern, central, and southern Alabama were evaluated for the occurrence of BYDV-PAV and CYDV-RPV. In addition to these viruses, samples were tested for the presence of Soilborne wheat mosaic virus (SBWMV), Wheat spindle streak mosaic virus (WSSMV), and Wheat streak mosaic virus (WSMV). BYDV-PAV and CYDV-RPV were found throughout the state, alone or as co-infections, in 14.6% of the samples collected in 2000 and 12.2% of samples in 2001. PAV was found at a lower incidence than RPV (4.3 and 9.9%, respectively) in 2000; however, in 2001, PAV was detected in 8.2% and RPV in 1.9% of the samples. There was less rainfall than the 30-year average during the 1999-2000 growing season, and this may have contributed to differences in the relative incidence of PAV and RPV between the 2 years. SBWMV, WSSMV, and WSMV also were detected in Alabama in 2, 7.8, and 5.4% of the samples collected in 2000, respectively, and in 9.6, 34.3, and 18.5% of the samples collected in 2001, respectively. This is the first report of WSMV in Alabama winter wheat.