Biological and molecular characterization of a highly divergent johnsongrass mosaic virus isolate from Pennisetum purpureum
When 23 accessions of pearl millet growing in 1990 at Gatton, south-eastern Queensland, were examined for virus infection, all accessions had plants with mosaic symptoms. Using sorghum differential test plants, it was shown that Johnsongrass mosaic virus (JGMV) was commonly associated, but one isolate of the sabi grass strain of sugarcane mosaic virus (SCMV) was also obtained. In glasshouse tests where 15 accessions of pearl millet were each inoculated with JGMV and the three Australian strains of SCMV 17 days after sowing, all 15 were infected by JGMV and the sabi grass strain of SCMV. However, only two pearl millet accessions were infected by the Queensland blue couch grass strain of SCMV and 14 with the sugarcane strain of SCMV. JGMV caused an average of 60% decrease in dry matter yield 83 days after sowing, whereas strains of SCMV caused less stunting.