Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/1996
Publication Date: N/A
Citation: Interpretive Summary: Genetic variation of wheat streak mosaic virus, which causes a destructive disease in wheat, was quantified for the first time. Virus isolates from individual plants were fingerprinted by employing a technique called the polymerase chain reaction. Over a two-year study of five Nebraska counties we found 32 different types of wheat streak mosaic virus. However, three types occurred most frequently. Virus isolates collected from within a single field were as variable as virus collected from different counties. This was quite unexpected but likely means that the virus and its mite vector are introduced into wheat fields from numerous sources. The make up of virus populations in 1994 was different from that in 1995 across all Nebraska counties. This suggests that virus and mite become dispersed throughout the region each year. Many unanswered questions about the spread of wheat streak mosaic virus can now be approached using virus isolates with distinctive fingerprints.
Technical Abstract: A reverse transcriptase-polymerase chain reaction (RT-PCR) assay was developed to amplify cDNA from the coat protein cistron and 3'-noncoding region of the genome of wheat streak mosaic virus (WSMV). AluI restriction fragment length polymorphisms (RFLPs) were found among RT-PCR p ts of four spatially or temporally distinct WSMV isolates. RT-RCR and RFLP sis was then applied to examine intra- and inter-field genetic variation in natural WSMV populations in 1994 and 1995. A total of 32 distinct RFLP types were found in five Nebraska counties but most isolates could be grouped into three predominant genotypes. Chi square analysis of the degree of genetic heterogeneity of isolates within fields, among fields each county, and among counties indicated that there was as much variation within fields as among counties. There was, however a significant difference (P=0.001) in the frequencies of WSMV RFLP types between 1994 and 1995. Results of this study suggest that there are three main and many minor lineages of WSMV co-circulating in the region. Isolates with distinctive RFLP patterns should facilitate future studies of WSMV dispersal.