A PCR-Based Assay for Wheat Soilborne Mosaic Virus in Hard Red Winter Wheat. R. E. Pennington, Research Associate, Department of Plant Pathology, Oklahoma State University, Stillwater 74078. J. L. Sherwood, and R. M. Hunger. Professor, and Professor, Department of Plant Pathology, Oklahoma State University, Stillwater 74078. Plant Dis. 77:1202-1205. Accepted for publication 26 May 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-1202.

A reverse transcription (RT)–polymerase chain reaction (PCR)–based assay that allows individual detection of RNA1 and RNA2 of wheat soilborne mosaic virus (WSBMV) was developed and utilized in conjunction with ELISA to detect WSBMV in Triticum aestivum. Resistant cultivars Newton and Hawk and susceptible cultivars Vona and Sage were planted 30 September 1991 in a field with a history of severe wheat soilborne mosaic. In ELISA, WSBMV was detected only rarely in root samples from either susceptible or resistant cultivars taken on 16 October or 2 November but in nearly all root samples taken on or after 4 December. RNA2 was detected in all ELISA-positive root samples and in most ELISA-negative root samples from either susceptible or resistant cultivars. Thus, RNA2 could be found in root samples of susceptible or resistant cultivars up to 7 wk before virus could be detected by ELISA. RNA1 was detected in most samples in which RNA2 was detected but was detected only rarely in samples in which RNA2 was not detected. In ELISA and/or RT-PCR, WSBMV was detected in most foliar samples from susceptible cultivars taken on or after 4 December. In ELISA and/or RT-PCR of foliar samples from resistant cultivars, however, detection of WSBMV was limited until the 1 March sampling. These results support the use of ELISA for evaluating cultivars for resistance to WSBMV and support the hypothesis that resistance is expressed as an inhibition of virus movement. The results do not support the possibility that resistance is expressed differentially against the two WSBMV RNAs.