Serotypic variation in turnip mosaic virus

A panel of 30 monoclonal antibodies (MAbs) was produced against four isolat es of turnip mosaic virus (TuMV). The panel was tested in plate-trapped ant igen ELISA tests against 41 TuMV isolates (with different host and geograph ical origins and of differing pathotypes). The antibodies were also tested against four other potyviruses (bean common mosaic virus, bean common mosai c necrosis virus, lettuce mosaic virus and zucchini yellow mosaic virus). T he reactions were assessed quantitatively (using multivariate analysis) and qualitatively (using the standard deviation obtained against healthy leaf material). The MAbs recognized 16-17 TuMV IV epitopes that were not present in the other potyviruses and a further two potyvirus epitopes. The isolate s were grouped into three serotypes. Only one isolate did not fit this grou ping. The classification of seven isolates in coat protein amino acid seque nce homology groups correlated with serotypes. There was no correlation bet ween serotype and pathotype, or between reactions to individual MAbs and si ngle lines. There was therefore no evidence that the epitopes recognized by the MAbs are elicitors for the resistance genes present in the Brassica na pus lines. However, the sensitivity and specificity of the MAbs will be use ful for both routine detection of TuMV and fundamental studies on plant-vir us interactions.