LINKAGE ANALYSIS OF POTYVIRUS RESISTANCE ALLELES IN CUCUMBER

The cucumber (Cucumis sativus L.) line TMG-1 is resistant to at least four related potyviruses including zucchini yellow mosaic virus (ZYMV) , watermelon mosaic virus (WMV), and the watermelon strain of papaya r ingspot virus (PRSV-W). Resistance to ZYMV is due to a single recessiv e gene (zym), PRSV-W to a single-dominant gene (Prsv-2), and WMV to tw o separable factors. One WMV resistance factor (wmv-2) is expressed in the cotyledon and throughout the plant, The second, which results fro m an epistatic interaction between two genes (wmv-3, Wmv-4), is expres sed only in true leaves. We tested for linkage relationships between t hese virus resistance loci and an array of morphological, isozyme, and fungal disease resistance loci. Linkages were detected between resist ance to WMV and ZYMV, between the cotyledon-expressed resistance to WM V (wmv-2) and the F locus for gynoecious sex expression (linkage group I), and between resistances to PRSV-W (Prsv-2) and ZYMV (zym) and bit terfree cotyledon (bi; linkage group I). The proposed sequence and map distances on linkage group I are Prsv-2/zym-28 cM-bi-34 cM-F-33 cM-wm v-2.