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- Author or Editor: Konstantinos Anagnostou x
We have studied the relationship of resistance to watermelon mosaic virus (WMV), zucchini yellow mosaic virus (ZYMV), papaya ringspot virus (PRSV), and powdery mildew (PM) in melon (Cucumis melo). We have confirmed monogenic dominant inheritance of these four resistances and report that PI414723-4S3, which was initially selected as a source of ZYMR, is also a source of dominant monogenic resistance to PRSV. Further, we observed departure from independent assortment for resistance to WMV and ZYMV in a study of 73 (UC Top Mark × PI414723-4S3) F3 families (χ2 = 39.87 significant at both 0.01 and 0.05 levels), indicating linkage between Wmv and Zym. The map distance between these resistance genes calculated from the number of recombinant families (RF% = 9.58) was 10.5 cM. Compari-sons among WMV, PM, ZYMV-PM, PRSV-PM, ZYMV-PRSV, and WMV-PRSV of 48 (TM × PI414723-4S3) F3 families, which were screened with all four pathogens, showed no consistent cosegregation.
Greenhouse and field evaluations of melon (Cucumis melo L.) for resistance to gummy stem blight, caused by the fungus Didymella bryoniae (Auersw.) Rehm, were conducted on 798 U.S. Dept. of Agriculture Plant Introduction (PI) accessions and 24 related Cucumis species. Plants were inoculated at the three to four true-leaf stage with a virulent isolate of D. bryoniae collected from Onondaga County, N.Y., and disease indices were calculated based on foliar and stem symptoms. In greenhouse screens, 43 C. melo accessions showed a high level of resistance. Results were consistent between the optimized greenhouse screening procedure described and inoculated replicated field tests. Of these accessions, a Chinese group, PIs 157076, 157080, 157081, 157082, 157084; another group from Zimbabwe, PIs 482393, 482398, 482399, 482402, 482403, 482408; and some others from different origins, PI 255478 (Korea) and PI 511890 (Mexico), showed high levels of resistance, at least equal to that in PI 140471, the leading source of resistance to date.