SCREENING MELON (CUCUMIS-MELO) FOR RESISTANCE TO GUMMY STEM BLIGHT INTHE GREENHOUSE AND FIELD

Greenhouse and field evaluations of melon (Cucumis melo L.) for resist ance to gummy stem blight, caused by the fungus Didymella bryoniae (Au ersw.) Rehm, were conducted on 798 U.S. Dept. of Agriculture Plant Int roduction (PI) accessions and 24 related Cucumis species. Plants were inoculated at the three to four true-leaf stage with a virulent isolat e of D. bryoniae collected from Onondaga County, N.Y., and disease ind ices were calculated based on foliar and stem symptoms. In greenhouse screens, 43 C. melo accessions showed a high level of resistance. Resu lts were consistent between the optimized greenhouse screening procedu re described and inoculated replicated field tests, Of these accession s, a Chinese group, PIs 157076, 157080, 157081, 157082, 157084; anothe r group from Zimbabwe, PIs 482393, 482398, 482399, 482402, 482403, 482 408; and some others from different origins, PI255478 (Korea) and PI 5 11890 (Mexico), showed high levels of resistance, at least equal to th at in PI 140471, the leading source of resistance to date.