MELON RUGOSE MOSAIC-VIRUS - CHARACTERIZATION OF AN ISOLATE FROM SUDANAND SEED TRANSMISSION IN MELON

Melon rugose mosaic virus (MRMV) was isolated from snake cucumber (Cuc umis melo var. flexuosus) in the Kassala region of Sudan in 1993. The host range of the virus was mostly limited to cucurbits, where it indu ced severe mosaic and leaf deformations. Cytopathological studies reve aled severe chloroplast alterations, including vesicles at their perip hery and the tendency to aggregate, which are typical of tymovirus inf ections, providing further evidence that MRMV is a tentative member of the genus Tymovirus. In melon and snake cucumber, MRMV was found to b e seed transmitted at rates of 0.9 and 3.8%, respectively. Seed dissec tion experiments revealed that the virus could be detected in the seed coat, papery layer, and embryo. Seed disinfection treatments did not reduce seed transmission rates, which suggests an internal transmissio n. A preliminary screening for resistance in melon revealed some resis tance in two out of 367 accessions tested.