Gal-On, A., Dept. of Viroloev, Agricultural Research Organization, P.O.Box 6, Bet-Dagan, 50250, Israel
Wolf, D., Dept. of Plant Genetics, Agricultural Research Organization, P.O.Box 6, Bet-Dagan, 50250, Israel
Pilowsky, M., Dept. of Plant Genetics, Agricultural Research Organization, P.O.Box 6, Bet-Dagan, 50250, Israel
Zelcer, A.

Cucumber mosaic virus (CMV) epidemics occur worldwide in tomato fields, resulting in severe yield losses. Presently, no resistant commercial cultivars are available, since reponed sources of genetic resistance are unsatisfactory or genetically complex. We have recently described the generation of tomato lines which show immunity to CMV, following transformation with a truncated CMV replicase gene and subsequent screening of the Rl offsprings by mechanical inoculation (Gal-On et al, in press). A Fl hybrid was generated by crossing one of our most resistant lines with the appropriate complementary line. Field trials have indicated that deliberate inoculation with high titers of CMV resulted in ca. 50% reduction of yield in the non-transformedhybrid, while the transformed hybrid - hemizygous for the replicase gene - was unaffected and yielded normally.