ATTEMPTS TO OVERCOME THE BARRIER OF INTERSPECIFIC HYBRIDIZATION BETWEEN CUCUMIS MELO AND C. METULIFERUS

Abstract

The crossability ofCucumis meloandC. metuliferuswas studied in order to find ways to effect the cross between the two species. In cross-pollination withinC. melo, the pollen tubes entered the ovarian cavity within 24 h, and fertilization occurred within 48 h. Pollen germinated well after cross-pollination between the species, but pollen tubes grew slowly.C. metuliferuspollen tubes were arrested in the stigma or the upper style ofC. meloflowers.The influence of 100-, 150-, and 200-krad gamma radiation on in vitro germination, pollen tube growth ofC. meloandC. metuliferus, and on in vivo fertilization ofC. melowas studied. Pollen ofC. metuliferusappeared to be much less sensitive to gamma rays than that ofC. melo.Higher radiation doses were found to reduce fruit set ofC. melo.Irradiation of pollen ofC. meloalways resulted in “pseudo-fertilization”.We attempted to overcome the prefertilization crossing barrier betweenC. meloandC. metuliferusby using techniques of bud pollination, benzyladenine (BA) treatment, and irradiated mentor pollen. Ten lines ofC. meloand 6 accessions ofC. metuliferuswere used as female and male parents, respectively. The techniques of BA and bud pollination were ineffective. Numerous fruits with few embryos were obtained on some of theC. melolines after using the irradiated mentor pollen technique. Embryos, which were isolated at the age of 20–25 days and cultured on medium consisting of 1/3 Murashige and Skoog medium, were observed to provide normal development. All nine surviving plants were similar to the maternal parent and were not interspecific hybrids.