Successful interspecific hybridization between Cucumis sativus L. and C. hystrix Chakr

Abstract

Interspecific F1 hybrids were obtained from a cross between Cucumis sativus L. (2n = 2x = 14) and C. hystrix Chakr. (2n = 2x = 24). Controlled crossing resulted in fruit containing embryos which were excised and rescued on a Murashige and Skoog solid medium. A total of 59 vigorous plants were obtained from a fruit containing 159 embryos (37.3% regeneration rate). Hybrid plants were morphologically uniform. The multiple branching habit, densely brown hairs (especially on corolla and pistil), orange-yellow collora, and ovate fruit of F1 hybrid plants were similar to that of the C. hystrix paternal parent. While appearance of the first pistillate flower was more similar to that of C. sativus maternal parent than to C. hystrix, staminate flower appearance was mid-parent in occurence. The diameter and internode length of stem, shape and size of leaves and flowers were intermediate when compared to the parents. An elongated green, trilobate style/stigma which was not apparent in either parent was observed in staminate flowers of F1 plants. Similarly, the style/stigma of pistillate flower of F1 plants were longger when compared to their parents. The brown pubescence observed on pistillate flowers of the F1 and C. hystrix was not observed on the C. sativus parent. The somatic chromosome number of F1 plants was 19. Two morphologically distinct groups of chromosomes were observed in the F1 hybrid; 7 relatively large chromosomes characteristic of C. sativus, and 12 smaller chromosomes characteristic of C. hystrix. Analysis of malate dehydrogenase isozyme banding patterns provided additional comfirmation of hybridity. Reciprocal crossing of F1 plants to either parent and self-crossing indicated that the hybrids were male and female sterile.