Interspecific cross between cucurbita pepo L. and Cucurbita martinezii through in vitro embryo culture

Summary

Ten plants were obtained following culture of one hundred interspecific embryos derived from the cross between the wild species Cucurbita martinezii Bailey as a male and the cultivated Cucurbita pepo L., as a female parent. Immature embryos were septically (cultured) on Murashige and Skoog medium with 0.01 mg/l IAA and 0.1 mg/l KIN, which proved to be the best for squash embryo culture. Interspecific plants showed intermediate morphological characters between parents leaves and flowers. Moreover, biochemical analysis of the peroxidase isozymes as electrophoretic banding patterns showed the same intermediate trend with hybrid plants showing the majority of cultivated and wild parent bands. On the other hand, no great differences were detected between the hybrid and its parents for albumin banding patterns. Cytological studies of mitotic and meiotic chromosomes showed that hybrid root tips had the same number of chromosomes as the parents (2n=40). However mitotic chromosome karyotypes represent two main distinct groups in morphology, one from each parental species. Meiotic chromosomes of hybrids showed a high level of irregular univalent formation and low level of bivalents and chiasmata formation, supporting the conclusion that the genomes of the two species are quite different. Regarding powdery mildew and cucumber mosaic virus infectivity, both the hybrid plants and the wild parent proved to be resistant to both diseases, whereas, the cultivated parent proved to be highly susceptible.