Compatibilidad genetica y flujo de genes entre Cucurbita moschata y C. argyrosperma

The relationship between C. moschata Duchense and C. argyrosperma Huber appears to be closer than that of the other species of Cucurbita. Cucurbita moschata (tropical pumpkin) is cultivated in the lowland, humid tropics. Cucurbita argyrosperma is cultivated in Central America for seed consumption. The two species are often sympatric in that region. The objective of this research was to study the potential for gene flow (introgression of genes of one species into the genome of another) and the degree of genetic compatibility between these species by studying progenies from various controlled pollinations, as well as from field plantings with open (uncontrolled) pollination. There was greater genetic incompatibility between various genotypes of C. argyrosperma and C. moschata when C. moschata was the maternal parent in crosses between the species. Nevertheless, gene flow of C. argyrosperma to C. moschata occurred in an indirect form when C. moschata was pollinated with the interspecific F1 progeny [C. moschata x (C. argyrosperma x C. moschata)]. This latter cross (C. moschata x F1) and its reciprocal (F1 x C. moschata) have the same nuclear but different cytoplasmic genomes. The cytoplasmic genome did have an effect on the length of the fruit. Rind lignification, flesh bitterness and growth habit have normal genetic segregation in interspecific crosses, suggesting a high degree of homology between the species, and each locus appeared to be independent (not linked). Under open pollinated field conditions genes of C. moschata were observed to move to C. argyrosperma when these two species grow simultaneously.