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Genotype Dependent Interspecific Hybridization of Sorghum bicolor

Price, H. James, Hodnett, George L., Burson, Byron L., Dillon, Sally L., Stelly, David M., Rooney, William L.
Crop science 2006 v.46 no.6 pp. 2617
Sorghum bicolor, grain sorghum, wild relatives, plant genetic resources, wide hybridization, interspecific hybridization, plant breeding, alleles, recessive genes, pollen, gynoecium, cytoplasmic male sterility, homozygosity, pollen germination, pollen tubes, ovules, embryo (plant), embryo culture
Wild Australian species are a tertiary gene pool to grain sorghum [ (L.) Moench], and they are of interest to breeders because of their resistance to important insects and pathogens. However, strong reproductive barriers have prevented hybridization between and these wild species. The purpose of this study was to determine if the recessive allele (dominant allele) would reduce or eliminate the pollen–pistil incompatibilities that prevent hybridization between and divergent species. Cytoplasmic male-sterile plants, homozygous for the allele, were pollinated with three divergent species, Blake, (Vahl) Pers., and Garber. The pollen of these three wild species readily germinated and the pollen tubes grew to the base of the ovary within 2 h after pollination. Hybrid embryos were detected in the florets 13 to 20 d post-pollination. × and × hybrids were obtained using embryo rescue followed by in vitro culture techniques and hybrids between and were obtained by simply germinating the hybrid seed. These hybrids were confirmed by their morphological and cytological traits. These findings clearly demonstrate that the recessive allele circumvents pollen–pistil incompatibilities in the genus and permits hybrids to be made between and species of the tertiary gene pool.