Price, H. James , Hodnett, George L. , Burson, Byron L. , Kuhlman, Leslie C. , Stelly, David M. , Rooney, William L. .
Reproductive isolation and interspecific hybridization in the genus Sorghum.
The genus Sorghum has 25 species forming two lineages: one with 2n = 10 relatively large genome species and polyploid relatives (subgenera Para-sorghum and Stiposorghum); the other with 2n = 20 and 2n = 40 species with smaller genomes (Subgenera Eu-sorghum, Chaetosorghum, Heterosorghum). Strong reproductive isolation barriers have prevented successful hybridization of S. bicolor with any Sorghum species classified in subgenera other than Eu-sorghum. Pollen-pistil incompatibility is the primary reason why hybrids can not be produced. There is a reduction of alien pollen germination and tube growth in sorghum stigmas. This incompatibility mechanism was overcome by using a S. bicolor genotype that allows growth of pollen tubes of alien Sorghum species. Hybrids have been recovered after dusting the stigmas of S. bicolor with pollen from diverse species such as S. angustum,S. nitidum and S. macrospermum. Analysis of chromosome pairing in the S. bicolor x S. macrospermum hybrid showed homology between the two species. This, along with additional cytogenetic, morphological, and DNA sequence comparisons support the hypothesis that S. bicolor is phylogenetically closer to S. macrospermum than it is to species of the subgenera Para-sorghum and Stiposorghum. Research supported by TAES, USDA Sorghum Germplasm Committee, and CSREES NRI Competitive Grant 2004-35300-14686.
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1 - Texas A&M University, Department of Soil and Crop Sciences, Mail Stop 2474, College Station, Texas, 77843-2474, USA
2 - USDA-ARS, Crop Germplasm Research Unit, 430 Heep Center, Texas A&M University, College Station, Texas, 77843
Presentation Type: Oral Paper
Date: Monday, August 15th, 2005
Time: 1:15 PM