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Systematics Section / ASPT

Kellogg, Caroline D. [2], Doyle, Jeff J. [1], Kresovich, Stephen [3].

Understanding genome origins and evolution of a complex polyploid, Sorghum halepense (Poaceae).

One of the most challenging problems in systematics is understanding the relationships between closely related species, especially those that have been subject to processes such as polyploidy, hybridization, and introgression. This research investigates the effects of these processes on the relationships among species of Sorghum sect. Sorghum (Poaceae). Sorghum sect. Sorghum includes cultivated sorghum [Sorghum bicolor (L.) Moench (2n = 2x = 20)] and johnsongrass [Sorghum halepense (L.) Pers. (2n = 4x = 40)], one of the world's most noxious weeds. We have constructed haplotype networks from several unlinked nuclear loci for individuals of the S. bicolor/S. halepense species complex. These haplotype networks are used to infer the origins of the genomes of the polyploid S. halepense. Complex patterns are seen in the haplotype networks for individual loci, as well as in comparisons between loci. Data from numerous individuals and loci highlight problems of incongruence, which are not unexpected due to the many factors influencing the evolutionary history of these species. Sorghum halepense is known to exhibit both tetrasomic and disomic inheritance, which may provide an explanation for the absence of alleles from one progenitor at some loci. Independent assortment and gene flow between the diploid progenitors and polyploids also may be contributing to the differing patterns seen when comparing results from multiple loci. Tetrasomic inheritance can allow for recombination or gene conversion between progenitor alleles, creating complex patterns in the haplotype network for a single locus.

1 - Cornell University, L.H. Bailey Hortorium, Department of Plant Biology, Ithaca, New York, 14853, U.S.A.
2 - Cornell University, L.H. Bailey Hortorium and Institute for Genomic Diversity, Ithaca, New York, 14853, U.S.A.
3 - Cornell University, Institute for Genomic Diversity, Department of Plant Breeding, Ithaca, New York, 14853, U.S.A.

polyploid origin
haplotype network
gene flow
tetrasomic inheritance.

Presentation Type: Poster
Session: 32-87
Location: Special Event Center (Cliff Lodge)
Date: Tuesday, August 3rd, 2004
Time: 12:30 PM
Abstract ID:770

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