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TitleCrop-to-weed introgression has impacted allelic composition of johnsongrass populations with and without recent exposure to cultivated sorghum
AuthorsP. L. MORRELL, T. D. WILLIAMS-COPLIN, A. L. LATTU, J . E . BOWERS, J. M. CHANDLER
and A. H. PATERSON
Year2005
Taxonsorghum
PDFmec_2579.pdf
PublicationMolecular Ecology 14: 2143-2154
Journal_link
Publisher_note
Supplemental
AbstractSorghum halepense L. (johnsongrass) is one of the world's most noxious weeds, and a paradigm for the potential dangers of crop-weed
hybridization. Introduced into the southeastern United States about 200 years ago, S. halepense is a close relative of cultivated
sorghum ( Sorghum bicolor ). Both artificial crossing and experimental field studies have demonstrated the potential for S. halepense x
S. bicolor hybrid formation, but no prior study has addressed the long-term persistence of sorghum genes in johnsongrass populations.
We surveyed 283 loci (on all 10 sorghum linkage groups) to identify 77 alleles at 69 loci that are found in US sorghum cultivars but
are absent from a worldwide sampling of johnsongrass genotypes. These putatively cultivar-specific alleles were present in up to 32.3%
of individuals in johnsongrass populations adjacent to long-term sorghum production fields in Texas and Nebraska. Lower frequencies of
cultivar-specific alleles at smaller numbers of loci are found in johnsongrass populations from New Jersey and Georgia with no recent
exposure to cultivated sorghum, suggesting that introgressed sorghum alleles may be dispersed across long distances. The number of
cultivar-specific alleles and extensive multilocus patterns of cultivar-specific allelic composition observed at both linked and
unlinked loci in the johnsongrass populations, are inconsistent with alternatives to introgression such as convergence, or joint
retention of ancestral polymorphisms. Naturalized johnsongrass populations appear to provide a conduit by which transgenes from sorghum
could become widely disseminated.

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