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Chromosome Res. 2016 May;24(2):197-216. doi: 10.1007/s10577-015-9515-3. Epub 2016 Jan 12.

Highly distinct chromosomal structures in cowpea (Vigna unguiculata), as revealed by molecular cytogenetic analysis.

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Center for Applied Genetic Technologies, University of Georgia, 111 Riverbend Road, Athens, GA, 30602, USA.
Department of Biology, University of Pennsylvania, Philadelphia, 19104, PA, USA.
Department of Agronomy, Purdue University, 170 S. University Street, West Lafayette, IN, USA.
Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, CA, 90095, USA.
Department of Botany, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada.
Center for Applied Genetic Technologies, University of Georgia, 111 Riverbend Road, Athens, GA, 30602, USA.


Cowpea (Vigna unguiculata (L.) Walp) is an important legume, particularly in developing countries. However, little is known about its genome or chromosome structure. We used molecular cytogenetics to characterize the structure of pachytene chromosomes to advance our knowledge of chromosome and genome organization of cowpea. Our data showed that cowpea has highly distinct chromosomal structures that are cytologically visible as brightly DAPI-stained heterochromatic regions. Analysis of the repetitive fraction of the cowpea genome present at centromeric and pericentromeric regions confirmed that two retrotransposons are major components of pericentromeric regions and that a 455-bp tandem repeat is found at seven out of 11 centromere pairs in cowpea. These repeats likely evolved after the divergence of cowpea from common bean and form chromosomal structure unique to cowpea. The integration of cowpea genetic and physical chromosome maps reveals potential regions of suppressed recombination due to condensed heterochromatin and a lack of pairing in a few chromosomal termini. This study provides fundamental knowledge on cowpea chromosome structure and molecular cytogenetics tools for further chromosome studies.


Centromere; Molecular cytogenetics; Retrotransposon; Vigna unguiculata

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