Compactum (C) -
Club wheat (Triticum aestivum ssp. compactum) carries the
dominant form of the compactum (C) gene resulting in a compact spike
relative to spikes of common wheat (T. aestivum ssp. aestivum).
The C locus, with its effect on spike compactness
and rachilla morphology, also has an effect on rachis toughness. Thus, its
effect on a trait important to domestication may explain its presence in cultivated
hexaploid forms. Toward the eventual isolation and characterization of this
gene, we undertook a project to locate C on genetic linkage maps of
chromosome 2D (Johnson et al. 2007). The C locus
was completely linked to markers placed in two different bins flanking the
centromere. We are therefore unable to map C to a precise bin or chromosome
arm. A cytogenetically-based study performed by
Rao (1972: Wheat
Information Service 35:9) placed C on the long arm of chromosome 2D.
Thus, we suspect that C is located in a chromosomal segment near the
centromere in the long arm of chromosome 2D. Due to C’s
proximity to the centromere, the map-based isolation of this
gene will be challenging
because proximal
segments of chromosomes are characterized by large physical distance with greatly
reduced levels of recombination.
Publications
Johnson, E., J.M. Leonard, R.S. Zemetra, and O. Riera-Lizarazu. 2007.Mapping the compactum (C) locus in wheat. In: Abstracts of Plant & Animal Genome XV, January 13-17, San Diego, CA.