Plant Genome III Conference Plant Genome III Conference
Because it provides critical quality characteristics required in wheats exported to Asia, club wheat is a vital component of US western white wheat. Previously only one gene had been described as conferring the club head shape. The lack of variation for this trait has led us to search for additional compactum genes in wheat and its relatives. Crossing involving ploidy levels diploid, tetraploid, pentaploid and hexaploid have been made. Aneuploid stocks of the hexaploid Chinese Spring, tetraploid Langdon and extracted AB genomes from the common wheats Chinese Spring, Thatcher- and Canthatch were also used. Analysis of the hexaploid wheat AB genomes was carried out using the club wheats Moro, Wilbur and Union. In addition tetraploid club wheat Harlan-JR35 and the compact tetraploid species Triticum pyramidale were used to determine epistatic effects. The ratio obtained in the F2 derived from a cross between these parents was 9-7 (lax:dub) indicating the presence of two previously undescribed recessive genes for head type. Segregation ratios for F-2 populations derived from hybridizations between HarlanJR 35, T. pyramidale, Langdon, Maroccas (a compact durum) and TetraCS (Chinese Spring AB Mme) will be presented, These ratios were ascertained using both a visual scoring system and a quantitative measure of the spike density. The locations of the new compactum genes were determined using Langdon D-genome substitution lines: HarlanJR 35 has a compactum gene on chromosome 2B and T. pyramidale has one on chromosome 2A. These genes as well as the 2D Wm have been tagged using molecular markers. Genetic distances were calculated by RFLP analysis of the recombinant populations. Cytological analysis was carried out on mitotic and meiotic cells of the tetraploid lines and their Fl's. The discovery of the location, determination of gene action, and transfer of these two new compactum genes is allowing for more detailed manipulations of this important trait.