Production of near-isogenic lines of common wheat for glaucousness and genetic basis of this trait clarified by their use

Duplication of the genes for both wax production (W loci) and inhibition (proposed symbol, Iw loci) on chromosomes 2B and 2D hindered clarification of the allelic and linkage relationships between these loci in wheat. The near-isogenic lines of three genotypes, w1w1 w2w2, W1W1 w2w2 and w1w1 W2W2, for wax production (all iw1iw1 iw2iw2 for wax inhibition) and two genotypes, Iw1Iw1 iw2 iw2 and iw1 iw1 Iw2Iw2, for wax inhibition (both W1W1 W2W2 for wax production) therefore were produced by ten backcrosses with Triticum aestivum cv. S615 (genotype W1W1 W2W2 iw1iw1 iw2iw2), or its equivalent w-S615 (w1w1 w2w2 iw1iw1 iw2iw2), as the recurrent parent. Segregation ratios between glaucous and non-glaucous plants in successive backcross generations or after selfing the backcrossed offspring indicated that all the wax-producing (W) and inhibiting (Iw) alleles were transmitted at equal frequencies to their respective recessive alleles, w and iw. Linkage analyses of W1, Iw1 and Ne2 (a gene for hybrid necrosis) on chromosome 2B and W2, Iw2 and C (a gene for compact ear) on chromosome 2D showed that the W1 and W2 loci respectively are located at sites different from the Iw1 and Iw2 loci. The presently accepted concept of multiple allelism for w, W and W-I (wax inhibition) therefore is invalid. Rather two allelic sets, w and W, and iw and Iw, both of which are duplicated on chromosomes 2B and 2D, must be postulated for the glaucousness of wheat. The first genetic maps showing their linkage relationships to the centromere and the Ne2 and C loci have been constructed.