Chromosome mapping of four novel mutants in bread wheat (Triticum aestivum L.)

Abstract

Induced mutants constitute an important resource for mapping and cloning of genes for specific traits. Five loci underlying four induced mutants in wheat were mapped using phenotypic data and simple sequence repeat (SSR) genotyping data collected on F2 and F3 populations. The four mutant traits included the following: (1) axillary branching, (2) early leaf senescence, (3) reduced plant height and (4) reduced number of nodes. The ‘axillary branching’ locus (Axb) was mapped near Xcfd152 at a distance of 7.5 cM on chromosome 3DS. The ‘early leaf senescence’ gene (els) was mapped on 2DL at a distance of 28.6 cM from the nearest marker Xgwm539. A wheat expressed sequence tag (EST) TaSAG1 representing a candidate for els gene for early leaf senescence was also identified. The ‘reduced plant height’ locus was mapped on chromosome 2BL close to Xwmc361, which is tightly linked with Xwmc317 associated with a ‘GA-responsive dwarfing gene’ Rht4; hence, the ‘dwarf mutant-3’ used in the present study may be a phenotypic manifestation of an another allele of the gene Rht4. The ‘reduced number of node’ mutant was mapped on two loci (rnd1 and rnd2) on chromosomes 2DS and 5AL. The marker locus Xgwm261-2D linked with rnd1 was earlier reported to be closely associated with Rht8 gene, suggesting that rnd1 may perhaps represent a mutation in Rht8 gene; the second locus rnd2 on 5AL represents a novel gene. These results may prove useful in explaining the genetics of four mutant traits and may later also facilitate cloning the genes for these traits.