title: Molecular mapping of genes for Coleoptile growth in bread wheat (Triticum aestivum L.).
abstract: Successful plant establishment is critical to the development of high-yielding crops. Short coleoptiles can reduce seedling emergence particularly when seed is sown deep as occurs when moisture necessary for germination is deep in the subsoil. Detailed molecular maps for a range of wheat doubled-haploid populations (Cranbrook/Halberd, Sunco/Tasman, CD87/Katepwa and Kukri/Janz) were used to identify genomic regions affecting coleoptile characteristics length, cross-sectional area and degree of spiralling across contrasting soil temperatures. Genotypic variation was large and distributions of genotype means were approximately normal with evidence for transgressive segregation. Narrow-sense heritabilities were high for coleoptile length and cross-sectional area indicating a strong genetic basis for differences among progeny. In contrast, heritabilities for coleoptile spiralling were small. Molecular marker analyses identified a number of significant quantitative trait loci (QTL) for coleoptile growth. Many of the coleoptile growth QTL mapped directly to the Rht-B1 or Rht-D1 dwarfing gene loci conferring reduced cell size through insensitivity to endogenous gibberellins. Other QTL for coleoptile growth were identified throughout the genome. Epistatic interactions were small or non-existent, and there was little evidence for any QTL x temperature interaction. Gene effects at significant QTL were approximately one-half to one-quarter the size of effects at the Rht-B1 and Rht-D1 regions. However, selection at these QTL could together alter coleoptile length by up to 50 mm. In addition to Rht-B1b and Rht-D1b, genomic regions on chromosomes 2B, 2D, 4A, 5D and 6B were repeatable across two or more populations suggesting their potential value for use in breeding and marker-aided selection for greater coleoptile length and improved establishment.
authors.affiliation: CSIRO Plant Industry, GPO Box 1600, Canberra, ACT, 2601, Australia. Greg.Rebetzke@csiro.au
authors.forename: G J
authors.initials: GJ
authors.lastname: Rebetzke
authors.forename: M H
authors.initials: MH
authors.lastname: Ellis
authors.forename: D G
authors.initials: DG
authors.lastname: Bonnett
authors.forename: R A
authors.initials: RA
authors.lastname: Richards
mesh_terms: D001939:Bread; D002874:Chromosome Mapping; D032461:Chromosomes, Plant; D018548:Cotyledon / Q000235:genetics* / Q000378:metabolism*; D003433:Crosses, Genetic; D004843:Epistasis, Genetic; D017343:Genes, Plant; D005838:Genotype; D008954:Models, Biological; D008957:Models, Genetic; D040641:Quantitative Trait Loci; D013696:Temperature; D014908:Triticum / Q000235:genetics*