title: Identification of a major QTL controlling the content of B-type starch granules in Aegilops.
abstract: Starch within the endosperm of most species of the Triticeae has a unique bimodal granule morphology comprising large lenticular A-type granules and smaller near-spherical B-type granules. However, a few wild wheat species (Aegilops) are known to lack B-granules. Ae. peregrina and a synthetic tetraploid Aegilops with the same genome composition (SU) were found to differ in B-granule number. The synthetic tetraploid had normal A- and B-type starch granules whilst Ae. peregrina had only A-granules because the B-granules failed to initiate. A population segregating for B-granule number was generated by crossing these two accessions and was used to study the genetic basis of B-granule initiation. A combination of Bulked Segregant Analysis and QTL mapping identified a major QTL located on the short arm of chromosome 4S that accounted for 44.4% of the phenotypic variation. The lack of B-granules in polyploid Aegilops with diverse genomes suggests that the B-granule locus has been lost several times independently during the evolution of the Triticeae. It is proposed that the B-granule locus is susceptible to silencing during polyploidization and a model is presented to explain the observed data based on the assumption that the initiation of B-granules is controlled by a single major locus per haploid genome.
authors.affiliation: John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: Howard
authors.forename: Nur Ardiyana
authors.initials: NA
authors.lastname: Rejab
authors.forename: Simon
authors.initials: S
authors.lastname: Griffiths
authors.forename: Fiona
authors.initials: F
authors.lastname: Leigh
authors.forename: Michelle
authors.initials: M
authors.lastname: Leverington-Waite
authors.forename: James
authors.initials: J
authors.lastname: Simmonds
authors.forename: Cristobal
authors.initials: C
authors.lastname: Uauy
authors.forename: Kay
authors.initials: K
authors.lastname: Trafford
mesh_terms: D032461:Chromosomes, Plant; D006109:Poaceae / Q000235:genetics* / Q000378:metabolism; D040641:Quantitative Trait Loci; D013213:Starch / Q000378:metabolism*; D057891:Tetraploidy
chemical_list: D013213:Starch