QTL Mapping For Starch Granule Size Distribution And Its Correlations With Starch Properties In Common Wheat

Starch is a crucial component determining the processing quality of wheat-based products. Wheatstarch generally contains A-type and B-type starch granules, having different effects on starch propertyand end-use quality. In the present study,265leading wheat cultivars and advanced lines, grown inAnyang, Henan province during2010-2011and2011-2012cropping seasons, were used to study thedistributions of A-type and B-type starch granules in cultivars (lines) and the correlations with pastingproperties and amylose content. The percentage volumes of A-type and B-type starch granules weredetermined using a laser diffraction particle size analyzer. Pasting properties and amylose content wereinvestigated with rapid visico analyser and amylose analyser. In addition,240recombinant inbred linesderived from PH82-2/Neixiang188cross were grown in Anyang, Henan province during2005-2006,2010-2011and2011-2012cropping seasons. A total of195SSR markers were used to construct geneticmaps of the population. QTL analysis for wheat starch granule size distribution was performed bycomposite interval mapping with the software QTL Cartographer v2.5. The main results obtained in thisstudy are summarized below.1. The genetic variation of starch granule size distribution and its correlations with starchproperties in common wheatSignificant differences for the percentage volumes of A-type and B-type starch granules wereobserved in leading cultivars and advanced lines. The percentage volumes of A-type and B-typegranules and A:B ratio ranged from70.7to90.4%,8.5to26.8%and2.76-10.63, respectively. Theirbroad-sense heritabilities were81.5%,81.0%and82.9%, respectively. Genotypes, years and theirinteraction showed significant variances.The percentage volumes of A-type and B-type starch granules and A:B ratio were significantlycorrelated with pasting temperature, peak viscosity and final viscosity, but they were not significantlycorrelated with other pasting properties. In detail, the percentage volume of A-type starch granules wassignificantly positively correlated with pasting temperature, peak viscosity and final viscosity, withcorrelation coefficients of0.33,0.25and0.47, respectively. The percentage volume of B-type starchgranules was significantly negatively correlated with pasting temperature, peak viscosity and finalviscosity, and the correlation coefficients were-0.33,-0.20and-0.43, respectively. A:B ratio wassignificantly positively correlated with pasting temperature (r=0.32), peak viscosity (r=0.26) and finalviscosity (r=0.46). In addition, the percentage volumes of A-type and B-type starch granules and A:Bratio were also significantly correlated with amylose content, and the correlation coefficients were-0.42,0.40and-0.43, respectively.2. QTL mapping for starch granule size distribution and its correlations with starch properties incommon wheatThree QTL for the percentage volume of A-type starch granules were mapped on chromosomes1DL,7BL and4AL, explaining5.6%,5.2%and3.8%of phenotypic variations, respectively. Although QTL on chromosome4AL was located near the Wx-B1locus, it is a different locus. No QTL was found onchromosomes1DL,4AL or7BL in common wheat previously, implying that the present QTL forpercentage volume of A-type starch granules are new.