A Consistent QTL for Flour Yield on Chromosome 3B in the Soft Winter Wheat Variety, Kitahonami

Abstract The soft winter wheat variety, Kitahonami, shows a superior flour yield in comparison to other Japanese soft varieties. In order to map quantitative trait loci (QTL) associated with the flour-yield trait, association mapping was performed using panel lines in Kitahonami's pedigree, along with leading varieties and advanced breeding lines. Using a mixed linear model corrected for kernel types and familial relatedness, 62 marker-trait associations were identified and classified into 21 QTLs. Five out of eight QTLs tested were validated by linkage analyses using three sets of doubled haploid populations from crosses in which Kitahonami was used as a parent. Among them, QTLs on 3B and 7A chromosome showed highly significant effects and consistency across the three populations. A joint linkage map of 3B showed that the QTL on this chromosome was located at the same interval across the populations. By applying a meta-analysis approach, we have succeeded in identifying QTLs with consistent contributions to high flour yield across various genetic backgrounds.

Introduction

Flour yield is of great interest to milling companies. Thus, breeding of wheat varieties with higher flour yield, in addition to enhancement of milling techniques, is important to flour milling industries. In 2006, a soft winter wheat variety, Kitahonami, was released in the Hokkaido prefecture of Japan (Yanagisawa et al. 2007). It has a superior flour yield compared to other Japanese soft varieties (Fig. 34.1) and has become a leading variety in the Hokkaido area. Kitahonami is also being used as a source of the high flour-yield trait in all Japanese wheat breeding programs. Mapping of quantitative trait loci (QTL) associated with the flouryield trait and identification of linked markers would accelerate the development of varieties with high flour yield.

QTL studies using bi-parental populations have been conducted within hard wheat populations or within populations derived from hybridizing hard and soft wheat. These studies have revealed that reliable QTLs for flour yield are located on 16 out of 21 chromosomes: 1B, 1D, 2A, 2B, 3A, 3B, 4A, 4B, 4D, 5A, 5B, 5D, 6B,

6D, 7A and 7D (Parker et al. 1999; Campbell et al. 2001; Smith et al. 2001; Lehmensiek et al. 2006; Fox et al. 2013). Interclass hybridization between soft and hard wheat indicated that the hardness locus Pinb on 5D had a strong influence on flour yield (Campbell et al. 2001). Fox et al. (2013) detected a QTL explaining the highest phenotypic variance close to the plant height locus, Rht-D1 located on 4D. For soft wheat populations, only a few studies have been reported to date. Using an association mapping approach, Breseghello and Sorrells (2006) detected weak QTLs associated with flour yield and break flour yield on 2D and 5B. One biparental population derived from two soft wheat cultivars revealed QTLs for flour yield, flour protein, softness equivalent, and solvent retention capacities (Smith et al. 2011), the majority of which were located on 1B and 2B. Carter et al. (2012)

Fig. 34.1 Distribution of flour yield for 65 winter wheat accessions used in this study

found that a large number of QTLs including QTLs for flour yield were located on 3B and 4D and coincided with traits for milling quality and starch functionality. Although these QTLs were detected with high confidence, few were detected in more than one study, indicating that flour yield is a complex trait strongly influenced by genetic background.

The objective of this study was to dissect genetic factors contributing to the high flour-yield trait of Kitahonami and to find effective QTLs and associated markers that can be used for MAS in our breeding programs.

 
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