Seed dormancy is one of the important factors controlling pre-harvest sprouting (PHS) resistance in wheat. We identified a major quantitative trait locus (QTL) for seed dormancy on the long arm of wheat chromosome 4A (4AL) via simple sequence repeat (SSR)-based genetic mapping using doubled haploid lines from a cross between Japanese PHS resistant variety 'Kitamoe' and the Alpine non-resistant variety 'Münstertaler' (K/M). The QTL explained 43.3% of total phenotypic variation for seed dormancy under greenhouse conditions. SSR markers flanking the QTL were assigned to the chromosome long arm fraction length 0.59-0.66 on the basis of chromosome deletion analysis, suggesting that the gene(s) controlling seed dormancy are probably located within this region. Under greenhouse conditions, the QTL explained 28.5 and 39.0% of total phenotypic variation for seed dormancy in Haruyutaka/Leader (HT/L) and OS21-5/Haruyokoi (O/HK) populations, respectively. However, in field conditions, the effect was relatively low or not significant in both the K/M and HT/L populations. These markers were considered to be widely useful in common with various genetic backgrounds for improvement of seed dormancy through the use of marker-assisted selection. Further detailed research using near isogenic lines will be needed to define how this major QTL interacts with environmental conditions in our area.
Seed dormancy is an important factor regulating preharvest sprouting (PHS) but is a complex trait for genetic analysis. We previously identified a major quantitative trait locus (QTL) controlling seed dormancy on the long arm of chromosome 4A (4AL) in common wheat. To transfer the QTL from the dormant lines 'OS21-5' and 'Leader' into the Japanese elite variety 'Haruyokoi', which has an insufficient level of seed dormancy, backcrossing was carried out through marker-assisted selection (MAS) using PCR-based codominant markers. Nineteen BC5F2 plants with homozygous alleles of 'OS21-5' or 'Haruyokoi' were developed and evaluated for seed dormancy under greenhouse conditions. The seeds harvested from plants with 'OS21-5' alleles showed a clearly high level of dormancy compared with seeds from plants with 'Haruyokoi' alleles. Additionally, the dormancy phenotype of BC3F3 seeds harvested from 128 BC3F2 plants with homozygous alleles of 'Leader' or 'Haruyokoi' showed a clear difference between these alleles. The QTL on 4AL confers a major gene, Phs1, which was mapped within a 2.6 cM region. The backcrossed lines developed in this study can be important sources for improving PHS resistance in Japanese wheat and for analyzing the mechanism of seed dormancy. MAS was useful for the development of near-isogenic lines in this complex trait, to facilitate the molecular dissection of genetic factors.
A ''two-line system'' using photoperiodsensitive cytoplasmic male sterility (PCMS) caused by Aegilops crassa cytoplasm under long-day photoperiods (=15 h) has been proposed as a means of producing hybrid varieties in common wheat (Triticum aestivum). The PCMS line is maintained by self-pollination under short-day conditions, and hybrid seeds can be produced through outcrossing of the PCMS line with a pollinator line under long-day conditions. Our previous studies revealed that PCMS lines showing complete male sterility under long-day conditions are necessary for practical hybrid wheat breeding, especially to obtain high hybrid purity in F 1 seeds. Furthermore, practical PCMS lines should have high seed fertility under short-day conditions, which is associated with female fertility. Wheat cv. Norin 26 with Ae. crassa cytoplasm exhibits high seed fertility under short-day conditions, and cv. Fujimikomugi with Ae. crassa cytoplasm shows high male sterility under long-day conditions. Here we developed practical PCMS lines derived from the F 1 generation of Norin 26 and Fujimikomugi (with Ae. crassa cytoplasm) that were then backcrossed to elite wheat lines.
To elucidate the effects of different glutenin subunit alleles on the parameters of wheat flour quality, we analyzed the dough and gluten properties using a doubled-haploid population derived from a cross between two wheat cultivars differing in the glutenin subunit loci except for Glu-D3, namely Grandin (Glu-A1b, Glu-B1c, Glu-D1d, Glu-A3f, Glu-B3h and Glu-D3a) and Kitamiharu 57 (Glu-A1a, Glu-B1i, Glu-D1a, Glu-A3c, GluB3b and Glu-D3a). Based on the analysis of the DH lines, no significant differences in the flour protein content were detected among the glutenin alleles. However, the Glu-D1 and Glu-B3 alleles exerted significant effects on the dough and gluten properties. The DH lines with the Glu-D1d or Glu-B3b alleles showed a significantly higher gluten index, determined using the Glutomatic system and longer dough development time determined using a mixograph. The Glu-D1d and Glu-B3b alleles additively increased the dough and gluten strength. The DH lines with the Glu-A1a allele also showed a significantly higher gluten index and longer dough development time than those with the Glu-A1b allele, though to a lesser extent. These results indicated that the Glu-B3b allele exerted similar effects on the dough and gluten strength as the Glu-D1d allele. Since the DH lines harboring the Glu-D1d and Glu-B3b alleles showed excessive values for the strength of dough and gluten, it was suggested that both the Glu-1 and Glu-3 allelic composition should be considered to improve the wheat flour quality.
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