SUMMARY Flour whiteness (FW) is an important factor in assessing flour quality and determining the end product quality. It is an integrated sensory indicator reflecting flour colour and is negatively correlated with protein content. In order to dissect the genetic relationship between FW and its five related traits at the quantitative trait locus (QTL)/gene level, a recombinant inbred line population was evaluated under three environments. Quantitative trait loci for FW were analysed by unconditional and conditional QTL mapping. Four unconditional additive QTLs and 16 conditional additive QTLs were detected across the three environments. Of these QTLs, only one major additive QTL (Qfw1D1-1) was consistently identified using both unconditional and conditional QTL analysis. This QTL was independent of flour colour a* (a function of red-green with a positive a* for redness and negative for greenness) and b* (a green-blue value with positive value for yellowness and negative for blueness) and was only slightly affected by flour protein content. A minor additive QTL (Qfw4A-4) was also detected using these two QTL mapping methods, being independent of flour colour a* and b*. Five unconditional and ten conditional epistatic minor QTLs were detected, from which only one pair (Qfw3A-10/Qfw6B-6) was identified by both unconditional and conditional QTL mapping, also independent of flour colour a* and b*. The major QTL (Qfw1D1-1) identified in the current study for the first time can be used for improving wheat FW in marker-assisted breeding.

本研究以花培3号×豫麦57的168个双单倍体(doubled haploid,DH)群体为材料,根据2年12个环境下千粒重性状的表型数据和含有323个位点的分子遗传图谱,对千粒重性状进行了QTL分析.结果共检测到40个QTL,主要集中在染色体2D、3A、4D、5B、6A和7D上.其中,2010年莱阳点3种施氮期下检测到8个QTL,2010年泰安试验点共检测到13个QTL,2011年济源点检测到12个QTL,2011年泰安试验点检测到7个QTL,单个QTL所解释的表型变异介于4.19％～23.14％之间.亲本花培3号对于千粒重的贡献占主导地位.Qtgw3A-2、Qtgw5B、Qtgw6A-1和Qtgw7D-1在三个施氮期都检测到,说明这些QTL是氮肥对千粒重影响较大的QTL.Qtgw3A-2、Qtgw4D、Qtgw6A-1、Qtgw7D-1等在多个试验点均能检测到,说明这些QTL是稳定表达的QTL.总之,影响千粒重的QTL数目及其QTL表达效应在不同施氮期下有很大的变化,说明不同施氮期对千粒重基因的表达存在特异性.小麦育种中,上述结果可为今后合理追施氮肥,增加粒重和产量及千粒重的分子标记辅助选择提供理论依据.

Wheat thousand kernel weight (TKW) is a complex trait, and is largely controlled by several kernel traits, including kernel length (KL) and kernel width (KW). In order to reveal the genetic relationship between TKW and these kernel traits (KW and KL) as accurate as possible, we applied both unconditional and conditional mapping analyses to three distinct genetic populations, one DH population and two RIL populations. This report describes the identifications of 36 unconditional and conditional additive QTLs and 30 pairs of unconditional and conditional epistatic QTLs, all of which are closely associated with TKW. While the conditional additive locus Qtkw1B, detected in the RIL2 population, exhibited the largest contribution, explaining 14.12 % of TKW variance, the unconditional epistatic QTLs Qtkw3A-2/Qtkw5B.1, detected in the DH population, accounted for 11.95 % of phenotypic variance. This study also showed that, compared with unconditional mapping, conditional mapping resulted in very different numbers and different extent of effects of additive and epistatic QTLs that were associated with TKW when TKW was conditioned on kernel traits (KW and KL). These data strongly suggest that KW and KL indeed play a significant role in determining TKW. Furthermore, we demonstrated that the effects of the 25 additive QTLs for TKW were either entirely or largely determined by KW, while the effects of the other 25 additive QTLs for TKW were either entirely or largely affected by KL. We conclude that the conditional mapping can be useful for a better understanding of the interrelationship between the yield contributing traits at the QTL level.

Grain weight is an important factor contributing to grain yield in wheat. Markers closely linked to grain weight could be used in marker-assisted selection (MAS) to accelerate the wheat breeding process. In this paper, a second backcross recombinant inbred line (BC2F4) population, a recombinant inbred line (RIL) population, and one natural population were used to study the relationship between allelic variants of the grain weight gene TaGW2-6A and grain weight, width, and length with the goal of verifying the feasibility using the functional marker Hap-6A-P1/P2 in MAS. The differences in average grain weight, width, and length between haplotypes Hap-6A-G and Hap-6A-A were 8.09 g, 0.22 mm, and 0.38 mm, respectively, in the BC2F4 population; 4.01 g, 0.11 mm, and 0.10 mm in the RIL population; and 3.95 g, 0.10 mm, and 0.20 mm in the natural population. All the differences were significant. Sequencing results of the products of second round PCR indicated that a 167 bp TaqI restriction fragment had been generated from small-grain-size materials because of three TaqI restriction sites (TCGA). However, the large-grain-size variant generated a 218 bp fragment due to a single-nucleotide mutation (SNP) (TCGA → TCGG) at the third site. TaGW2-6A expression levels were negative with respect to grain width, length, and weight. For this reason, Hap-6A-G was considered a superior allele. These results contradict those of a previous study, which showed Hap-6A-A to be significantly associated with wider grain and higher grain weight.

Protein and starch are the most important traits in determining processing quality in wheat. In order to understand the genetic basis of the influence of Waxy protein （Wx） and high molecular weight gluten subunit （HMW-GS） on processing quality, 256 recombinant inbred lines （RILs） derived from the cross of waxy wheat Nuomai 1 and Gaocheng 8901 were used as mapping population. DArT （diversity arrays technology）, SSR （simple sequence repeat）, HMW-GS, and Wx markers were used to construct the molecular genetic linkage map. QTLs for mixing peak time （MPT）, mixing peak value （MPV）, mixing peak width （MPW）, and mixing peak integral （MPI） of Mixograph parameters were evaluated in three different environments. The genetic map comprised 498 markers, including 479 DArT, 14 SSR, 2 HMW-GS, and 3 Wx protein markers, covering 4 229.7 cM with an average distance of 9.77 cM. These markers were identified on 21 chromosomes. Eighteen additive QTLs were detected in three different environments, which were distributed on chromosomes 1A, 1B, 1D, 4A, 6A, and 7D. QMPT-1D.1 and QMPT-1D.2 were close to the Glu-D1 marker accounting for 35.2, 22.22 and 36.57% of the phenotypic variance in three environments, respectively. QMPV-1D and QMPV-4A were detected in all environments, and QMPV-4A was the nearest to Wx-B1. One minor QTL, QMPI-1A, was detected under three environments with the genetic distances of 0.9 cM from the nearest marker Glu-A1, explaining from 5.31 to 6.67% of the phenotypic variance. Three pairs of epistatic QTLs were identified on chromosomes 2D and 4A. Therefore, this genetic map is very important and useful for quality trait related QTL mapping in wheat. In addition, the finding of several major QTLs, based on the genetic analyses, further suggested the importance of Glu-1 loci on dough mixing characteristics.

Two hundred and ninety F9 recombinant inbred lines (RILs) derived from the bread wheat cultivar Gaocheng 8901 and the waxy wheat cultivar Nuomai 1 were used in determining the high-molecular-weight glutenin subunit (HMW-GS) and waxy protein subunit combinations and their effects on the dough quality and texture profile analysis (TPA) of cooked Chinese noodles. Seven alleles were detected at Glu-1 loci. There were two alleles found at each of the Wx-A1, Wx-B1 and Wx-D1 loci. Eight allelic combinations were observed for HMW-GS, LMW-GS and waxy proteins, respectively. Both the 1/7+8/5+10 and 1/7+8/5+12 combinations contributed to dough elasticity, and the 1/7+8/5+10 combination also provided better TPA characteristics. Compared to Wx protein, HMW-GS was more important on dough alveogram properties. LMW-GS significantly affected springiness and cohesiveness; HMW-GS mainly affected the hardness; Wx×LMW-GS significantly affected the springiness, cohesiveness and chewiness; HMW-GS×Wx×LMW-GS mainly influenced the springiness and chewiness. But HMW-GS×LMW-GS only affected the spinginess. These indicated the TPA of noodles was significantly affected by the interactions between glutenin and Wx proteins.

The glutenin and waxy loci of wheat are important determinants of dough quality. This study was conducted to evaluate the effects of high-molecular-weight glutenin (HMW-GS) and waxy alleles on dough-mixing properties. Molecular mapping was used to investigate these effects on Mixograph properties in a population of 290 (Nuomai1 × Gaocheng8901) recombinant inbred lines (RILs) from three environments in the harvest years 2008, 2009 and 2011. The results indicated the following: (i) the Glu-A1 and Glu-D1 loci have greater impacts on Mixograph properties compared to the Wx-1 loci and the effects of Glu-D1d and Glu-D1h on dough mixing are better than those of Glu-D1f and Glu-D1new1 in this population; (ii) the interactions between the Glu-1 and Wx-1 loci affected some traits, especially the midline peak value (MPV), and the lack of Wx-B1 or Wx-D1 led to increased MPV for all types of Glu-1 loci; and (iii) 30 quantitative-trait loci (QTL) over nine wheat chromosomes were identified with ICIM analysis based on the genetic map of 498 loci. Eight major QTL and 16 QTL in the Glu-1 loci from the three environments were found. The major QTL clusters were associated with the Glu-1 loci, and also were found in two regions on chromosome 3B and one region on chromosome 6A, which is one of the novel chromosome regions influencing dough-mixing strength. The two QTL for MPV are located around Wx-B1 on chromosome 4A. QMPT-1D.1, QMPI-1D.1 and Q8MW-1D.1 were stable in different environments and could potentially be used in molecular marker-assisted breeding.

As one of the most effective enzymatic modification methods of protein, papain hydrolysis is applied widely in food production, accompanying starch pasting frequently in order to improve industrial quality. Effects of the papain hydrolysis on flour pasting properties were investigated in five papain/flour concentrations and five time-treatments. The structure of starch and protein networks in slurry was investigated under microscope before and after pasting. Results showed that papain hydrolysis influenced the pasting properties of wheat flour significantly through affecting structural characteristics, amylase activity and exothermic transition, especially during the early stage of hydrolysis. Peak viscosity, trough, final, integral area, and setback significantly decreased along with the increasing concentration of papain. Both hydrolysis time and concentration of papain had obviously effect on the breakdown. Pasting temperature and pasting time increased significantly with the enhancement of papain concentration. Hydrolysis time exerted minor effect on the pasting temperature and pasting time. The average peak time was slightly prolonged by lower concentration of papain, otherwise slightly shortened by higher concentration.

The dwarf-male-sterile wheat is unique to China and has been improved by introducing good germplasm. In order to clear the subunits background of Dwarf-Male-Sterile wheat, sodium dodecyl sulphate polyacrylamide-gel electrophoresis (SDS-PAGE) was used to detect the high and low molecular weight glutenin subunits (HMW-GS and LMW-GS) compositions in BC(1)F(1), F(2) and F(3) generations from Dwarf-Male-Sterile wheat. Twenty-five alleles and 49 HMW-GS compositions at the Glu-1 loci were detected in different generations. Null and subunit 1 were mainly existed at Glu-A1, and 7 + 8 and 7 + 9 were primarily detected at Glu-B1 in different generations. Subunit combination 5 + 10 mainly appeared in BC(1)F(1), while 2 + 12 major presented in F(2) and F(3) generations. HMW-GS compositions null, 7 + 8, 5 + 10 and null, 7 + 9, 5 + 10 showed higher frequencies than other banding patterns, followed by null, 14 + 15, 5 + 10 and null, 7 + 9, 2 + 12 combinations. In addition, some rare subunit combinations such as 14 + 15, 13 + 16, 17 + 18, 4 + 12, 2 + 10 and 5 + 12 were found in different generations. Eighteen alleles and 51 LMW-GS compositions at Glu-3 loci were found in different generations. Glu-A3a and Glu-B3d showed higher frequencies than others among three generations. There were mainly a, b, c alleles at Glu-D3. Thirty, 31 and 14 different combinations were detected in BC1F1, F2 and F3 populations, respectively. There were some good combinations such as A3d/B3h, A3d/B3d/D3a, A3b/B3b/D3a, A3a/B3d/D3a for different quality characteristics. So some desirable subunit combinations could be selected from different generations and new cultivars with good quality under distinct subunits background should be bred from Dwarf-Male-Sterile wheat in future.