Genotypes H1 and H2 are two ancient haplotypes on Lr10 locus,which is a resistance gene to wheat leaf rust.They are identified based on the presence of both Lr10 and RGA2 in full length(H1),and the absence of Lr10 and chromatin rearrangement of RGA2(H2)due to chromosome 1AS reorganization during species evolution.Both haplotypes contain several subhaplotypes.To understand the genetic diversity on Lr10 locus,we tested the frequencies of H1 and H2 haplotypes and their subhaplotypes in189 wheat cultivars and 58 breeding lines from various provinces of China.The H2 haplotype was dominant in the developed cultivars and breeding lines with the frequencies of 95.2%(180/189)and 96.6%(56/58),respectively.Five novel subhaplotypes were detected in the developed cultivars,namely H1-2,H2-4,H2-5,H2-6,and H2-7.In cultivars,subhaplotype H2-1 was the most frequent(69.3%),whereas subhaplotypes H2-3 and H2-6 had the lowest frequencies(0.5%).Among the five subhaplotypes detected in breeding lines,subhaplotype H2-1 had the highest frequencies(27.6%),whereas subhaplotypes H1-2 was the least frequent(3.5%).Interestingly,the subhaplotypes except for H2-1 and H2-2 were highly breeding location-dependent(P 0.05).These results support the hypothesis that both haplotypes have been maintained through a balanced polymorphism mechanism during wheat domestication.Furthermore,the five novel subhaplotypes suggest that genetic diversities resulting from recombination and other types of chromatin reorganizations(e.g.,origin of the H2 haplotype and polymorphism for the Lr10 locus)have been going on since the formation of the hexaploid wheat.Significantly,identification of the H1-2 subhaplotype is a clear evidence of occurrence of recombination between the two ancient haplotypes,which disagrees with the previous notion.Importantly,because the frequencies of H1 is lower than 5% in developed cultivars and breeding lines,actions for protecting germplasm with the H1 haplotype are highly recommended.

The objectives of this study were to construct a new linkage map of wheat using a recombinant inbred line (RIL) population derived from the cross between Shannong 01-35 and Gaocheng 9411 and locate quantitative trait loci for thousand-grain weight (TGW) using this map. The RIL population, consisting of 182 lines, was obtained via single-seed descendent method until the F 8 generation. The genetic map consisted of one TaGW2-CAPS,59 SSR, and442 DArT markers in 29 linkage groups, including 54 novel markers (44 DArT markers and 10 SSRs) assigned into 18 linkage groups. The total genetic length of the map was 4084.5 cM with an average interval distance of 8.13 cM. The 182 RILs and their parents were grown in four environments from 2008 to 2010, and QTLs associated with TGW were identified using mixed linear model based on both separated and joint environments. A total of seven QTLs were detected including three QTLs ( QGW4B-7 , QGW5B-20 , and QGW6A-29 ) commonly found using both methods. Three major QTLs, i.e., QGW4B-7 , QGW5B-12 , and QGW6A-29 , exhibited phenotypic contributions higher than 10%. These results suggest that the QTLs detected by using the successfully constructed genetic map are valuable in molecular marker-assisted selection in wheat.

Coleoptile length and radicle length are important indexes to evaluate stress resistance of wheat(Triticum aestivum L.) seedlings.For mapping quantitative trait loci(QTLs) for lengths of coleoptile and Radicle in wheat,a set of immortalized F2(IF2) population(168 lines) from Huapei 3× Yumai 57 double haploid(DH) lines was treated with distilled water(normal condition) and 10%,20%,and 30% of polyethylene glycol(PEG-6000).The coleoptile length(CL) and radicle length(RL) of the parents and the 168 IF2 lines were measured after 7 d of treatment.QTLs for CL and RL were detected using 323 SSR markers,which were distributed in the whole genome of wheat.Based on inclusive composite interval mapping(ICIM) method,we identified 11 additive QTLs for CL and 12 additive QTLs for RL under normal and the three stress conditions.Each locus explained 4.93%-35.37% of phenotypic variance.In the interval between Xcfd39.2 and Xcfd22.2 on chromosome 4B,QTL QCl4B had the phenotypic contribution of 35.37%.Another QTL QCl3D-a located between Xcfd223 and Xbarc323 on chromosome 3D was detected in both normal and 20% PEG-6000 treatments,which explained phenotypic variances of 7.83% and 11.74%,respectively.QTL QCl3D-b was located on the same chromosome and close to QCl3D-a.In the linkage groups 1A and 5A1,three and two QTLs associated with RL were detected respectively.On chromosome 6D,two QTLs for CL and RL were found in the interval between Xswes679.1 and Xcfa2129 and the interval between Xwmc412.1 and Xcfd49,respectively.The major QTLs identified can be applicable in marker-assisted selection in wheat breeding for coleoptile and root.

This study aimed at studying the molecular genetic basis of plant height (PH) heterosis in wheat. From a set of doubled haploid (DH) lines derived from Huapei 3 × Yumai 57, an “immortalized F2” population was constructed with 168 single crosses. The DH lines, IF2 population, and the parents were evaluated for plant height in 3 environments, i.e., in Tai'an, Shandong Province, China, in 2007 and 2008 cropping seasons and in Jiyuan, Henan Province, China in 2008 cropping season. Based on the genetic map of quantitative trait locus (QTL) constructed in a previous study, the heterosis of PH of wheat was analyzed using the composite interval mapping method. A total of 3 additive QTLs, 2 dominance QTLs, 4 pairs of epistatic QTLs (including additive by additive, additive by dominance, dominance by additive, and dominance by dominance), and 20 heterotic loci were detected for PH in the 3 environments. Two QTLs, QPh2D and QPh4D, were detected on chromosomes 2D and 4D with a minor interaction of additive by environment. In addition, several heterotic loci for PH except QPh2D were also identified on chromosome 2D in close regions with similar marker intervals. Of them, QTLs QPh2D-2 and QPh2D-7 explained the PH variance by 29.77% and 55.77%, respectively. Another QTL associated with PH heterosis, QPh7D-2, was mapped in the marker interval between Xwmc273.2 and Xcfd175 on chromosome 7D in the 3 environments. These results indicated that a few QTLs on chromosomes 2D, 4D, and 7D play an important role in PH heterosis in wheat. These loci have potential use for the improvement of PH in wheat breeding assisted with molecular markers.

Effective tiller number is one of the most important traits for wheat (Triticum aestivum L.) yield, but the inheritance of tillering is poorly understood. A set of 168 doubled haploid (DH) lines derivatives of a cross between two winter wheat cultivars (Huapei 3 and Yumai 57), and an immortalized F(2) (IF(2)) population generated by randomly permutated intermating of these DHs were investigated, and QTLs of tillering related to the maximum tillering of pre-winter (MTW), maximum tillering in spring (MTS), and effective tillering in harvest (ETH) were mapped. Phenotypic data were collected for the two populations from two different environments. Using inclusive composite interval mapping (ICIM), a total of 9 and 18 significant QTL were detected across environments for tillering in the DH and IF(2) populations, respectively. Four QTLs were common between two populations. A major QTL located on the 5D chromosome with the allele originating from Yumai 57 was detected and increased 1.92 and 3.55 tillers in MTW and MTS, respectively. QTLs (QMts6D, QEth6D) having a neighbouring marker interval at Xswes679.1 and Xcfa2129 on chromosome 6D was detected in MTS and ETH. These results provide a better understanding of the genetic factors for selectively expressing the control of tiller number in different growth stages and facilitate marker-assisted selection strategy in breeding.

小麦品种花培3号和豫麦57构建的DH群体的168个株系及亲本为材料,在正常发芽和20%PEG-6000模拟水分胁迫处理条件下测定小麦幼苗的胚芽鞘长、根长.利用完备区间作图法分析幼苗胚芽鞘长、幼根长的QTL.两种处理条件下共定位了8个控制胚芽鞘长加性QTL,其中位于染色体2A、4B和4D上的QCl2A、QCl4B和QCl4D在两种处理条件下均被检测到,可解释6.10%～16.31%的表型变异.两种条件下共定位了10个控制幼根长加性QTL,其中位于染色体6A上Xgwm82和Xwmc553区间的QRl6A在两种处理下均被检测到,可分别解释8.26%和9.74%的表型变异.在检测到的18对控制胚芽鞘长、根长的上位性互作位点中,大多数互作属于非等位QTL间的非加性QTL位点之间互作.因此在小麦材料的早期抗旱性筛选、分子育种时要同时考虑加性QTL和非加性QTL位点间的上位性互作.