Grain sorghum has been a significant contributor to global food security since the prehistoric period and may contribute even more to the security of both food and energy in the future. Globally, precise management techniques are crucial for increasing grain sorghum productivity. In China, with diverse ecological types, variety introduction occasionally occurs across ecological zones. However, few information is available on the effect of ecological type on genotype performance and how plant spacing configuration influences grain yield in various ecological zones. Hence, a series of two-year field experiments were conducted in 2020 and 2021 in four ecological zones of China, from the northeast to the southwest. The experiments included six widely adapted sorghum varieties under six plant spacing configurations (two row spacing modes: equidistant row spacing (60 cm) mode and wide (80 cm)-narrow (40 cm) row spacing mode; three in-row plant spacings: 10 cm, 15 cm, and 20 cm). Our results indicated that ecological type, variety, and plant spacing configuration had a significant effect on sorghum yield. Ecological type contributed the highest proportion to the yield variance (49.8%), followed by variety (8.3%), while plant spacing configuration contributed 1.8%. Sorghum growth duration was highly influenced by the ecological type, accounting for 87.2% of its total variance, whereas plant height was mainly affected by genotype, which contributed 81.6% of the total variance. All test varieties, developed in the south or north, can reach maturity within 94-108 d, just before fall sowing in central China. Generally, sorghum growth duration becomes longer when a variety is introduced from south to north. A late-maturing variety, developed in the spring sowing and late-maturing regions, possibly could not reach maturity in the early-maturing region. The row spacing modes had no significant affect on sorghum yield, but the equal-row spacing mode consistently caused higher yields with only one exception; this might imply that equal-row spacing mode was more advantageous for boosting sorghum yield potential. In contrast, decreasing in-row plant spacing showed significant positive linear associations with sorghum grain yield in most cases. In addition, these results demonstrated that sorghum is a widely adapted crop and enables success in variety introduction across ecological zones.

Few Chinese high yielding white-grained wheat cultivars possess sufficient dormancy to avoid pre-harvest sprouting (PHS). Because the field evaluation of PHS is difficult, the identification of informative molecular markers is a priority for improving the level of dormancy. In this report, the effectiveness of phenotypic and genotypic selection was compared. Four microsatellite loci Xbarc57, Xbarc294, Xbarc310 and Xbarc321, mapped on the short arm of chromosome 3A, were used for selection in white-grained wheat F5 lines which were also selected on the basis of their grain filling rate (GFR). One of these (later designated cv. Zhongmai911) was further selected on the basis of its allelic constitution at the four SSR loci. This cultivar combines a high level of PHS resistance with high grain yield. The results suggested that rapid GFR and PHS resistance can be bred simultaneously.

ABSTRACTTwo sets of bread wheat (Triticum aestivum L.) varieties and their respective founder parents (St2422/464 and Abbondanza) in China were genotyped at 481 microsatellite loci. The selection sweeps detected almost completely overlapped with one another across the two sets on the 21 chromosomes although a cluster analysis showed that they do represent distinct subpopulations with Fst = 0.0734 (minor allele frequency [MAF] = 0.1, –log10p = 5). About 38.7% of the loci appeared to have experienced some selection sweep. Important agronomic traits were usually associated with these selection sweep valleys. The alleles present at key loci in these valleys were often in common between the two founders. Marker–trait association based on three seasons of field data suggested the association of one, four, and six loci with, respectively, the number of fertile tillers per plant, grain number per spike, and thousand grain weight. Five, 14, and 21 loci were associated with the three yield components in two of the three seasons. We suggest that the breeding potential of a line can be predicted from its allelic state at certain critical marker loci, which represent major targets for breeding by design in wheat. Genotypic descriptions of major cultivars and the analytical approach we have described here provide a path toward the a priori selection of favorable breeding parents.

To identify QTLs related to thousand-grain weight （TGW） and validate its＇ stability in mul- tiple ecological environments, the F9：10 generation of 142 recombinant inbred lines （RILs） derived from the cross between Yu 8679 （large spike） and Heshangmai （small spike） were planted in eight ecological environments in Beijing （2006 and 2007）, Hefei （2007, 2008）, Chengdu （2007, 2008） and Taian （2009, 2010）. A genetic map comprising 170 SSR and 2 EST markers （Tx23-24 and Tx37-38） was constructed based on the 142 RII.s. According to the genetic map and phenotypic data, quantita- tive trait loci were identified for TGW using the composite interval mapping （CIM） method. A total of 35 QTLs located on chromosomes 1A, 1B, 2A, 2D, 3A, 3B, 4A, 4D, 5A, 5B, 6D, and 7D for TGW were identified over eight environments, which accounted for variations of TGW by 4. 36O//oo 16.80~//00. Especially, three QTI.s on chromosomes 1B （QTgw. nfcri-lB）, 2A （QTgw. nfcri-2A） and 3B （QTgw. nfcri-3B） could be detected in the most environments and could explain high phenotypic variation, the three QTLs may be effective and useful for farther exact location and MAS for high yield breeding.

Seed dormancy evaluated by germination index (GI) is often regarded as a main and pivotal component of observed genetic variation for pre-harvest sprouting (PHS). Improving seed dormancy can decrease or avoid PHS damage to wheat before harvest. However, it is difficult to accurately evaluate seed dormancy under field conditions. In this study, 4 simple sequence repeat markers (Xbarc57, Xbarc294, Xbarc310, and Xbarc321) on the short arm of chromosome 3A and a gene-based marker (Vp1-b2) on 3BL were used for genotyping 138 micro-core collections of Chinese wheat and landraces. Rich alleles were detected using these markers, and most of them were significantly correlated with GI value. A significant association between the 5 markers and seed dormancy was found according to General Linear Model. Vp1-b2 and Xbarc294 had larger effects on seed dormancy than other markers, which accounted for 65.8% and 61.2% of phenotypic variation, respectively. Combination of the 5 marker gave the largest estimation of GI variation in the 138 wheat genotypes (95.9%), followed by marker combination Vp1-b2/Xbarc294 (89.1%), and marker combination Vp1-b2/Xbarc321 had the smallest effect (79.4%). This result indicated that seed dormancy of tested genotypes was mainly associated with 2 loci on 3AS and 3BL.

Pre-harvest sprouting (PHS) in wheat is an important problem that results in significant economic loss to farmers. In this study,the PHS resistances of 76 Chinese wheat cultivars collected from ten wheat growing provinces were identified; Moreover,the distribution of three molecular markers Vp1B3,Xbarc310 and Barc294 associated with PHS resistance in the 75 cultivars was identified,aimed to evaluate the efficiency of these markers in selecting genotypes with higher PHS resistances. The results indicated that there is significant difference of PHS resistances in above wheat cultivars. The allelic variations of Vp1 gene are not associated with the PHS resistance; Vp1B3 was non-specific and unsuitable for marker assisted selection ( MAS) in breeding. The 3As QTL ( QPhs-3AS) is a critical component of seed dormancy,Xbarc310 and Barc294 were specific and suitable for MAS. The usefulness of current information in wheat breeding is discussed.

【Objective】 QTL associated with grain size and related traits was identified and the phenotypic effects of them were estimated. The stability of QTL across different environments were detected. 【Method】 Using a set of 142 recombinant inbred lines (RILs) derived from Chinese winter wheat varieties Yu8679 and Heshangmai, five agronomic traits of grain length (GL), grain width (GW), grain thickness (GT), grain volume (GV) and 1000-grain weight (TGW) were evaluated in four different ecological environments of Beijing (2006 2007), Hefei (2007) and Chengdu (2007), respectively. Based on 142 RILs, a genetic map comprising 170 SSR markers and two EST markers (Tx23-24 and Tx37-38) was generated. According to the genetic map and phenotypic data, quantitative trait loci (QTL) were located for these agronomic traits using the composite interval mapping method. 【Result】 A total of 93 QTL involving all wheat chromosomes except 1D and 6A were identified for these five traits over four environments. Among them, 17, 16, 18, 21 and 21 QTL for GL, GW, GT, GV and TGW were identified, respectively. In addition, 18 genomic regions with plenty of QTL were detected on 1A, 1B, 2A, 2D, 3A, 3B, 5A, 5B, 5D, 6A, 6D, 7B and 7D in this study. 【Conclusion】In the present study, 93 QTL for grain size and related traits were detected, which will provide useful information for molecular assistant selection (MAS) in wheat genetic improvement.

【Objective】 The purpose of this study was to reveal genetic relationship between the large-scale cultivated wheat varieties and the founder genotypes(cornerstone breeding parents) and illuminate the role of the founder genotypes in breeding at genomic level.【Method】 Sixty-six large-scale planted varieties and 13 founder genotypes were genotyped at 481 SSR loci by the ABI 3730.【Result】 Analyses of principal coordinate(PCO) and neighbor-joining cluster based on the genotyping data showed that the 66 large-scale planted varieties were clustered into six major groups.In each group,there is at least one founder.Within each group,most of the large-scale planted varieties are the descendents of the founder.Varieties from the same province usually jointed into one group.Two founders,Bima 4 and St2422-464 convey more alleles favored in breeding than their sister lines,Bima 1 and St1472-506,respectively.Usually,the older cornerstone breeding parents are the founders for the new ones.Among sister lines,the new founder has more difference than large-scale cultivated varieties to their founder genotype.【Conclusion】 Therefore,innovation and enhancement of germplasm is the base for breeding large-scale planted varieties.It should occupy proper portion in national breeding program.

Genetic diversity among 5029 accessions representing a proposed Chinese wheat core collection was analyzed using 78 pairs of fluorescent microsatellite (SSR) primers mapped to 21 chromosomes. A stepwise hierarchical sampling strategy with priority based on 4×105 SSR data-points was used to construct a core collection from the 23090 initial collections. The core collection consisted of 1160 accessions, including 762 landraces, 348 modern varieties and 50 introduced varieties. The core accounts for 23.1% of the 5029 candidate core accessions and 5% of the 23090 initial collections, but retains 94.9% of alleles from the candidate collections and captures 91.5% of the genetic variation in the initial collections. These data indicate that it is possible to maintain genetic diversity in a core collection while retaining fewer accessions than the accepted standard, i.e., 10% of the initial collections captured more than 70% of their genetic diversity. Estimated genetic representation of the core constructed by preferred sampling (91.5%) is much higher than that by random sampling (79.8%). Both mean genetic richness and genetic diversity indices of the landraces were higher than those of the modern varieties in the core. Structure and principal coordinate analysis revealed that the landraces and the modern varieties were two relatively independent subpopulations. Strong genetic differentiation associated with ecological environments has occurred in the landraces, but was relatively weak in the modern cultivars. In addition, a mini-core collection was constructed, which consisted of 231 accessions with an estimated 70% representation of the genetic variation from the initial collections. The mini-core has been distributed to various research and breeding institutes for detailed phenotyping and breeding of genetic introgression lines.

用分布于21个连锁群上的78个微卫星标记(SSR),对我国5029份普通小麦初选核心种质进行基因型分析,收集了40万条SSR数据.以此为基础,采用适当调整的分层分组代表性取样法(即分区取样时,对材料遗传多样性高的地区略增加取样量,反之略减少取样量;著名品种、重要育种亲本和携带稀有等位变异的材料优先入选),构建了由1160份材料组成的小麦核心种质(库),其中地方品种762份、育成品种348份、国外引进品种50份.核心种质占初选核心种质的23.1%,占整体种质(23090份)的5%,遗传代表性估计值为91.5%.核心种质中地方品种的遗传多样性明显高于育成品种.群体遗传结构及主坐标分析均显示我国地方品种和育成品种是两个相对独立的组群.来源于不同生态区的地方品种遗传分化十分明显,而育成品种分化相对较弱.此外还构建了由231份材料组成的微核心种质,其占整体种质的1%,但遗传代表性估计值接近70%.最后就核心种质构建的意义和取样策略进行了讨论.

<正>Besides the natural selection, the crops cultivated today have experienced two episodes of strong artifi cial selection, domestic and modern breeding. Domestication led to giant genetic structure differentiation between

The duration and rate of grain filling determine the individual grain size, thousand-grain weight (TGW), and final grain yield. Several reports have focused on the physiological basis of grain filling in wheat (Triticum aestivum L.), but rare on the genetic mechanism and QTL mapping due to its complexity. To identify QTLs related to grain filling, the F7:8 generation of 142 recombinant inbred lines (RILs) derived from the cross between Yu 8679 (large spike) and Heshangmai (small spike) were planted in four ecological environments in Beijing (2006 and 2007), Hefei (2007), and Chengdu (2007). Three agronomic traits including mean grain filling rate (GFRmean), maximum grain filing rate (GFRmax), and TGW were evaluated. A genetic map comprising 170 SSR and 2 EST markers (Tx23-24 and Tx37-38) was constructed based on the 142 RILs. According to the genetic map and phe-notypic data, quantitative trait loci were identified for these agronomic traits using the composite interval mapping (CIM) method. A total of 54 QTLs located on chromosomes 1A, 1B, 2A, 2D, 3A, 3B, 3D, 4A, 4D, 5A, 5B, 6D, and 7D for the three traits were identified over four environments. Among them, 17 for GFRmean, 16 for GFRmax, and 21 for TGW, accounted for variations of GFRmean, GFRmax, and TGW by 7.17–20.83%, 6.31–15.95%, and 4.36–16.80%, respectively. Ten genomic sections involving chromosomes 1A, 1B, 2A, 3B, 4D, 6D, and 7D with were detected. These QTLs with pleiotropic effects are useful for understanding the relationship between grain filling and other related grain yield traits at gene level.

A total of 1 739 Chinese wheat landraces were screened for the Waxy gene mutations with two STS,one SSR and one gene specific marker published in previous researches.Among of the landraces,3 were null Wx-A1 mutants,25 were null Wx-B1 mutants,and 3 were null Wx-D1 mutants.Different null types of Waxy genes were also certified by SDS-PAGE of waxy proteins,containing that these markers were effective to verify mutants and normal alleles at waxy loci.These markers can also be used in marker-assisted selection in breeding program.Furthermore,based on our findings,we recommend some accessions with different Waxy mutations to breeders.genotypes of Waxy genes of these materials were also released in this paper.

Besides the natural selection, the crops cultivated today have experienced two episodes of strong artificial selection, domestic and modern breeding. Domestication led to giant genetic structure differentiation between cultivars and their wild species, while modern breeding made further genetic structure differentiation between the modern varieties and the landraces. In a population, diversity of the loci under strong selection is significantly lower than that of other loci. At the same time, diversity in the genomic regions flanking these selected loci also declines in the process of selection. This phenomenon is called hitchhiking effects or selection sweep in genetics. Genomic regions with selection sweep (haplotype block) could be detected after draft genome scanning (genome typing) with molecular markers in a number of released varieties or natural populations. Marker/trait association analysis in these regions would detect the loci (or QTLs) even the favored alleles (genes) in breeding or natural adaptation. Fine scanning of these genomic regions would help to determine the sizes of haplotype blocks and to discover the key genes, thereby providing very valuable information for isolation of the key genes and molecular design of new varieties. Establishment of high density genetic linkage maps in the major crops and availability of high throughput genotyping platform make it possible to discover agronomic important genes through marker/trait association analysis. On the basis of available publications, we give a brief introduction of the hitchhiking effect mapping approach in this paper using plant height, 1000-grain weight, and phosphorus-deficiency tolerance as examples in wheat.

Most agronomic traits such as yield, quality and stress-tolerance of crops are quantitative traits. It is not easy to dissect genetic basis of these traits because they are controlled by multi-genes that are affected by environmental factors. Hitchhiking mapping offers a new method for identifying of loci controlling those traits and assessing their allelic variations. Marker-trait association analysis based on the hitchhiking effects will play an important role in dissection of complex traits. Combination of quantitative trait loci (QTL) mapping with marker-trait association analysis will facilitate dissection of complex traits, resulting in important information and markers for molecular breeding by design in crops. In this review, we presented a brief introduction of hitchhiking effects, marker-trait association analysis and practical considerations.

Genetic diversity of 1680 modern varieties in Chinese candidate core collections was analyzed at 78 SSR loci by fluorescence detection system. A total of 1336 alleles were detected, of which 1253 alleles could be annotated into 71 loci. For these 71 loci, the alleles ranged from 4 to 44 with an average of 17.6, and the PIC values changed from 0.19 to 0.89 with an average of 0.69. (1) In the three genomes of wheat, the average genetic richness was B > A > D , and the genetic diversity indexes were B > D > A . (2) Among the seven homoeologous groups, the average genetic richness was 2=7>3>4>6>5>1, and the genetic diversity indexes were 7>3>2>4>6>5>1. As a whole, group 7 possessed the highest genetic diversity, while groups 1 and 5 were the lowest. (3) In the 21 wheat chromosomes, 7 A , 3 B and 2 D possessed much higher genetic diversity, while 2 A , 1 B , 4 D , 5 D and 1 D were the lowest. (4) The highest average genetic diversity index existed in varieties bred in the 1950s, and then it declined continually. However, the change tendency of genetic diversity among decades was not greatly sharp. This was further illustrated by changes of the average genetic distance between varieties. In the 1950s it was the largest (0.731). Since the 1960s, it has decreased gradually (0.711, 0.706, 0.696, 0.695). The genetic base of modern varieties is becoming narrower and narrower. This should be given enough attention by breeders and policy makers.

对我国小麦育成品种初选核心种质(1680份)的78个微卫星标记(SSR)位点进行了扫描, 并就此对50年来育成品种的遗传多样性进行了评价和分析, 得到以下结果和结论: (ⅰ) 74对SSR荧光引物共检测到1336个等位变异, 其中1253个等位变异可以定位在71个位点上. 这71个位点上检测到的每个位点等位变异数为4～44个, 平均17.6个; 多态性信息指数(PIC)为0.19～0.89, 平均为0.69. (ⅱ) 三个基因组的平均等位变异丰富度为B>A>D, 遗传多样性指数为B>D>A. (ⅲ) 7个部分同源群的平均等位变异丰富度为2=7>3>4>6>5>1, 遗传多样性指数为7>3>2>4>6>5>1. 结合两个指标分析, 第7部分同源群具有最高的多样性, 而1, 5群多样性最低. (ⅳ) 21条染色体中, 7A, 3B和2D三条染色体遗传多样性较高, 而2A, 1B, 4D, 5D和1D的遗传多样性偏低. (ⅴ) 育成品种遗传多样性指数以50年代的最高, 以后越来越低, 但年代间变化较平缓; 品种间平均遗传距离以50年代最高(0.731), 以后逐渐减小, 各年代依次为0.711, 0.706, 0.696和0.695. 品种遗传基础狭窄化问题日趋突出, 应引起有关部门和育种家的关注.

Candidate core collections of common wheat ( Triticum aestivum L. ) were established based on the geographical regions, ecotypes, 21 agronomic and botanic characters of basic collections (entire). The modern varieties were divided into 10 regions, the landrace into 28 sub-regions. In each region or sub-regions, numbers of entries were decided based on the square root of the basic collections with minor adjustment according to the genetic diversity and genetic richness indexes. Varieties or lines having made great contribution in the national wheat breeding and production are priority entries in sampling. The candidate core collections were established after all entries were re-planted and checked in the field. In the candidate core collections, there are 3283 landraces, and 1684 modern varieties, which takes 28.18% and 14.9% of the basic collections respectively. We are going to concentrate the candidate core collections to 10% of the basic collection by molecular markers. They will be the core collections of Chinese wheat germplasm. Statistics showed that there was no significant difference on variation between the candidate core collection and the basic collections except the awn and glumes. The corner mountainous region between the Southern Shaanxi and the Western Hubai, valley along Fenghe and Wei-he are the genetic diversity center of Chinese wheat landrace. In the modern varieties, Southwestern winter wheat region and Huang-huai winter wheat region have the highest genetic diversity.