小麦条锈菌分子生态学研究进展

小麦条锈病是危害最严重的小麦流行性病害之一,小麦条锈菌的生态学研究对制定合理的防治策略和抗锈育种具有重要意义.近十几年来,DNA分子标记技术被应用于小麦条锈菌的群体遗传学研究,推动了小麦条锈菌分子生态学研究的快速发展,为揭示小麦条锈菌的群体生态特性开辟了一个新的途径.本文系统介绍小麦条锈菌分子生态学研究的主要进展,并就我国当前研究的局限性和发展趋势进行了分析.     

Breeding for abiotic stresses for sustainable agriculture

Using cereal crops as examples, we review the breeding for tolerance to the abiotic stresses of low nitrogen, drought, salinity and aluminium toxicity. All are already important abiotic stress factors that cause large and widespread yield reductions. Drought will increase in importance with climate change, the area of irrigated land that is salinized continues to increase, and the cost of inorganic N is set to rise. There is good potential for directly breeding for adaptation to low N while retaining an ability to respond to high N conditions. Breeding for drought and salinity tolerance have proven to be difficult, and the complex mechanisms of tolerance are reviewed. Marker-assisted selection for component traits of drought in rice and pearl millet and salinity tolerance in wheat has produced some positive results and the pyramiding of stable quantitative trait locuses controlling component traits may provide a solution. New genomic technologies promise to make progress for breeding tolerance to these two stresses through a more fundamental understanding of underlying processes and identification of the genes responsible. In wheat, there is a great potential of breeding genetic resistance for salinity and aluminium tolerance through the contributions of wild relatives.     

Sink-limitation to yield and biomass: a summary of some investigations in spring wheat

Yield potential can be expressed as a product of light interception, radiation use efficiency (RUE), and the partitioning of biomass to grain yield, or harvest index (HI). Traits related to early or late light interception have not been shown to be associated with genetic improvement of spring wheat yield in favourable environments. It is, however, well established that yield improvement is largely a result of increased HI, although the most recent studies comparing genetic progress in HI over time in spring wheat indicate that it has not made any additional progress since the mid 1980s. These observations suggest that future genetic progress in yield will most likely be achieved by focusing on constraints to RUE. Considering the possibility that RUE may be influenced indirectly by sink limitation, it is apparent that biomass may be increased by increasing grain number, for example. Experiments with high yielding spring wheat lines containing the alien translocation 7DL.7Ag showed increased grains m‐2 (15%), yield (12%), and biomass (9%) compared with controls. The translocation was also associated with a larger investment in spike mass at anthesis (15%), more grains/spike (10%), and increased flag‐leaf photosynthetic rate during grain‐filling (20%). The data suggest that increased biomass in 7DL.7Ag lines was due to significantly increased RUE post‐anthesis, as a result of a larger kernel number (sink) that increased the demand for photosynthesis during grain‐filling. The hypothesis that increased photosynthesis and RUE may respond directly to a larger number of grains/spike was tested experimentally by imposing a light treatment during boot stage. The treatment was associated with a small increase (5%) in the proportion of biomass invested in spike mass at anthesis, reflected by on average three extra grains/spike at maturity. The treatment was associated with 25% more yield and 22% more biomass than controls, while carbon assimilation rate measured on flag‐leaves during grainfilling was 10% higher than controls. The results suggest that RUE can be increased indirectly by increasing sink strength and that the current yield limiting process in spring wheat is the determination of kernel number. Experimental data are presented on how spike fertility may be increased through breeding, for example by introgression of the multi‐ovary trait to increase grain number per spikelet. In addition, results of analysis of the physiological bases of genotype × year interaction in high yield environments are presented in the context of how such information can provide a focus for genetic studies of sink limitation.     

Phenotypic and genetic analysis of spike and kernel characteristics in wheat reveals long-term genetic trends of grain yield components

Key message

Phenotypic and genetic analysis of six spike and kernel characteristics in wheat revealed geographic patterns as well as long-term trends arising from breeding progress, particularly in regard to spikelet fertility, i.e. the number of kernels per spikelet, a grain yield component that appears to underlie the increase in the number of kernels per spike.

Abstract

Wheat is a staple crop of global relevance that faces continuous demands for improved grain yield. In this study, we evaluated a panel of 407 winter wheat cultivars for six characteristics of spike and kernel development. All traits showed a large genotypic variation and had high heritabilities. We observed geographic patterns for some traits in addition to long-term trends showing a continuous increase in the number of kernels per spike. This breeding progress is likely due to the increase in spikelet fertility, i.e. the number of kernels per spikelet. While the number of kernels per spike and spikelet fertility were significantly positively correlated, both traits showed a significant negative correlation with thousand-kernel weight. Genome-wide association mapping identified only small- and moderate-effect QTL and an effect of the phenology loci Rht-D1 and Ppd-D1 on some of the traits. The allele frequencies of some QTL matched the observed geographic patterns. The quantitative inheritance of all traits with contributions of additional small-effect QTL was substantiated by genomic prediction. Taken together, our results suggest that some of the examined traits were already the basis of grain yield progress in wheat in the past decades. A more targeted exploitation of the available variation, potentially coupled with genomic approaches, may assist wheat breeding in continuing to increase yield levels globally.

     

小麦抗赤霉病外源种质的创制和育种利用

小麦赤霉病是危害小麦安全生产的重要病害之一,种植抗病品种是防治赤霉病最经济有效的手段。目前在生产上应用的抗源很少,越来越多的研究者将目光转移到小麦的近缘属种,寻找新的抗源以及寻求新的育种突破。携带抗性基因的外源染色体可以通过染色体工程手段以附加系、代换系和易位系等形式导入小麦。综述了将大赖草等多个小麦近缘种的抗赤霉病基因导入普通小麦、创制抗病外源种质和育种利用的最新研究进展,以期为小麦抗赤霉病育种提供参考信息。     

小麦低分子量麦谷蛋白亚基功能标记研究进展

小麦是我国主要的粮食作物之一,籽粒中的低分子量麦谷蛋白对于小麦面包的加工品质具有重要的作用。近年来,利用分子标记技术检测小麦低分子量麦谷蛋白亚基（low molecular weight glutenin subunit,LMW-GS）的类型和组成已成为小麦品质改良的研究热点之一。主要综述了小麦低分子量麦谷蛋白亚基基因和蛋白质的结构特征、分类以及功能标记的研究进展,讨论了开发利用小麦Glu-A3、Glu-B3、Glu-D3位点LMW-GS功能标记的意义及存在的问题,并强调了LMW-GS分子标记检测技术的革新及亚基类型的完善对小麦品质改良的重要性,以期加速LMW-GS功能标记在优质小麦育种工作中的应用进程。     

<Emphasis Type="Bold">Zinc nutrition in wheat-based cropping systems</Emphasis>

Background

Zinc (Zn) deficiency is one of the most important micronutrient disorders affecting human health. Wheat is the staple food for 35% of the world’s population and is inherently low in Zn, which increases the incidence of Zn deficiency in humans. Major wheat-based cropping systems viz. rice–wheat, cotton–wheat and maize–wheat are prone to Zn deficiency due to the high Zn demand of these crops.

Methods

This review highlights the role of Zn in plant biology and its effect on wheat-based cropping systems. Agronomic, breeding and molecular approaches to improve Zn nutrition and biofortification of wheat grain are discussed.

Results

Zinc is most often applied to crops through soil and foliar methods. The application of Zn through seed treatments has improved grain yield and grain Zn status in wheat. In cropping systems where legumes are cultivated in rotation with wheat, microorganisms can improve the available Zn pool in soil for the wheat crop. Breeding and molecular approaches have been used to develop wheat genotypes with high grain Zn density.

Conclusions

Options for improving grain yield and grain Zn concentration in wheat include screening wheat genotypes for higher root Zn uptake and grain translocation efficiency, the inclusion of these Zn-efficient genotypes in breeding programs, and Zn fertilization through soil, foliar and seed treatments.

     

旱地小麦理想株型与生长冗余

自1968年Donald提出作物理想株型(ideotype)以来,众多学者在如何减少生长冗余、塑造理想株型方面做了大量努力,在旱地小麦育种策略和栽培管理模式创新方面取得了一定进展。而该方面的进展有限,不同领域的研究者对理想株型和生长冗余的认识存在严重分歧。综述了近年来旱地小麦理想株型研究进展,以过去20年黄土高原雨养农业区的观测数据为主进行了集成分析,将产量分别与根系生物量、地上生物量和株高等指标进行回归分析,勾画了旱地小麦在根系、茎秆和分蘖等器官中生长冗余的演变趋势,对生长冗余产生的生态学机制展开了分析,并对理想株型与生长冗余的互作关系进行了讨论。已有的研究进展表明,旱地小麦理想株型演变是一个不断消减生长冗余,但又无法完全消除冗余的复杂过程,一定程度的冗余存在是理想株型发生的物质基础。旱地小麦理想株型育种必须以基因型和环境互作关系为基础,通过减少个体间的竞争强度和个体大小不整齐性,促进物质和能量更多地向籽粒迁移,最终提高种群产量。综上所述,旱地小麦理想株型选择需建立在生长冗余理论基础上,根据生态学基本原理对基因型和表现型进行耦合分析与选择权衡。     

Unlocking the diversity of genebanks: whole-genome marker analysis of Swiss bread wheat and spelt

Key message

High-throughput genotyping of Swiss bread wheat and spelt accessions revealed differences in their gene pools and identified bread wheat landraces that were not used in breeding.

Abstract

Genebanks play a pivotal role in preserving the genetic diversity present among old landraces and wild progenitors of modern crops and they represent sources of agriculturally important genes that were lost during domestication and in modern breeding. However, undesirable genes that negatively affect crop performance are often co-introduced when landraces and wild crop progenitors are crossed with elite cultivars, which often limit the use of genebank material in modern breeding programs. A detailed genetic characterization is an important prerequisite to solve this problem and to make genebank material more accessible to breeding. Here, we genotyped 502 bread wheat and 293 spelt accessions held in the Swiss National Genebank using a 15K wheat SNP array. The material included both spring and winter wheats and consisted of old landraces and modern cultivars. Genome- and sub-genome-wide analyses revealed that spelt and bread wheat form two distinct gene pools. In addition, we identified bread wheat landraces that were genetically distinct from modern cultivars. Such accessions were possibly missed in the early Swiss wheat breeding program and are promising targets for the identification of novel genes. The genetic information obtained in this study is appropriate to perform genome-wide association studies, which will facilitate the identification and transfer of agriculturally important genes from the genebank into modern cultivars through marker-assisted selection.

     

单克隆抗体技术在小麦贮藏蛋白研究及其遗传改良中的应用进展

近20年来,人们制备了许多小麦种子贮藏蛋白的单克隆抗体(Monoclonal Antibody,McAb),一方面作为有效工具研究胚乳贮藏蛋白(主要是麦谷蛋白聚集体、特定的谷蛋白亚基及醇溶蛋白)的结构与功能关系;另一方面用作诊断试剂(diagnostic tools),为筛选具有合适加工品质的小麦品种提供依据。本文综述了国内外单克隆抗体技术在小麦贮藏蛋白研究及其遗传改良中的应用进展,并展望其应用前景。     

Phenology and related traits for wheat adaptation

Wheat is a major food crop, with around 765 million tonnes produced globally. The largest wheat producers include the European Union, China, India, Russia, United States, Canada, Pakistan, Australia, Ukraine and Argentina. Cultivation of wheat across such diverse global environments with variation in climate, biotic and abiotic stresses, requires cultivars adapted to a range of growing conditions. One intrinsic way that wheat achieves adaptation is through variation in phenology (seasonal timing of the lifecycle) and related traits (e.g., those affecting plant architecture). It is important to understand the genes that underlie this variation, and how they interact with each other, other traits and the growing environment. This review summarises the current understanding of phenology and developmental traits that adapt wheat to different environments. Examples are provided to illustrate how different combinations of alleles can facilitate breeding of wheat varieties with optimal crop performance for different growing regions or farming systems.Subject terms: Shoot apical meristem, Agricultural genetics, Plant breeding     

Sequence-based marker development in wheat: advances and applications to breeding

In the past two decades, the wheat community has made remarkable progress in developing molecular resources for breeding. A wide variety of molecular tools has been established to accelerate genetic and physical mapping for facilitating the efficient identification of molecular markers linked to genes and QTL of agronomic interest. Already, wheat breeders are benefiting from a wide range of techniques to follow the introgression of the most favorable alleles in elite material and develop improved varieties. Breeders soon will be able to take advantage of new technological developments based on Next Generation Sequencing. In this paper, we review the molecular toolbox available to wheat scientists and breeders for performing fundamental genomic studies and breeding. Special emphasis is given on the production and detection of single nucleotide polymorphisms (SNPs) that should enable a step change in saturating the wheat genome for more efficient genetic studies and for the development of new selection methods. The perspectives offered by the access to an ordered full genome sequence for further marker development and enhanced precision breeding is also discussed. Finally, we discuss the advantages and limitations of marker-assisted selection for supporting wheat improvement.     

Genetic engineering of wheat--current challenges and opportunities

Wheat is one of the major staple food crops grown worldwide; however, productivity in cereal crops has not kept pace with the world population growth. A significant increase in wheat production (>40% by 2020) is needed simply to keep up with the growing demand. This increase is unlikely to be achieved by conventional plant breeding methods because of the limited gene pool available. The application of recombinant techniques to improve wheat quality and yield is not only desirable but also has potential to open up new opportunities. Although there has been significant progress in developing gene-transformation technologies for improving these traits, this remains an important challenge for plant biotechnology. Obstacles to translate the full potential of the genomic era to wheat breeding include the need to develop elite wheat varieties without selectable markers, introducing minimal or nil intergenic DNA and social and market issues concerning genetically engineered food products.     

植物细胞工程在小麦抗赤霉病育种中的应用

小麦赤霉病是全球性小麦病害,严重影响小麦产量和品质,赤霉菌产生的毒素进一步威胁人畜安全,培育抗病品种是控制小麦赤霉病危害的根本途径。植物细胞工程技术可创造新的遗传变异、加快育种进程,已经广泛应用于小麦抗赤霉病育种。概述了体细胞无性系变异诱导、花药培养、小麦与玉米杂交培育加倍单倍体以及幼胚培养一年多代快速成苗等植物细胞工程技术研究进展,着重介绍了其在抗小麦赤霉病育种中的应用。最后对未来发展趋势做了展望,植物细胞工程结合分子育种技术将在小麦抗赤霉病品种培育中发挥更重要的作用。     

Will genomic selection be a practical method for plant breeding?

Background

Genomic selection or genome-wide selection (GS) has been highlighted as a new approach for marker-assisted selection (MAS) in recent years. GS is a form of MAS that selects favourable individuals based on genomic estimated breeding values. Previous studies have suggested the utility of GS, especially for capturing small-effect quantitative trait loci, but GS has not become a popular methodology in the field of plant breeding, possibly because there is insufficient information available on GS for practical use.

Scope

In this review, GS is discussed from a practical breeding viewpoint. Statistical approaches employed in GS are briefly described, before the recent progress in GS studies is surveyed. GS practices in plant breeding are then reviewed before future prospects are discussed.

Conclusions

Statistical concepts used in GS are discussed with genetic models and variance decomposition, heritability, breeding value and linear model. Recent progress in GS studies is reviewed with a focus on empirical studies. For the practice of GS in plant breeding, several specific points are discussed including linkage disequilibrium, feature of populations and genotyped markers and breeding scheme. Currently, GS is not perfect, but it is a potent, attractive and valuable approach for plant breeding. This method will be integrated into many practical breeding programmes in the near future with further advances and the maturing of its theory.Key words: Genomic selection, plant breeding, marker assisted selection, genetic model, linkage disequilibrium     

Chromosome changes after polyploidization in Triticeae

Chromosome changes are common in Triticeae, and they occur widely in natural and resynthesized polyploidy. Two important factors, nucleocytoplasmic interaction (internal) and the environment (external), can significantly influence chromosome changes after polyploidization. And chromosomal DNA changes play key roles during the initial formation, gradual stabilization, and establishment of polyploids. Hybrid breeding between common wheat and related wild species of Triticeae is an example of polyploidization, and many of the chromosome changes occurring after hybridization could be useful for improving wheat varieties. The famous chromosomal translocation 1BL/1RS that occurred after ancestral hybridization between wheat and rye is distributed widely among modern wheat varieties and makes a big contribution to wheat breeding; xiaoyan 6 is a similarly distant hybridization between wheat and Agropyron elongatum (Host) P. Beauv. in China. This chromosome translocation line was cultivated as the main variety in Shaanxi Province for 16 years and has also been used as a core parent for wheat breeding in China during the past 20 years because of its outstanding merits.     

Synthetic hexaploid wheat enhances variation and adaptive evolution of bread wheat in breeding processes

Synthetic hexaploid wheat (SHW) that combines novel and elite genes from the tetraploid wheat Triticum turgidum L. and wild ancestor Aegilops tauschii Coss., has been used to genetically improve hexaploid common wheat. The abundant genetic diversity in SHW can effectively make breakthroughs in wheat genetic improvement through the inclusion of increased variation. In this paper, we reviewed the current advances in research and utilization of the primary SHW lines and SHW-derived wheat varieties that have enhanced evolution of modern wheat under conditions of natural and artificial selection in southwestern China. Using primary SHW lines, four high-yielding wheat varieties have been developed. In addition, using the SHW-derived varieties as breeding parents, 12 new wheat varieties were also developed. Results of genotype–phenotype and fingerprint analysis showed that the introgressed alleles from SHW lines have contributed a great number of elite characters to the new wheat varieties, and these elite characters include disease resistance, more spikes per plant, more grains per spike, larger grains, and higher grain-yield potential. We found that the primary SHW lines and SHW-derived varieties have identifiable effects to enhance genetic variation and adaptive evolution of modern hexaploid wheat, which significantly increased the grain yields of hexaploid wheat in recent years. These findings have significant implications in the breeding of high-yielding wheat varieties resistant to biotic and abiotic stresses using SHW as genetic resources.     

花卉分子育种的研究进展

介绍花卉分子育种的研究概况和分子育种的操作策略。进一步强调在我国应用和发展花卉分子育种方法的必要性。     

小麦高分子量麦谷蛋白亚基鉴定及其品质效应研究进展

高分子量谷蛋白亚基(HMW-GS,high molecular weight glutenin subunits)是小麦子粒贮藏蛋白的重要组成成分,其组成、搭配、表达水平及含量决定面团弹性和面包加工品质。本文主要介绍了小麦HMW-GS编码基因的克隆、分子特征、分子标记开发及其在小麦育种中的应用,并综述了不同HMW-GS与面粉加工品质之间的关系,以及HMW-GS基因遗传转化、微量配粉和突变体培育等方面的研究进展,分析了目前研究中存在的主要问题,认为通过分子标记辅助选择和转基因技术聚合优质亚基,培育优质面包小麦品种和明确各个HMW-GS基因的品质效应是今后的研究重点。