Abstract Increasing population and consumption are placing unprecedented demands on agriculture and natural resources. Today, approximately a billion people are chronically malnourished while our agricultural systems are concurrently degrading land, water, biodiversity and climate on a global scale. To meet the world's future food security and sustainability needs, food production must grow substantially while, at the same time, agriculture's environmental footprint must shrink dramatically. Here we analyse solutions to this dilemma, showing that tremendous progress could be made by halting agricultural expansion, closing 'yield gaps' on underperforming lands, increasing cropping efficiency, shifting diets and reducing waste. Together, these strategies could double food production while greatly reducing the environmental impacts of agriculture.

Borthwick HA, Cathey HM.

Photoperiodic changes, if occurring before a commitment to flowering is established, can alter the morphological pattern of plant development. In this study, Glycine max (L.) Merrill cv. Ransom plants were initially grown under an inductive short-day (SD) photoperiod to promote flower evocation and then transferred to a long-day (LD) photoperiod to delay flower development by reestablishing vegetative growth (SD-LD plants). Some plants were transferred back to SD after 4-LD exposures to repromote flowering (SD-LD-SD plants). Alterations in organ initiation patterns, from floral to vegetative and back to floral, are characteristic of a reversion phenomenon. Morphological features that occurred at the shoot apical meristem in SD, LD, SD-LD, and SD-LD-SD plants were observed using scanning electron microscopy (SEM). Reverted plants initiated floral bracts and resumed initiation of trifoliolate leaves in the two-fifths floral phyllotaxy prior to terminal inflorescence development. When these plants matured, leaf-bract intermediates were positioned on the main stem instead of trifoliolate leaves. Plants transferred back to a SD photoperiod flowered earlier than those left in LD conditions. Results indicated that in plants transferred between SDs and LDs, photoperiod can influence organ initiation in florally evoked, but not committed, G. max plants.

利用中国大豆主要生态区的生育期不同的代表品种研究了大豆（Ｇｌｙｃｉｎｅ ｍ ａｘ （Ｌ．）Ｍｅｒｒ．）开花后对光照长度的反应． 结果表明，不同成熟期的大豆品种开花后普遍存在着对光照长度的反应．这种反应属于典型的光周期现象，而不是由温度的替代作用、光合时间的改变或前期短日后效应引起的．开花后光周期反应不仅存在于大豆的花荚期，而且存在于鼓粒期．研究认为∶大豆开花结实对光周期的需求是一个连续过程；光周期对大豆生育期的调控作用存在于出苗至成熟的全过程；光周期诱导开花和促进成熟的作用有一定的共同性；光周期诱导效果具有持效性和可逆性

选用来自中国不同大豆生态区的15个代表品种,比较了不同产地、不同生育期、不同播期类型的大豆品种开花后光周期反应的差异。结果表明,大豆品种在开花后光周期反应方面存在着广泛的遗传多样性。中国大豆典型生态类型开花后光周期反应敏感性有以下顺序:南方秋豆南方夏豆黄淮夏豆南方春豆、黄淮春豆北方春豆。试验中发现,大豆品种开花至成熟期各阶段长度与它们在自然条件下出苗至初花(R1)的日数正相关。供试的早熟品种开花后对光周期的反应比开花前更加敏感。

在人工控制条件下,研究了开花后的光照长度对大豆农艺性状的影响及大豆不同发育阶段长度与农艺性状的相关性.结果表明,开花后长日照可提高大豆的干物质积累量,在正常成熟的前提下可明显提高产量.试验进一步证明鼓粒期长度与粒重和产量呈正相关,花荚期长度对产量形成相当重要.认为东北大豆花荚期及以前的长日照有助于干物质的积累和较多花荚数量的形成,鼓粒开始后迅速缩短的日照条件可促进干物质向籽粒的运转,并加快籽粒的整齐成熟.

http://www.annualreviews.org/doi/abs/10.1146/annurev.pp.04.060153.002023

<p><span style="font-size: 9pt">设置短日照</span><span style="font-size: 9pt">(</span><span style="font-size: 9pt">12 h</span><span style="font-size: 9pt">)</span><span style="font-size: 9pt">和长日照</span><span style="font-size: 9pt">(</span><span style="font-size: 9pt">16 h</span><span style="font-size: 9pt">)</span><span style="font-size: 9pt">两种光周期处理，并以春播模拟低温、夏播模拟高温条件，形成长日</span><span style="font-size: 9pt">+</span><span style="font-size: 9pt">低温、长日</span><span style="font-size: 9pt">+</span><span style="font-size: 9pt">高温、短日</span><span style="font-size: 9pt">+</span><span style="font-size: 9pt">低温、短日</span><span style="font-size: 9pt">+</span><span style="font-size: 9pt">高温</span><span style="font-size: 9pt">4</span><span style="font-size: 9pt">种光温组合。</span><span style="font-size: 9pt">2007</span><span style="font-size: 9pt">年对近年育成的</span><span style="font-size: 9pt">10</span><span style="font-size: 9pt">个北方春大豆</span><span style="font-size: 9pt">[<em>Glycine max</em> (L.) Merr.]</span><span style="font-size: 9pt">品种</span><span style="font-size: 9pt">(</span><span style="font-size: 9pt">系</span><span style="font-size: 9pt">)</span><span style="font-size: 9pt">和</span><span style="font-size: 9pt">18</span><span style="font-size: 9pt">个黄淮海夏大豆品种</span><span style="font-size: 9pt">(</span><span style="font-size: 9pt">系</span><span style="font-size: 9pt">)</span><span style="font-size: 9pt">进行了光温反应特性鉴定。</span><span style="font-size: 9pt">2008</span><span style="font-size: 9pt">年对</span><span style="font-size: 9pt">50</span><span style="font-size: 9pt">份材料进行了光周期反应鉴定。结果表明，不论在低温</span><span style="font-size: 9pt">(</span><span style="font-size: 9pt">春播</span><span style="font-size: 9pt">)</span><span style="font-size: 9pt">还是高温</span><span style="font-size: 9pt">(</span><span style="font-size: 9pt">夏播</span><span style="font-size: 9pt">)</span><span style="font-size: 9pt">条件下，短日照均加快大豆的发育进程，导致开花提前；不论在长日照还是短日照条件下，高温均减少出苗至初花的日数。光周期和温度对大豆的发育存在明显的互作，随着温度的升高，短日照促进大豆发育的效应有所加强；随着日照的缩短，高温加快发育的作用也有所增大。供试大豆品种生态类型在光周期反应敏感度</span><span style="font-size: 9pt">(</span><span style="font-size: 9pt">PRS</span><span style="font-size: 9pt">)</span><span style="font-size: 9pt">、温度反应敏感度</span><span style="font-size: 9pt">(</span><span style="font-size: 9pt">TRS</span><span style="font-size: 9pt">)</span><span style="font-size: 9pt">及光温综合反应敏感度</span><span style="font-size: 9pt">(</span><span style="font-size: 9pt">PTCRS</span><span style="font-size: 9pt">)</span><span style="font-size: 9pt">等方面均存在显著差异。北方春大豆品种的上述</span><span style="font-size: 9pt">3</span><span style="font-size: 9pt">个指标均小于黄淮海夏大豆品种，但前者在不同光照条件下的温度反应敏感度差值和在不同温度条件下的光周期反应敏感度差值均较后者高，说明北方春大豆品种光温互作效应较强。</span></p>

Soybean (Glycine max(L.) Merr.) is a short day plant. Its flowering and maturity time are controlled by genetic and environmental factors, as well the interaction between the two factors. Previous studies have shown that both genetic and environmental factors, mainly photoperiod and temperature, control flowering time of soybean. Additionally, these studies have reported gene65×65gene and gene65×65environment interactions on flowering time. However, the effects of quantitative trait loci (QTL) in response to photoperiod and temperature have not been well evaluated. The objectives of the current study were to identify the effects of loci associated with flowering time under different photo-thermal conditions and to understand the effects of interaction between loci and environment on soybean flowering. Different photoperiod and temperature combinations were obtained by adjusting sowing dates (spring sowing and summer sowing) or day-length (1202h, 1602h). Association mapping was performed on 91 soybean cultivars from different maturity groups (MG000-VIII) using 172 SSR markers and 5107 SNPs from the Illumina SoySNP6K iSelectBeadChip. The effects of the interaction between QTL and environments on flowering time were also analysed using the QTXNetwork. Large-effect loci were detected on Gm 11, Gm 16 and Gm 20 as in previous reports. Most loci associated with flowering time are sensitive to photo-thermal conditions. Number of loci associated with flowering time was more under the long day (LD) than under the short day (SD) condition. The variation of flowering time among the soybean cultivars mostly resulted from the epistasis65×65environment and additive65×65environment interactions. Among the three candidate loci, i.e. Gm04_4497001 (nearGmCOL3a), Gm16_30766209 (nearGmFT2aandGmFT2b) and Gm19_47514601 (E3orGmPhyA3), the Gm04_4497001 may be the key locus interacting with other loci for controlling soybean flowering time. The effects of loci associated with the flowering time of soybean were dependent upon the photo-thermal conditions. This study facilitates the understanding of the genetic mechanism of soybean flowering and molecular breeding for the improvement of soybean adaptability to specific and/or broad regions. The online version of this article (doi:10.1186/s12864-017-3778-3) contains supplementary material, which is available to authorized users.

Analysis of genes controlling flowering time (heading date) contributes to our understanding of fundamental principles of plant development and is of practical importance because of the effects of flowering time on plant adaptation and crop yield. This review discusses the extent to which plants may share common genetic mechanisms for the control of flowering time and the implications of such conservation for gene isolation from the major cereal crops. Gene isolation may exploit the small genome of rice in map-based approaches, utilizing the conservation of gene order that is revealed when common DNA markers are mapped in different species. Alternatively, mechanisms may be conserved within plants as a whole, in which case genes cloned from the model dicot Arabidopsis thaliana provide an alternative route.

Arabidopsis flowers early under long days (LD) and late under short days (SD). The repressor of photomorphogenesis DE-ETIOLATED1 (DET1) delays flowering; det1-1 mutants flower early, especially under SD, but the molecular mechanism of DET1 regulation remains unknown. Here we examine the regulatory function of DET1 in repression of flowering. Under SD, the det1-1 mutation causes daytime expression of FKF1 and CO; however, their altered expression has only a small effect on early flowering in det1-1 mutants. Notably, DET1 interacts with GI and binding of GI to the FT promoter increases in det1-1 mutants, suggesting that DET1 mainly restricts GI function, directly promoting FT expression independent of CO expression. Moreover, DET1 interacts with MSI4/FVE, which epigenetically inhibits FLC expression, indicating that the lack of FLC expression in det1-1 mutants likely involves altered histone modifications at the FLC locus. These data demonstrate that DET1 acts in both photoperiod and autonomous pathways to inhibit expression of FT and SOC1. Consistent with this, the early flowering of det1-1 mutants disappears completely in the ft-1 soc1-2 double mutant background. Thus, we propose that DET1 is a strong repressor of flowering and has a pivotal role in maintaining photoperiod sensitivity in the regulation of flowering time.

Abstract One mechanism through which flowering in response to seasonal change is brought about is by sensing the fluctuation in day-length; the photoperiod. Flowering induction occurs through the production of the florigenic protein FLOWERING LOCUS T (FT) and its movement from the phloem companion cells in the leaf vasculature into the shoot apex, where meristematic reprogramming occurs. FT activation in response to photoperiod condition is accomplished largely through the activity of the transcription factor CONSTANS (CO). Regulation of CO expression and protein stability, as well as the timing of other components via the circadian clock, is a critical mechanism by which plants are able to respond to photoperiod to initiate the floral transition. Modulation of FT expression in response to external and internal stimuli via components of the flowering network is crucial to mediate a fluid flowering response to a variety of environmental parameters. In addition, the regulated movement of FT protein from the phloem to the shoot apex, and interactions that determine floral meristem cell fate, constitute novel mechanisms through which photoperiodic information is translated into flowering time.

Most of the genes of an organism are known from sequence, but most of the phenotypes are obscure. Thus, reverse genetics has become an important goal for many biologists. However, reverse-genetic methodologies are not similarly applicable to all organisms. In the general strategy for reverse genetics that we call TILLING (for Targeting Induced Local Lesions in Genomes), traditional chemical mutagenesis is followed by high-throughput screening for point mutations. TILLING promises to be generally applicable. Furthermore, because TILLING does not involve transgenic modifications, it is attractive not only for functional genomics but also for agricultural applications. Here, we present an overview of the status of TILLING methodology, including Ecotilling, which entails detection of natural variation. We describe public TILLING efforts in Arabidopsis and other organisms, including maize (Zea mays) and zebrafish. We conclude that TILLING, a technology developed in plants, is rapidly being adopted in other systems.

The circadian clock allows plants to anticipate and respond to daily changes in ambient temperature. Mechanisms establishing the timing of circadian rhythms in Arabidopsis thaliana through temperature entrainment remain unclear. Also incompletely understood is the temperature compensation mechanism that maintains consistent period length within a range of ambient temperatures. A genetic screen for Arabidopsis mutants affecting temperature regulation of the PSEUDO-RESPONSE REGULATOR7 promoter yielded a novel allele of the SICKLE (SIC) gene. This mutant, sic-3, and the existing sic-1 mutant both exhibit low-amplitude or arrhythmic expression of core circadian clock genes under cool ambient temperature cycles, but not under light-dark entrainment. sic mutants also lengthen free running period in a manner consistent with impaired temperature compensation. sic mutant alleles accumulate LATE ELONGATED HYPOCOTYL (LHY) and CIRCADIAN CLOCK ASSOCIATED1 (CCA1) splice variants, among other alternatively spliced transcripts, which is exacerbated by cool temperatures. The cca1-1 lhy-20 double mutant is epistatic to sic-3, indicating the LHY and CCA1 splice variants are needed for sic-3 circadian clock phenotypes. It is not expected that SIC is directly involved in the circadian clock mechanism; instead, SIC likely contributes to pre-mRNA metabolism, and the splice variants that accumulate in sic mutants likely affect the circadian clock response to cool ambient temperature.

The circadian clock is required for adaptive responses to daily and seasonal changes in environmental conditions1-3. Light and the circadian clock interact to consolidate the phase of hypocotyl cell elongation to dawn under diurnal cycles inArabidopsis thaliana4-7. Here we identify a protein complex (Evening Complex) composed ofEARLY FLOWERING 3 (ELF3), EARLY FLOWERING 4 (ELF4)and the transcription factorLUX ARRHYTHMO (LUX)that directly regulates plant growth8-12. ELF3 is both necessary and sufficient to form a complex between ELF4 and LUX, and the complex is diurnally regulated, peaking at dusk.ELF3, ELF4andLUXare required for the proper expression of the growth-promoting transcription factorsPHYTOCHROME-INTERACTING FACTOR 4 (PIF4)andPIF5under diurnal conditions4,6,13. LUX targets the complex to the promoters ofPIF4andPIF5 in vivo. Mutations inPIF4and/orPIF5are epistatic to the loss of the ELF4-ELF3-LUX complex, suggesting that regulation ofPIF4andPIF5is a critical function of the complex. Therefore, the Evening Complex underlies the molecular basis for circadian gating of hypocotyl growth in the early evening.

Arabidopsis GIGANTEA (GI) is encoded by a single gene and highly conserved among vascular plants and its mutants display pleiotropic phenotypes involved in diverse biological processes such as light signaling, circadian clock, and sucrose metabolism as well as abiotic stress responses. However, molecular mechanisms of GI are largely unknown due to the lack of useful antibody. To date, the epitope tags have been widely used to detect GI in plants, but it needs to generate the transgenic plants which take a few months. Here, we produced polyclonal α-GI antibody using truncated variants of GI having amino-terminal (1–858 aa) and carboxyl-terminal (920–1173) regions as antigens. Both recombinant His-GI 1-858 and His-GI 920–1173 proteins were individually and successfully expressed in E. coli and immunized into rabbit. Anti-serum was purified by antigenspecific affinity purification method using both recombinant His-GI 1–858 and His-GI 920–1173 proteins. Purified polyclonal α-GI antibody not only detected endogenous GI proteins in wild-type Arabidopsis plants, but also reenacted its diel oscillations. Furthermore, the antibody showed cross-reactivity with the GI orthologs in other plants such as Chinese cabbage, rape and tomato. Our polyclonal GI antibody could help to determine the molecular mechanisms of GI involved in largely unknown pleiotropic responses in plants.

Abstract Current understanding of the epigenetic regulator roles in plant growth and development has largely derived from studies in the dicotyledonous model plant Arabidopsis thaliana. Rice (Oryza sativa) is one of the most important food crops in the world and has more recently becoming a monocotyledonous model plant in functional genomics research. During the past few years, an increasing number of studies have reported the impact of DNA methylation, non-coding RNAs and histone modifications on transcription regulation, flowering time control, and reproduction in rice. Here, we review these studies to provide an updated complete view about chromatin modifiers characterized in rice and in particular on their roles in epigenetic regulation of flowering time, reproduction, and seed development.

Summary Soybean flowering and maturation are strictly regulated by photoperiod. Photoperiod-sensitive soybean varieties can undergo flowering reversion when switched from short-day (SD) to long-day (LD) conditions, suggesting the presence of a loral-inhibitor under LD conditions. We combined gene expression profiling with a study of transgenic plants and confirmed that GmFT1a , soybean Flowering Locus T ( FT ) homolog, is a floral inhibitor. GmFT1a is expressed specifically in leaves, similar to the flowering-promoting FT homologs GmFT2a/5a . However, in Zigongdongdou (ZGDD), a model variety for studying flowering reversion, GmFT1a expression was induced by LD but inhibited by SD conditions. This was unexpected, as it is the complete opposite of the expression of flowering promoters GmFT2a/5a . Moreover, the key soybean maturity gene E1 may up-regulate GmFT1a expression. It is also notable that GmFT1a expression was conspicuously high in late-flowering varieties. Transgenic overexpression of GmFT1a delayed flowering and maturation in soybean, confirming that GmFT1a functions as a flowering inhibitor. This discovery highlights the complex impacts of the functional diversification of the FT gene family in soybean, and implies that antagonism between flowering-inhibiting and flowering-promoting FT homologs in this highly photoperiod-sensitive plant may specify vegetative vs reproductive development.

Plants do not bloom randomly--but how do they know when and where to make flowers? Here, we review molecular mechanisms that integrate spatial and temporal information in day-length-dependent flowering. Primarily through genetic analyses in two species, Arabidopsis thaliana and rice, we today understand the essentials of two central issues in plant biology: how the appropriate photoperiod generates an inductive stimulus based on an external coincidence mechanism, and the nature of the mobile flowering signal, florigen, which relays photoperiod-dependent information from the leaf to the growing tip of the plant, the shoot apex.

Abstract Plants undergo a major physiological change as they transition from vegetative growth to reproductive development. This transition is a result of responses to various endogenous and exogenous signals that later integrate to result in flowering. Five genetically defined pathways have been identified that control flowering. The vernalization pathway refers to the acceleration of flowering on exposure to a long period of cold. The photoperiod pathway refers to regulation of flowering in response to day length and quality of light perceived. The gibberellin pathway refers to the requirement of gibberellic acid for normal flowering patterns. The autonomous pathway refers to endogenous regulators that are independent of the photoperiod and gibberellin pathways. Most recently, an endogenous pathway that adds plant age to the control of flowering time has been described. The molecular mechanisms of these pathways have been studied extensively in Arabidopsis thaliana and several other flowering plants.

Abstract The wheat florigen gene Wheat FLOWERING LOCUS T (WFT, which is identical to VRN3) is an integrator of the vernalization, photoperiod and autonomous pathways in wheat flowering. Many studies have indicated that VERNALIZATION 1 (VRN1) directly or indirectly up-regulates WFT expression in leaves. VRN1 encodes an APETALA1/FRUITFULL-like MADS-box transcription factor that is up-regulated by vernalization and aging, leading to promotion of flowering. In this study, the VRN1 protein was expressed as a His-Tag fusion protein in Escherichia coli and used in an electrophoretic mobility shift assay (EMSA). The results from the EMSA indicated that the VRN1 protein directly binds to the CArG-box in the promoter region of WFT, suggesting the direct up-regulation of WFT by VRN1 in the leaves of wheat plants.

ABSTRACT Flowering of many plant species is coordinated with seasonal environmental cues such as temperature and photoperiod. Vernalization provides competence to flower after prolonged cold exposure, and a vernalization requirement prevents flowering from occurring prior to winter. In winter wheat and barley, three genes VRN1, VRN2, and FT form a regulatory loop that regulates the initiation of flowering. Prior to cold exposure, VRN2 represses FT. During cold, VRN1 expression increases, resulting in the repression of VRN2, which in turn allows activation of FT during long days to induce flowering. Here we test whether the circuitry of this regulatory loop is conserved across Pooideae,consistent with their niche transition from the tropics to the temperate zone. Our phylogenetic analyses of VRN2-like genes reveal a duplication event occurred before the diversification of the grasses that gave rise to a CO9 and VRN2/GhD7 clade, and supports orthology between wheat/barley VRN2 and rice GhD7. Our Brachypodium distachyon VRN1 and VRN2 knockdown and overexpression experiments demonstrate functional conservation of grass VRN1 and VRN2 in the promotion and repression of flowering, respectively. However, expression analyses in a range of pooids demonstrate that the cold repression of VRN2 is unique to core Pooideae such as wheat and barley. Furthermore, VRN1 knock down in Brachypodium demonstrates that the VRN1 mediated suppression of VRN2 is not conserved. Thus, the VRN1-VRN2 feature of the regulatory loop appears to have evolved late in the diversification of temperate grasses.

Mutants of Arabidopsis thaliana deficient in gibberellin synthesis (ga1-3 and ga1-6), and a gibberellin-insensitive mutant (gai) were compared to the wild-type (WT) Landsberg erecta line for flowering time and leaf number when grown in either short days (SD) or continuous light (CL). The ga1-3 mutant, which is severely defective in ent-kaurene synthesis because it lacks most of the GA1 gene, never flowered in SD unless treated with exogenous gibberellin. After a prolonged period of vegetative growth, this mutant eventually underwent senescence without having produced flower buds. The gai mutant and the "leaky" ga1-6 mutant did flower in SD, but took somewhat longer than WT. All the mutants flowered readily in CL, although the ga1-3 mutant showed some delay. Unlike WT and ga1-3, the gai mutant failed to respond to gibberellin treatment by accelerating flowering in SD. A cold treatment promoted flowering in the WT and gai, but failed to induce flowering in ga1-3. From these results, it appears that gibberellin normally plays a role in initiating flowering of Arabidopsis.

Summary Gibberellins (GAs) play a critical role in fruit-set and fruit growth. Gibberellin is perceived by its nuclear receptors GA INSENSITIVE DWARF1s (GID1s), which then trigger degradation of downstream repressors DELLAs. To understand the role of the three GA receptor genes ( GID1A , GID1B and GID1C ) in Arabidopsis during fruit initiation, we have examined their temporal and spatial localization, in combination with analysis of mutant phenotypes. Distinct expression patterns are revealed for each GID1: GID1A is expressed throughout the whole pistil, while GID1B is expressed in ovules, and GID1C is expressed in valves. Functional study of gid1 mutant combinations confirms that GID1A plays a major role during fruit-set and growth, whereas GID1B and GID1C have specific roles in seed development and pod elongation, respectively. Therefore, in ovules, GA perception is mediated by GID1A and GID1B, while GID1A and GID1C are involved in GA perception in valves. To identify tissue-specific interactions between GID1s and DELLAs, we analyzed spatial expression patterns of four DELLA genes that have a role in fruit initiation ( GAI , RGA , RGL1 and RGL2 ). Our data suggest that GID1A can interact with RGA and GAI in all tissues, whereas GID1C–RGL1 and GID1B–RGL2 interactions only occur in valves and ovules, respectively. These results uncover specific functions of each GID1–DELLA in the different GA-dependent processes that occur upon fruit-set. In addition, the distribution of GA receptors in valves along with lack of expression of GA biosynthesis genes in this tissue, strongly suggests transport of GAs from the developing seeds to promote fruit growth.

Signals produced in leaves are transported to the shoot apex where they cause flowering. Protein of the gene FLOWERING LOCUS T (FT) is probably a long day (LD) signal in Arabidopsis. In the companion paper, rapid LD increases in FT expression associated with flowering driven photosynthetically in red light were documented. In a far red (FR)-rich LD, along with FT there was a potential role for gibberellin (GA). Here, with the GA biosynthesis dwarf mutant ga1-3, GA4-treated plants flowered after 26 d in short days (SD) but untreated plants were still vegetative after 6 months. Not only was FT expression low in SD but applied GA bypassed some of the block to flowering in ft-1. On transfer to LD, ga1-3 only flowered when treated simultaneously with GA, and FT expression increased rapidly (<19.5 h) and dramatically (15-fold). In contrast, in the wild type in LD there was little requirement for GA for FT increase and flowering so its endogenous GA content was near to saturating. Despite this permissive role for endogenous GA in Columbia, RNA interference (RNAi) silencing of the GA biosynthesis gene, GA 20-OXIDASE2, revealed an additional, direct role for GA in LD. Flowering took twice as long after silencing the LD-regulated gene, GA 20-OXIDASE2. Such independent LD input by FT and GA reflects their non-sympatric expression (FT in the leaf blade and GA 20-OXIDASE2 in the petiole). Overall, FT acts as the main LD floral signal in Columbia and GA acts on flowering both via and independently of FT.

No Abstract available for this article.

正 一、前言玉米是高产作物,又是饲料之王。由于玉米的自交系间杂交种较之品种间杂交更能增产,所以中央农业部在历次全国玉米会议上都指示我国玉米工作者,要在玉米品种间杂交种的基础上,开展自交系间杂交种的研究,研制和推广到生产上应用,以获得更高的玉米单位面积的产量。但在

海南南繁制种水稻已有40多年的历史,从20世纪90年代以来,制种面积每年在10万亩左右,今年达到12万亩,约占全国南繁制种总面积的90%,南繁制种面积累计达120多万亩,为保障国家粮食安全做出了突出贡献。在水稻种子生产过程中南繁水稻制种是很重要的一个环节,基本上是由独立且相对固定的生产群体进行订单式生产,由于生产者的特殊性以及一些外部环境的原因,南繁制种水稻基地也因此出现了问题。这些问题如果不能很好地加以分析和解决,我国制种产业乃至整个种业链条都会受到影响。本文通过对南繁制种水稻基地的实地调研,对目前的基地现状及进行分析,并且提出改善的建议。

International wheat breeding began 60 years ago in the Mexican-Rockefeller Foundation Office of Special Studies. A novel technique of shuttle breeding was adopted in Mexico, enabling photoperiod sensitivity to be overcome, a pivotal step in creating internationally adapted spring wheat germplasm that eventually spread throughout the world. The high-yielding technologies developed in Mexico helped revolutionize cereal production during the 1960s and 1970s, and came to be known as the “Green Revolution.” In the process, a highly effective system of international agricultural research centers evolved under the umbrella of the Consultative Group for International Agriculture (CGIAR). This international system has weakened in recent decades, despite the enormous challenges facing humankind to expand food production in environmentally sustainable ways. Biotechnology holds great promise to develop improved crop varieties to deal with new pests and diseases, drought, and to enhance nutritional content. Those on the food front still have a big job ahead of us to feed the world. There is no room for complacency.

文章以来源于花甜糯072自交后代的糯质玉米为研究对象，于授粉后16，20，24，28，32，36，40 d收获种子，自然晾干至比较一致的含水量后进行活力测定。研究结果表明，该糯质玉米在授粉后32～36 d前后收获种子质量较高。授粉后32 d 收获的种子标准发芽率和顶土萌发率最高，种子浸出液电导率降至最低，后趋于稳定。授粉后36 d的种子千粒重最大，低温发芽率最高。授粉后40 d收获的种子呼吸代谢最强，此时增加代谢时间（IMT）、氧代谢率（OMR）、相对发芽时间（RGT）分别为878 h，386 %&middot;h-1，4256 h，说明此时收获的种子已具备旺盛的呼吸代谢能力。建议糯质玉米种子电导率为41～43 &mu;S&middot;cm-1&middot;g-1，IMT，OMR，RGT值分别为1165～1178 h，286～340 %&middot;h-1，5051～5446 h时采收，可获得高活力种子

1984—1986年在北京进 行早熟、中早熟玉米一年两季加代试验.试验结果表明.第一季加代采用早春(3月上旬—下旬)温室育苗,3月末至4月上旬移栽到塑料薄膜复盖的阳畦、小棚或 大棚;以及3月下旬直播于铺设电热线的阳畦,大棚等增温保温措施,早熟、中早熟玉米自交系和育种材料。可于5月下旬进入抽雄、吐丝、散粉期,7月上旬末以 前收获授粉后25—30天果穗,种子发芽率可达到80%以上,第二季加代采用上季25—30天嫩粒,经2%H_2O_2浸种24小时,于7月上旬播种(气 温偏高年份还可适当延迟播种),在大田条件下,8月下旬可进入抽雄、吐丝、散粉期,授粉工作可进行到9月上旬末,10月底以前收获的种子,发芽率一般达 80%左右,高的达90%以上.H_2O_2处理玉米种子可明显加速种子发芽,促进幼苗生长.采用了短日照处理(8—10小时日照)生育后期叶面喷磷钾肥 和乙烯利等促进早熟措施,对本试验成功实现一年两季加代,均取得了一定效果。

正 我站位于北纬34°04′、东经115°18′的黄淮之间予东平原上,常年无霜期平均为220天。在1976年玉米加代试验的基础上,1978年在不使用温室育苗的条件下,又搞了一年的玉米加代试验。第1代单粒抪种83粒,收获74株,单株结籽451粒,将收获的种子一部分又种在7分土地上,收获玉米种142斤,两代加起来,繁殖系数达13900倍,获得了成功,并初步掌握了一些关键性技术措施.我们认为,凡是中早熟品种,无霜期在210天以上的地区,一年均可就地种植两代。无霜期的不足,是加代中矛盾的主要方

正 为了提高新品种亲本自交系种子的繁殖系数,扩大制种面积,加快良种推广速度,降低成本,提高经济效益,笔者从1976年开始,对稀少的玉米自交系进行就地 一年两季繁殖途径的试验,并于1978—1983年利用就地一年两季繁殖法进行了5个不同气候年度大面积自交系繁殖,均获得成功。实践证明,这种方法栽培 技术容易掌握,操作简单,不需

The growing human population and a changing environment have raised significant concern for global food security, with the current improvement rate of several important crops inadequate to meet future demand [1]. This slow improvement rate is attributed partly to the long generation times of crop plants. Here we present a method called 'speed breeding', which greatly shortens generation time and accelerates breeding and research programs. Speed breeding can be used to achieve up to 6 generations per year for spring wheat (Triticum aestivum), durum wheat (T. durum), barley (Hordeum vulgare), chickpea (Cicer arietinum), and pea (Pisum sativum) and 4 generations for canola (Brassica napus), instead of 2-3 under normal glasshouse conditions. We demonstrate that speed breeding in fully-enclosed controlled-environment growth chambers can accelerate plant development for research purposes, including phenotyping of adult plant traits, mutant studies, and transformation. The use of supplemental lighting in a glasshouse environment allows rapid generation cycling through single seed descent and potential for adaptation to larger-scale crop improvement programs. Cost-saving through LED supplemental lighting is also outlined. We envisage great potential for integrating speed breeding with other modern crop breeding technologies, including high-throughput genotyping, genome editing, and genomic selection, accelerating the rate of crop improvement.

加快作物育种的速度,必须加快相应作物的发育速度。加速植物的发育有2个突破口:1)利用“幼胚培养”省去后面种子发育的时间;2)通过“理化调控”加快植株的发育速度。将“幼胚培养”、“理化调控”结合,便会形成作物的快速发育技术,将快速发育技术与分子标记选择技术结合,便可建立起快速育种或遗传改良的技术。

本所玉米科研人员总结两年试验的经验教训，2004年改进试验方案，不仅完成了玉米就地加代工作，而且还将温室大棚、南繁及夏播相结合，实现了玉米一年繁育三代，从而加速玉米育种进程。

介绍了泰安市玉米自交系一年三代选育模式的概况,包括夏播自交系的选育、冬季海南加代自交系的选育、冬暖式大棚自交系加代等方面内容,以为玉米育种提供参考。

为确立玉米自交系一年三代种植的新模式,采用了温室与大田试验等研究方法,对玉米自交系加代种植与选育技术进行了研究。研究结果表明:玉米自交系山东大棚春播、山东夏播、海南冬繁一年三代种植与选育模式可靠,可操作性强,在不同环境条件下选育自交系扩大了选育范围。利用该加代模式,山东春季大棚2月25日左右播种,5月1日左右授粉,6月12日左右收获,灌浆期42天以上,籽粒基本饱满;夏季6月15日左右播种,10月5日左右收获,及时暴晒考种;海南冬季11月8日左右播种,2月20日左右收获暴晒3天及时运回山东大棚春播,完成一年三代。利用该模式选育出的自交系性状表现可靠,生产上可以利用。

In order to shorten generation cycles, a greenhouse strategy was used as control and compared with an in vitro plus in vivo strategy for pea and bambara groundnut, as well as to an in vitro only strategy for pea and grass pea. Using an in vitro plus in vivo system and embryo axis explants, nearly six generations per year for Pisum and over four generations for Vigna were obtained, compared with two generations in the field. Using successive generations from seed to seed in pea, the mean duration for one generation was 67.2 4.6 days in 'Frisson', against a mean of 143 3 days in the field. With the in vitro only strategy in pea, 6.87 generations per year were obtained with 'Frisson' and 5.24 with 'Terese', while with grass pea genotypes over three generations per year were possible. All plants obtained were morphologically normal and fertile. These results show the feasibility of using such strategies to reduce significantly the duration of generation cycles in legumes, thus offering novel approaches for breeding these important crops.

Generating segregating populations and 'pure lines' is an essential component in many projects of plant breeding and biological studies. Time taken to obtain these materials is often a critical factor restricting the progress of such projects. We report a procedure here which, by combining embryo culture with managements of watering regimes, lighting intensity and duration, temperature and quantity of potting mixture, allows the production of up to eight generations of wheat and nine generations of barley per annum. By dramatically shortening the time frame required to obtain segregating populations and 'pure lines', the procedure could find wide applications in breeding and biological studies.

Abstract In the plant breeding cycle, the length of time from seed to seed is often a limiting factor in producing pure lines or recombinant inbred lines (RILs). The objective of this research was to accelerate the production of field pea RILs while maintaining the population size, through application of a technique referred to as ‘rapid generation technology’ (RGT). The effect of plant hormones and growth conditions were evaluated for two pea cultivars then the optimum combination was applied in the development of RILs from a cross between cultivars CDC Dakota and CDC Amarillo over seven generations. In an average of 33.4 d, 100% of plants flowered when the following conditions were applied in the final in vivo protocol: 0.6 μM flurprimidol, 266 plants per square meter, 20 h photoperiod, 21°C/16°C light/dark, hydroponic system with vermiculite substrate, scheduled fertilizer application, and 500 μM m612 s611 light intensity using T5 fluorescent bulbs. Seed setting occurred in 97.8% of plants per generation within 68.4 d. This approach was 30–45 d per generation faster than conventional single seed descent (SSD) methods. Therefore, RGT could increase plant generations per year using much less growth space compared to SSD, and in this way rapidly address new pulse breeding objectives using a fast (5.3 generations per year), reliable (97.9% survival rate), easy, and inexpensive (in vivo instead of in vitro) protocol.

Whole-genome duplication (polyploidy) occurs frequently and repeatedly within species of plants. According to the source of the genomes giving origin to a polyploid plant species, these are...

Grain amaranths (Amaranthusspp.) have been cultivated for thousands of years in Central and South America. Their grains are of high nutritional value, but the low yield needs to be increased by selection of superior genotypes from genetically diverse breeding populations. Amaranths are adapted to harsh conditions and can be cultivated on marginal lands although little is known about their physiology. The development of controlled growing conditions and efficient crossing methods is important for research on and improvement of this ancient crop. Grain amaranth was domesticated in the Americas and is highly self-fertilizing with a large inflorescence consisting of thousands of very small flowers. We evaluated three different crossing methods (open pollination, hot water emasculation and hand emasculation) for their efficiency in amaranth and validated them with genetic markers. We identified cultivation conditions that allow an easy control of flowering time by day length manipulation and achieved flowering times of 4 weeks and generation times of 2 months. All three different crossing methods successfully produced hybrid F1offspring, but with different success rates. Open pollination had the lowest (10%) and hand emasculation the highest success rate (74%). Hot water emasculation showed an intermediate success rate (26%) with a maximum of 94% success. It is simple to perform and suitable for a more large-scale production of hybrids. We further evaluated 11 single nucleotide polymorphism (SNP) markers and found that they were sufficient to validate all crosses of the genotypes used in this study for intra- and interspecific hybridizations. Despite its very small flowers, crosses in amaranth can be carried out efficiently and evaluated with inexpensive SNP markers. Suitable growth conditions strongly reduce the generation time and allow the control of plant height, flowering time, and seed production. In combination, this enables the rapid production of segregating populations which makes amaranth an attractive model for basic plant research but also facilitates further the improvement of this ancient crop by plant breeding.

正 大豆是短日照作物,在其第一片复叶至第三片复叶期间,增加遮光时间缩短光照,同时,给予适宜的温度条件,会显著提前开花结实.利用大豆的这个生理特性我们采取嫩粒播种,缩短光照,塑料薄膜覆盖,炉火加温,人工控制变温等各种措施,从1979年3月19日到1980年3月20日一年种植了四代;1980年3月15日到1981年3月20日又重复了此项试验,都获得了成功并取得有关的各种数据资料. 这项试验研究结果表明,在育种上改变选择方法,压缩分离世代的群体,从F_2代中多入选单株,采取一粒传的方法进行就地加代,在3—4年内可完成一个新品种的选育过程,比采用常规育种的方法,

A new plant breeding method—the biotron breeding system (BBS)—can rapidly produce advanced generations in rice (Oryza sativaL.) breeding. This method uses a growth chamber (biotron) with CO2control, accompanied by tiller removal and embryo rescue to decrease the period before seed maturity. However, tiller removal and embryo rescue are laborious and impractical for large populations. We investigated the influences of increased CO2, tiller removal, and root restriction on the days to heading (DTH) from seeding in growth chambers. The higher CO2concentration significantly decreased DTH, but tiller removal and root restriction had little effect on DTH and drastically reduced seed yield. Based on these findings, we propose a simplified BBS (the sBBS) that eliminates the need for tiller removal and embryo rescue, but controls CO2levels and day-length and maintains an appropriate root volume. Using the sBBS, we could reduce the interval between generations in ‘Nipponbare’ to less than 3 months, without onerous manipulations. To demonstrate the feasibility of the sBBS, we used it to develop isogenic lines using ‘Oborozuki’ as the donor parent for the low-amylose alleleWx1-1and ‘Akidawara’ as the recipient. We were able to perform four crossing cycles in a year.

Abstract A fast generation cycling system (FGCS) was developed in oat and triticale, allowing the production of pure line populations of the crops within 1-year timeframe. Twelve oat and 12 triticale cultivars were tested using the FGCS, and most of them completed a generation cycle within 48–6102days under the system achieving up to seven generations a year. This system involves growing plants under stressed conditions to promote reproduction and in02vitro culture of immature embryos bypassing full seed maturation. The developed system could be widely adopted in breeding and genetic studies of crops for producing desired segregating pure line populations, which could significantly shorten the breeding cycles.

The soybean [Glycine max (L.) Merrill] reproductive cycle represents more than 50% of the length of the total growth cycle. Immature embryo culture could be used to shorten this cycle. This study was conducted to develop an efficient technique to shorten the soybean reproductive cycle and to make it possible to develop recombinant lines from populations more rapidly. The importance of a pod pretreatment before embryo extraction, the effects of embryo age on germination rate, embryo position in the pod, and the composition of the germination medium (supplemented with sucrose or not) were analyzed to define an optimal technique. Plant recovery rate and genotype effects on germination were evaluated with 22 genotypes representing a broad genetic background. It was necessary to pretreat immature seed by exposing pods to 26 C for 4 d to induce germination. Best results (up to 100% germination) were obtained from embryos sampled at the end of lag phase of seed development (approximately 18 d after flowering). For three-seeded pods, the central embryos generally had a higher germination rate than distal and proximal embryos (25 and 44 percentage points, respectively). Whatever the embryo position in the pod, adding sucrose significantly increased the germination of embryos sampled 14 to 18 d after flowering. Plantlets were obtained from 73% of the germinated embryos and the length of cycle was reduced from 130 to 140 d to 65 to 70 d. Average germination of the 22 genotypes was 80%; thus, this technique, paired with the single seed descent method, provides soybean breeders with a tool to develop lines quickly.

With 2 figures and 4 tables Abstract We have developed an integrated breeding technology for cotton that can accelerate generation advancement to three or four times per year. This approach includes in vitro culturing of immature embryos into plantlets, which saves time because of no waiting for seed maturation. In addition to selection for kanamycin resistance and PCR identification of the gene of interest (here, insect resistance), we also incorporate methods such as plantlet grafting and growth regulation. In this way, embryos aged 20–30&nbsp;days postanthesis can develop directly into plantlets in another 10–15&nbsp;days. Here, kanamycin and PCR selection plantlets were grafted using a new and efficient technique called cotton joint graft, which can provide a reliable survival rate of 90–100%. Growth of the grafted plants was regulated for rapid development by adjusting the soil nutrients. We also treated the pedicels of hybridized or back-crossed bolls with a mixture of naphthalene acetic acid and gibberellic acid to prevent shedding. Over the course of 1&nbsp;year, we were able to produce three or four generations at intervals of about 90–120&nbsp;days, i.e. from immature embryo culture through pollination and fecundation. Using this procedure, we transferred the Cry1Ac gene into three recurrent cultivars, ‘Han93-2’, ‘Jimian20’ and ‘Nongda94-7’. This was accomplished through four backcross generations and one cycle of selfing. BC4F2 progenies were obtained within 1.5&nbsp;years, with each generation being completed between 89.0 and 117.3&nbsp;days.

Abstract Sorghum [Sorghum bicolor (L.) Moench] is a model C4 cereal for both basic and applied research. It has most of the traits of a model plant species: large embryos that are easy to rescue, moderate genome size of about 760 Mb, several unique traits not found in other species, plenty of seeds, and many important agronomic as well as commercial uses. However, it takes a long time to complete its breeding cycle. Other problems encountered during the research on sorghum breeding were early desiccation of embryos from mutants and wide hybridization, and the high-yielding cultivars and plants grown in controlled environments are usually uniculm, which limits their use in crossing to obtain both selfed and crossed seeds. The objective of this research was to find ways to obtain cross-and self-pollinated seeds from the same plant, conserve the vital embryos, and most important, shorten the breeding cycle. Two methods are reported here. The first method was to produce crossed as well as selfed seeds on the same panicle of the usually uni-culm plant. The second method was to carry out embryo rescue to save vital embryos as well as shorten the breeding cycle from the regular 17 to 11 wk. By these two methods, the breeding cycle of sorghum was made comparable or even shorter than that of other model crops, which would allow the development of breeding materials much faster.

Abstract Plant breeding is focused on continuously increasing crop production to meet the needs of an ever-growing world population, improving food quality to ensure a long and healthy life and address the problems of global warming and environment pollution, together with the challenges of developing novel sources of biofuels. The breeders' search for novel genetic combinations, with which to select plants with improved traits to satisfy both farmers and consumers, is endless. About half of the dramatic increase in crop yield obtained in the second half of the last century has been achieved thanks to the results of genetic improvement, while the residual advance has been due to the enhanced management techniques (pest and disease control, fertilization, and irrigation). Biotechnologies provide powerful tools for plant breeding, and among these ones, tissue culture, particularly haploid and doubled haploid technology, can effectively help to select superior plants. In fact, haploids (Hs), which are plants with gametophytic chromosome number, and doubled haploids (DHs), which are haploids that have undergone chromosome duplication, represent a particularly attractive biotechnological method to accelerate plant breeding. Currently, haploid technology, making possible through gametic embryogenesis the single-step development of complete homozygous lines from heterozygous parents, has already had a huge impact on agricultural systems of many agronomically important crops, representing an integral part in their improvement programmes. The aim of this review was to provide some background, recent advances, and future prospective on the employment of haploid technology through gametic embryogenesis as a powerful tool to support plant breeding.

Production of pure lines is an important step in biological studies and breeding of many crop plants. The major types of pure lines for biological studies and breeding include doubled haploid (DH) lines, recombinant inbred lines (RILs), and near isogenic lines (NILs). DH lines can be produced through microspore and megaspore culture followed by chromosome doubling while RILs and NILs can be produced through introgressions or repeated selfing of hybrids. DH approach was developed as a quicker method than conventional method to produce pure lines. However, its drawbacks of genotype-dependency and only a single chance of recombination limited its wider application. A recently developed fast generation cycling system (FGCS) achieved similar times to those of DH for the production of selfed pure lines but is more versatile as it is much less genotype-dependent than DH technology and does not restrict recombination to a single event. The advantages and disadvantages of the technologies and their produced pure line populations for different purposes of biological research and breeding are discussed. The development of a concept of completein vitromeiosis and mitosis system is also proposed. This could integrate with the recently developed technologies of single cell genomic sequencing and genome wide selection, leading to a complete laboratory based pre-breeding scheme.

The discovery of haploids in higher plants led to the use of doubled haploid (DH) technology in plant breeding. This article provides the state of the art on DH technology including the induction and identification of haploids, what factors influence haploid induction, molecular basis of microspore embryogenesis, the genetics underpinnings of haploid induction and its use in plant breeding, particularly to fix traits and unlock genetic variation. Both in vitro and in vivo methods have been used to induce haploids that are thereafter chromosome doubled to produce DH. Various heritable factors contribute to the successful induction of haploids, whose genetics is that of a quantitative trait. Genomic regions associated with in vitro and in vivo DH production were noted in various crops with the aid of DNA markers. It seems that F2 plants are the most suitable for the induction of DH lines than F1 plants. Identifying putative haploids is a key issue in haploid breeding. DH technology in Brassicas and cereals, such as barley, maize, rice, rye and wheat, has been improved and used routinely in cultivar development, while in other food staples such as pulses and root crops the technology has not reached to the stage leading to its application in plant breeding. The centromere-mediated haploid induction system has been used in Arabidopsis, but not yet in crops. Most food staples are derived from genomic resources-rich crops, including those with sequenced reference genomes. The integration of genomic resources with DH technology provides new opportunities for the improving selection methods, maximizing selection gains and accelerate cultivar development. Marker-aided breeding and DH technology have been used to improve host plant resistance in barley, rice, and wheat. Multinational seed companies are using DH technology in large-scale production of inbred lines for further development of hybrid cultivars, particularly in maize. The public sector provides support to national programs or small-medium private seed for the exploitation of DH technology in plant breeding.

Effective implementation of technology that facilitates accurate and high-throughput screening of thousands of field-grown lines is critical for accelerating crop improvement and breeding strategies for higher yield and disease tolerance. Progress in the development of field-based high throughput phenotyping methods has advanced considerably in the last 10 years through technological progress in sensor development and high-performance computing. Here, we review recent advances in high throughput field phenotyping technologies designed to inform the genetics of quantitative traits, including crop yield and disease tolerance. Successful application of phenotyping platforms to advance crop breeding and identify and monitor disease requires: (1) high resolution of imaging and environmental sensors; (2) quality data products that facilitate computer vision, machine learning and GIS; (3) capacity infrastructure for data management and analysis; and (4) automated environmental data collection. Accelerated breeding for agriculturally relevant crop traits is key to the development of improved varieties and is critically dependent on high-resolution, high-throughput field-scale phenotyping technologies that can efficiently discriminate better performing lines within a larger population and across multiple environments.

Abstract To ensure food security in the face of population growth, decreasing water and land for agriculture, and increasing climate variability, crop yields must increase faster than the current rates. Increased yields will require implementing novel approaches in genetic discovery and breeding. Here we demonstrate the potential of field-based high throughput phenotyping (HTP) on a large recombinant population of rice to identify genetic variation underlying important traits. We find that detecting quantitative trait loci (QTL) with HTP phenotyping is as accurate and effective as traditional labor-intensive measures of flowering time, height, biomass, grain yield, and harvest index. Genetic mapping in this population, derived from a cross of an modern cultivar (IR64) with a landrace (Aswina), identified four alleles with negative effect on grain yield that are fixed in IR64, demonstrating the potential for HTP of large populations as a strategy for the second green revolution.

正 关于自花授粉作物育种各种选择方法的特点曾进行过讨论。系谱法便于强选择和近交,而集团法则相反,有利于自然选择,在分离世代可能出现更多的基因重组。由此可见,如果

Abstract Genomic selection (GS) facilitates the rapid selection of superior genotypes and accelerates the breeding cycle. In this review, we discuss the history, principles, and basis of GS and genomic-enabled prediction (GP) as well as the genetics and statistical complexities of GP models, including genomic genotype0103environment (G0103E) interactions. We also examine the accuracy of GP models and methods for two cereal crops and two legume crops based on random cross-validation. GS applied to maize breeding has shown tangible genetic gains. Based on GP results, we speculate how GS in germplasm enhancement (i.e., prebreeding) programs could accelerate the flow of genes from gene bank accessions to elite lines. Recent advances in hyperspectral image technology could be combined with GS and pedigree-assisted breeding. Copyright 0008 2017 Elsevier Ltd. All rights reserved.

Pre-harvest sprouting (PHS) in wheat ( Triticum aestivum L.) is a significant problem. Introgression of genes controlling grain dormancy into white-grained bread wheat is one means of improving resistance to PHS. In this study seven dormant (containing the SW95-50213 and AUS1408 sources) non-dormant crosses were produced to investigate the effectiveness of selection for grain dormancy in early segregating generations. Each generation (F 1 4 ) was grown in a temperature controlled glasshouse with an extended photoperiod (i.e. continuous light). F 2 and F 3 generations were subject to selection. Five hundred harvest-ripe grains were tested for germination over a 14 day period, and the 100 most dormant grains were retained and grown-on to produce the next generation within each cross. The response to selection was assessed through analysis of the time to 50% germination (G 50 ) in the F 2 , F 3 and F 4 generations. In addition, changes in marker class frequencies for two SSR markers (barc170 and gpw2279) flanking a known quantitative trait locus (QTL) for grain dormancy on chromosome 4A were assessed in DNA from F 2 plants selected from early germinating (non-dormant) and late germinating (dormant) phenotypic extremes within each cross. Selection for grain dormancy in the F 2 and F 3 generations effectively recovered the dormant phenotype in all seven crosses, i.e. the F 4 generation was not significantly different from the dormant parent. Further, selection based on individual F 2 grains changed marker class frequencies for the 4A dormancy QTL; in most cases eliminating the marker class homozygous for the non-dormant alleles. Application of this screening method will enable breeders to better select for grain dormancy and may lead to development of new cultivars offering effective resistance to PHS in the near future.

Temperatures have increased and in-crop rainfall decreased over recent decades in many parts of the Australian wheat cropping region. With these trends set to continue or intensify, improving crop adaptation in the face of climate change is particularly urgent in this, already drought-prone, cropping region. Importantly, improved performance under water-limitation must be achieved while retaining yield potential during more favourable seasons. A multi-trait-based approach to improve wheat yield and yield stability in the face of water-limitation and heat has been instigated in northern Australia using novel phenotyping techniques and a nested association mapping (NAM) approach. An innovative laboratory technique allows rapid root trait screening of hundreds of lines. Using soil grown seedlings, the method offers significant advantages over many other lab-based techniques. Another recently developed method allows novel stay-green traits to be quantified objectively for hundreds of genotypes in standard field trial plots. Field trials in multiple locations and seasons allow evaluation of targeted trait values and identification of superior germplasm. Traits, including yield and yield components are measured for hundreds of NAM lines in rain fed environments under various levels of water-limitation. To rapidly generate lines of interest, the University of Queensland peed breeding method is being employed, allowing up to 7 plant generations per annum. A NAM population of over 1000 wheat recombinant inbred lines has been progressed to the F5 generation within 18 months. Genotyping the NAM lines with the genome-wide DArTseq molecular marker system provides up to 40,000 markers. They are now being used for association mapping to validate QTL previously identified in bi-parental populations and to identify novel QTL for stay-green and root traits. We believe that combining the latest techniques in physiology, phenotyping, genetics and breeding will increase genetic progress toward improved adaptation to water-limited environments.

With marker and phenotype information from observed populations, genomic selection(GS) can be used to establish associations between markers and phenotypes. It aims to use genome-wide markers to estimate the effects of all loci and thereby predict the genetic values of untested populations, so as to achieve more comprehensive and reliable selection and to accelerate genetic progress in crop breeding. GS models usually face the problem that the number of markers is much higher than the number of phenotypic observations.To overcome this issue and improve prediction accuracy, many models and algorithms,including GBLUP, Bayes, and machine learning have been employed for GS. As hot issues in GS research, the estimation of non-additive genetic effects and the combined analysis of multiple traits or multiple environments are also important for improving the accuracy of prediction. In recent years, crop breeding has taken advantage of the development of GS.The principles and characteristics of current popular GS methods and research progress in these methods for crop improvement are reviewed in this paper.

Background Advances in genotyping technology, such as genotyping by sequencing (GBS), are making genomic prediction more attractive to reduce breeding cycle times and costs associated with...

Abstract Genomic selection is an upgrading form of marker-assisted selection for quantitative traits, and it differs from the traditional marker-assisted selection in that markers in the entire genome are used to predict genetic values and the QTL detection step is skipped. Genomic selection holds the promise to be more efficient than the traditional marker-assisted selection for traits controlled by polygenes. Genomic selection for pure breed improvement is based on marker information and thus leads to cost-saving due to early selection before phenotypes are measured. When applied to hybrid breeding, genomic selection is anticipated to be even more efficient because genotypes of hybrids are predetermined by their inbred parents. Hybrid breeding has been an important tool to increase crop productivity. Here we proposed and applied an advanced method to predict hybrid performance, in which a subset of all potential hybrids is used as a training sample to predict trait values of all potential hybrids. The method is called genomic best linear unbiased prediction. The technology applied to hybrids is called genomic hybrid breeding. We used 278 randomly selected hybrids derived from 210 recombinant inbred lines of rice as a training sample and predicted all 21,945 potential hybrids. The average yield of top 100 selection shows a 16% increase compared with the average yield of all potential hybrids. The new strategy of marker-guided prediction of hybrid yields serves as a proof of concept for a new technology that may potentially revolutionize hybrid breeding.

Key message We have demonstrated that genomic selection in diverse wheat landraces for resistance to leaf, stem and strip rust is possible, as genomic breeding values were moderately accurate. Markers with large effects in the Bayesian analysis confirmed many known genes, while also discovering many previously uncharacterised genome regions associated with rust scores. Abstract Genomic selection, where selection decisions are based on genomic estimated breeding values (GEBVs) derived from genome-wide DNA markers, could accelerate genetic progress in plant breeding. In this study, we assessed the accuracy of GEBVs for rust resistance in 206 hexaploid wheat ( Triticum aestivum ) landraces from the Watkins collection of phenotypically diverse wheat genotypes from 32 countries. The landraces were genotyped for 5,568 SNPs using an Illumina iSelect 9K bead chip assay and phenotyped for field-based leaf rust (Lr), stem rust (Sr) and stripe rust (Yr) responses across multiple years. Genomic Best Linear Unbiased Prediction (GBLUP) and a Bayesian Regression method (BayesR) were used to predict GEBVs. Based on fivefold cross-validation, the accuracy of genomic prediction averaged across years was 0.35, 0.27 and 0.44 for Lr, Sr and Yr using GBLUP and 0.33, 0.38 and 0.30 for Lr, Sr and Yr using BayesR, respectively. Inclusion of PCR-predicted genotypes for known rust resistance genes increased accuracy more substantially when the marker was diagnostic ( Lr34/Sr57/Yr18) for the presence-absence of the gene rather than just linked ( Sr2 ). Investigation of the impact of genetic relatedness between validation and reference lines on accuracy of genomic prediction showed that accuracy will be higher when each validation line had at least one close relationship to the reference lines. Overall, the prediction accuracies achieved in this study are encouraging, and confirm the feasibility of genomic selection in wheat. In several instances, estimated marker effects were confirmed by published literature and results of mapping experiments using Watkins accessions.