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Leaf senescence is a destructive process that allows the efficient recycling of nutrients from dying leaves to growing parts of the plant. It is the final stage of leaf development that can be induced in response to stress. This makes leaf senescence an adaptive process that is highly beneficial for whole plant survival under unpredictable environmental conditions. Thus, the manipulation of this process has the potential to improve crop plants to become more climate resilient. In this review we compare leaf senescence processes between distantly related species to identify knowledge gaps and opportunities for plant improvement strategies. We describe that main signalling pathways controlled by carbohydrates, reactive oxygen species and hormones are conserved. However, the role of ethylene in age-induced leaf senescence in cereals is obscure. Moreover, downstream senescence regulatory signalling events are largely unknown, and these may be considerably different between members of annual dicots and cereals. Because leaf senescence regulation is so intricately connected to basic metabolic and developmental processes, we propose to increase research efforts to discover natural variation in senescence regulation and pinpoint gene variants that are tried and tested in nature. • Leaf senescence is an important nutrient recovery programme in a wide range of plant species. • Plant development and stress regulate leaf senescence. • Phytohormones and oxidative stress play similar roles in the induction of senescence in dicots and cereals. • Downstream signalling events often differ between dicots and cereals. • Harnessing natural variation in senescence regulatory genes can improve crop yield. [ABSTRACT FROM AUTHOR]

Key message: Leaf senescence in sorghum is primarily controlled by the progression, but not by the onset of senescence. The senescence-delaying haplotypes of 45 key genes accentuated from landraces to improved lines. Leaf senescence is a genetically programmed developmental process and plays a central role for plant survival and crop production by remobilising nutrients accumulated in senescent leaves. In theory, the ultimate outcome of leaf senescence is determined by the onset and progression of senescence, but how these two processes contribute to senescence is not fully illustrated in crops and the genetic basis for them is not well understood. Sorghum (Sorghum bicolor), which is known for the remarkable stay-green trait, is ideal for dissecting the genomic architecture underlying the regulation of senescence. In this study, a diverse panel of 333 sorghum lines was explored for the onset and progression of leaf senescence. Trait correlation analysis showed that the progression of leaf senescence, rather than the onset of leaf senescence, significantly correlated with variations of the final leaf greenness. This notion was further supported by GWAS, which identified 31 senescence-associated genomic regions containing 148 genes, of which 124 were related to the progression of leaf senescence. The senescence-delaying haplotypes of 45 key candidate genes were enriched in lines with extremely prolonged senescence duration, while senescence-promoting haplotypes in those with extremely accelerated senescence. Haplotype combinations of these genes could well explain the segregation of the senescence trait in a recombinant inbred population. We also demonstrated that senescence-delaying haplotypes of candidate genes were under strong selection during sorghum domestication and genetic improvement. Together, this research advanced our understanding of crop leaf senescence and provided a suite of candidate genes for functional genomics and molecular breeding. [ABSTRACT FROM AUTHOR]

Summary The onset of leaf senescence is controlled by leaf age and ethylene can promote leaf senescence within a specific age window. We exploited the interaction between leaf age and ethylene and isolated mutants with altered leaf senescence that are named as o nset of l eaf d eath (old ) mutants. Early leaf senescence mutants representing three genetic loci were selected and their senescence syndromes were characterised using phenotypical, physiological and molecular markers. old1 is represented by three recessive alleles and displayed earlier senescence both in air and upon ethylene exposure. The etiolated old1 seedlings exhibited a hypersensitive triple response. old2 is a dominant trait and the mutant plants were indistinguishable from the wild-type when grown in air but showed an earlier senescence syndrome upon ethylene treatment. old3 is a semi-dominant trait and its earlier onset of senescence is independent of ethylene treatment. Analyses of the chlorophyll degradation, ion leakage and SAG expression showed that leaf senescence was advanced in ethylene-treated old2 plants and in both air-grown and ethylene-treated old1 and old3 plants. Epistatic analysis indicated that OLD1 might act downstream of OLD2 and upstream of OLD3 and mediate the interaction between leaf age and ethylene. A genetic model was proposed that links the three OLD genes and ethylene into a regulatory pathway controlling the onset of leaf senescence. [ABSTRACT FROM AUTHOR]

Domestication and diversification have had profound effects on crop genomes. Originating in Africa and subsequently spreading to different continents, sorghum (Sorghum bicolor) has experienced multiple onsets of domestication and intensive breeding selection for various end uses. However, how these processes have shaped sorghum genomes is not fully understood. In the present study, population genomics analyses were performed on a worldwide collection of 445 sorghum accessions, covering wild sorghum and four end-use subpopulations with diverse agronomic traits. Frequent genetic exchanges were found among various subpopulations, and strong selective sweeps affected 14.68% (∼107.5 Mb) of the sorghum genome, including 3649, 4287, and 3888 genes during sorghum domestication, improvement of grain sorghum, and improvement of sweet sorghum, respectively. Eight different models of haplotype changes in domestication genes from wild sorghum to landraces and improved sorghum were observed, and Sh1 - and SbTB1 -type genes were representative of two prominent models, one of soft selection or multiple origins and one of hard selection or an early single domestication event. We also demonstrated that the Dry gene, which regulates stem juiciness, was unconsciously selected during the improvement of grain sorghum. Taken together, these findings provide new genomic insights into sorghum domestication and breeding selection, and will facilitate further dissection of the domestication and molecular breeding of sorghum. Population genomics analyses revealed the profound effects of domestication and genetic improvement on sorghum genomes. Eight different models of haplotype changes in domestication genes were observed, and Sh1 - and SbTB1 -type genes were representative of two prominent models of soft selection and hard selection, respectively. The genomic footprints identified here will facilitate further dissection of the domestication and molecular breeding of sorghum. [ABSTRACT FROM AUTHOR]

Summary: O‐acetylserine (thiol) lyases (OASTLs) are evolutionarily conserved proteins among many prokaryotes and eukaryotes that perform sulfur acquisition and synthesis of cysteine. A mutation in the cytosolic OASTL‐A1 protein ONSET OF LEAF DEATH3 (OLD3) was previously shown to reduce the OASTL activity of the old3‐1 protein in vitro and cause auto‐necrosis in specific Arabidopsis accessions. Here we investigated why a mutation in this protein causes auto‐necrosis in some but not other accessions. The auto‐necrosis was found to depend on Recognition of Peronospora Parasitica 1 (RPP1)‐like disease resistance R gene(s) from an evolutionarily divergent R gene cluster that is present in Ler‐0 but not the reference accession Col‐0. RPP1‐like gene(s) show a negative epistatic interaction with the old3‐1 mutation that is not linked to reduced cysteine biosynthesis. Metabolic profiling and transcriptional analysis further indicate that an effector triggered‐like immune response and metabolic disorder are associated with auto‐necrosis in old3‐1 mutants, probably activated by an RPP1‐like gene. However, the old3‐1 protein in itself results in largely neutral changes in primary plant metabolism, stress defence and immune responses. Finally, we showed that lack of a functional OASTL‐A1 results in enhanced disease susceptibility against infection with virulent and non‐virulent Pseudomonas syringae pv. tomato DC3000 strains. These results reveal an interaction between the cytosolic OASTL and components of plant immunity. [ABSTRACT FROM AUTHOR]

Key message: Twelve QTL for flowering and leaf number were detected. The ZmWRKY14Hap4 could increase leaf number, flowering time and biomass yield which are promising for silage maize breeding. Silage maize, one of the most important feedstock for ruminants, is widely grown from temperate regions to the tropics. Flowering time and leaf number are two significantly correlated traits and important for the quality, adaptation and biomass yield of silage maize. In this study, a recombinant inbred line population consisting of 215 individuals and an association panel of 369 inbred lines were analysed in field conditions in three locations for 2 consecutive years, and five, four and three quantitative trait loci for the total leaf number, days to anthesis (DTA) and silking (DTS) were detected, which could explain 48.55, 35.37 and 34.22% of total phenotypic variation, respectively. Association analysis of qLN10 on chromosome 10 found that ZmWRKY14 was the candidate gene for leaf number, whose expression level was negatively correlated with the leaf number. There are five haplotypes for ZmWRKY14, and haplotype 4 could significantly increase flowering time, leaf number and biomass yield, but has no obvious influence on ear weight. The optimal allelic combination of ZmWRKY14 and ZCN8 could further increase leaf number and biomass yield. The results will provide important genetic information for silage maize breeding. [ABSTRACT FROM AUTHOR]

Background: As the fifth major cereal crop originated from Africa, sorghum (Sorghum bicolor) has become a key C4 model organism for energy plant research. With the development of high-throughput detection technologies for various omics data, much multi-dimensional and multi-omics information has been accumulated for sorghum. Integrating this information may accelerate genetic research and improve molecular breeding for sorghum agronomic traits. Results: We updated the Sorghum Genome SNP Database (SorGSD) by adding new data, new features and renamed it to Sorghum Genome Science Database (SorGSD). In comparison with the original version SorGSD, which contains SNPs from 48 sorghum accessions mapped to the reference genome BTx623 (v2.1), the new version was expanded to 289 sorghum lines with both single nucleotide polymorphisms (SNPs) and small insertions/deletions (INDELs), which were aligned to the newly assembled and annotated sorghum genome BTx623 (v3.1). Moreover, phenotypic data and panicle pictures of critical accessions were provided in the new version. We implemented new tools including ID Conversion, Homologue Search and Genome Browser for analysis and updated the general information related to sorghum research, such as online sorghum resources and literature references. In addition, we deployed a new database infrastructure and redesigned a new user interface as one of the Genome Variation Map databases. The new version SorGSD is freely accessible online at http://ngdc.cncb.ac.cn/sorgsd/. Conclusions: SorGSD is a comprehensive integration with large-scale genomic variation, phenotypic information and incorporates online data analysis tools for data mining, genome navigation and analysis. We hope that SorGSD could provide a valuable resource for sorghum researchers to find variations they are interested in and generate customized high-throughput datasets for further analysis. [ABSTRACT FROM AUTHOR]

Key message: The importance and potential of the multi-purpose crop sorghum in global food security have not yet been fully exploited, and the integration of the state-of-art genomics and high-throughput technologies into breeding practice is required. Sorghum, a historically vital staple food source and currently the fifth most important major cereal, is emerging as a crop with diverse end-uses as food, feed, fuel and forage and a model for functional genetics and genomics of tropical grasses. Rapid development in high-throughput experimental and data processing technologies has significantly speeded up sorghum genomic researches in the past few years. The genomes of three sorghum lines are available, thousands of genetic stocks accessible and various genetic populations, including NAM, MAGIC, and mutagenised populations released. Functional and comparative genomics have elucidated key genetic loci and genes controlling agronomical and adaptive traits. However, the knowledge gained has far away from being translated into real breeding practices. We argue that the way forward is to take a genome-based approach for tailored designing of sorghum as a multi-functional crop combining excellent agricultural traits for various end uses. In this review, we update the new concepts and innovation systems in crop breeding and summarise recent advances in sorghum genomic researches, especially the genome-wide dissection of variations in genes and alleles for agronomically important traits. Future directions and opportunities for sorghum breeding are highlighted to stimulate discussion amongst sorghum academic and industrial communities. [ABSTRACT FROM AUTHOR]

Leaf senescence is important for crop yield as delaying it can increase the average yield. In this study, population genetics and transcriptomic profiling were combined to dissect its genetic basis in maize. To do this, the progenies of an elite maize hybrid Jidan27 and its parental lines Si-287 (early senescence) and Si-144 (stay-green), as well as 173 maize inbred lines were used. We identified two novel loci and their candidate genes, Stg3 (ZmATG18b) and Stg7 (ZmGH3.8), which are predicted to be members of autophagy and auxin pathways, respectively. Genomic variations in the promoter regions of these two genes were detected, and four allelic combinations existed in the examined maize inbred lines. The Stg3 Si-144/ Stg7 Si-144 allelic combination with lower ZmATG18b expression and higher ZmGH3.8 expression could distinctively delay leaf senescence, increase ear weight and the improved hybrid of NIL- Stg3Si-144 / Stg7Si-144 × Si-144 significantly reduced ear weight loss under drought stress, while opposite effects were observed in the Stg3 Si-287/ Stg7 Si-287 combination with a higher ZmATG18b expression and lower ZmGH3.8 expression. Thus, we identify a potential interaction between autophagy and auxin which could modulate the timing of maize leaf senescence. [ABSTRACT FROM AUTHOR]

Background: In sorghum (Sorghum bicolor), one paramount breeding objective is to increase grain quality. The nutritional quality and end use value of sorghum grains are primarily influenced by the proportions of tannins, starch and proteins, but the genetic basis of these grain quality traits remains largely unknown. This study aimed to dissect the natural variation of sorghum grain quality traits and identify the underpinning genetic loci by genome-wide association study. Results: Levels of starch, tannins and 17 amino acids were quantified in 196 diverse sorghum inbred lines, and 44 traits based on known metabolic pathways and biochemical interactions amongst the 17 amino acids calculated. A Genome-wide association study (GWAS) with 3,512,517 SNPs from re-sequencing data identified 14, 15 and 711 significant SNPs which represented 14, 14, 492 genetic loci associated with levels of tannins, starch and amino acids in sorghum grains, respectively. Amongst these significant SNPs, two SNPs were associated with tannin content on chromosome 4 and colocalized with three previously identified loci for Tannin1, and orthologs of Zm1 and TT16 genes. One SNP associated with starch content colocalized with sucrose phosphate synthase gene. Furthermore, homologues of opaque1 and opaque2 genes associated with amino acid content were identified. Using the KEGG pathway database, six and three candidate genes of tannins and starch were mapped into 12 and 3 metabolism pathways, respectively. Thirty-four candidate genes were mapped into 16 biosynthetic and catabolic pathways of amino acids. We finally reconstructed the biosynthetic pathways for aspartate and branched-chain amino acids based on 15 candidate genes identified in this study. Conclusion: Promising candidate genes associated with grain quality traits have been identified in the present study. Some of them colocalized with previously identified genetic regions, but novel candidate genes involved in various metabolic pathways which influence grain quality traits have been dissected. Our study acts as an entry point for further validation studies to elucidate the complex mechanisms controlling grain quality traits such as tannins, starch and amino acids in sorghum. [ABSTRACT FROM AUTHOR]

Sorghum (Sorghum bicolor) is the fifth most popular crop worldwide and a C4 model plant. Domesticated sorghum comes in many forms, including sweet cultivars with juicy stems and grain sorghum with dry, pithy stems at maturity. The Dry locus, which controls the pithy/juicy stem trait, was discovered over a century ago. Here, we found that Dry gene encodes a plant-specific NAC transcription factor. Dry was either deleted or acquired loss-of-function mutations in sweet sorghum, resulting in cell collapse and altered secondary cell wall composition in the stem. Twenty-three Dry ancestral haplotypes, all with dry, pithy stems, were found among wild sorghum and wild sorghum relatives. Two of the haplotypes were detected in domesticated landraces, with four additional dry haplotypes with juicy stems detected in improved lines. These results imply that selection for Dry gene mutations was a major step leading to the origin of sweet sorghum. The Dry gene is conserved in major cereals; fine-tuning its regulatory network could provide a molecular tool to control crop stem texture. [ABSTRACT FROM AUTHOR]

Compared to other potential feedstocks such as sugarcane, sugar beet, maize, and watermelon, sweet sorghum possesses higher levels of directly fermentable reducing sugars within the culm and the ability to accumulate high biomass under low-input production systems. In addition, it is tolerant to drought and has more efficient utilization of solar radiation and nitrogen-based fertilizers than maize and sugar cane on marginal lands that are not optimal for food production. These collectively make sweet sorghum to be considered with huge potential as a biofuel crop. Novel phenotypes generated during plant domestication and continued crop improvements via artificial selection constitute the domestication syndrome ( Am. J. Bot., 101, 2014, 1711). Here, we draw an analogy and introduce the term the biofuel syndrome to refer to a suite of sweet sorghum traits, such as plant architecture (root, leave, and stem), flowering time and maturity as well as biomass bioconversion efficiency, that are associated with biofuel production and distinguish it from grain and forage sorghum traits. We discuss the biofuel syndrome amenable for targeted genetic modulation and what is currently known about the genetics and genomics of these traits as a potential route to optimize sweet sorghum for biofuel production. Continuous availability of sweet sorghum, transport and storing much mass and minimizing the postharvest loss of fermentable sugars are fundamental to exploiting sweet sorghum as a bioenergy crop. Due to the relatively short history of sweet sorghum breeding, we consider the development of ideotypes adapting to various phenological requirements to maximize the rapid deployment of sweet sorghum for biofuel production. [ABSTRACT FROM AUTHOR]

Key message: Eight morphological, biomass and biofuel traits were found with high broad-sense heritability and 18 significant QTLs discovered including one locus controlling the stem juice trait for sorghum grown in Denmark and China. Sweet sorghum with tall plant, fast maturation and high stem Brix content can be bred as a biofuel crop for Northern Europe. Abstract: Sweet sorghum ( Sorghum bicolour), a native tropical C crop, has attracted interest as a bioenergy crop in northern countries due to its juice-rich stem and high biomass production. Little is known about the traits important for its adaptation to high altitude climatic conditions and their genetic controls. Recombinant inbred lines derived from a cross between a sweet and a grain kaoliang sorghum were used in five field trials in Denmark and in China to identify the stability and genetic controls of morphological, biomass and biofuel traits during three consecutive summers with short duration, cool temperatures and long days. Eight out of 15 traits were found with high broad-sense heritability. Strong positive correlations between plant height and biomass traits were observed, while Brix and juice content were under different genetic controls. Using newly developed PAV (presence and absence variant) markers, 53 QTLs were detected, of which 18 were common for both countries, including a locus controlling stem juice (LOD score = 20.5, r = 37.5 %). In Denmark, the heading stage correlated significantly with biomass and morphology traits, and two significant maturity QTLs detected on chromosomes SBI01 and SBI02 co-localised with QTLs previously associated with early-stage chilling tolerance, suggesting that accelerating maturation might be a means of coping with low-temperature stress. Our results suggest that selection for tall and fast maturating sorghum plants combined with high Brix content represents a high potential for breeding bioenergy crop for Northern Europe. [ABSTRACT FROM AUTHOR]

Key message: 5,511 genic small-size PAVs in sorghum were identified and examined, including the pattern and the function enrichment of PAV genes. 325 PAV markers were developed to construct a genetic map. Abstract: Presence/absence variants (PAVs) correlate closely to the phenotypic variation, by impacting plant genome sizes and the adaption to the environment. To shed more light on their genome-wide patterns, functions and the possibility of using them as molecular markers, we generated next generation genome sequencing data for four sorghum inbred lines and used associated bioinformatic pipelines to identify small-size PAVs (40-10 kb). Five thousand five hundreds and eleven genic PAVs (40-10 kb) were identified and found to affect 3,238 genes. These PAVs were mainly distributed on the sub-telomeric regions, but the highest proportions occurred in the vicinity of the centromeric regions. One of the prominent features of the PAVs is the high occurrence of long terminal repeats retrotransposons and DNA transposons. PAVs caused various alterations to gene structure, primarily including the coding sequence variants, intron variants, transcript ablation, and initiator codon changes. The genes affected by PAVs were significantly enriched in those involved in stress responses and protein modification. We used 325 PAVs polymorphic between two sorghum inbred lines Ji2731 and E-Tian, together with 49 SSR markers, and constructed a genetic map, which consisted of 10 linkage groups corresponding to the 10 chromosomes of sorghum and spanned 1,430.3 cM in length covering 97 % of the physical genome. The resources reported here should be useful for genetic study and breeding of sorghum and related species. [ABSTRACT FROM AUTHOR]

Stress tolerance is a prerequisite for the success of biofuel production, which normally requires the use of marginal lands and nonfood biofuel feedstocks. Sorghum is known for its ability to withstand stress conditions, however, terminal stresses threaten its growth and development negatively impacting yield and sugar accumulation. It is crucial, therefore, that research aimed at developing sorghum resistance to stress factors should be pursued to expand the range of its growth to marginal and barren soils to meet the needs of a growing population, changing diets, and biofuel production. In this context, the leaf architectural trait of stay-green drought tolerance, in addition to salinity, cold, and aluminium toxicity and biotic stress tolerance and their genetic basis discussed in this review are expected to be available in future sweet sorghum ideotypes. Also highlighted is the key role of efficient management of farming systems, in particular the use of herbicides to control weeds, to ensure the sustainability of the sweet sorghum biomass productions. [ABSTRACT FROM AUTHOR]

In halophytic plants, the high-affinity potassium transporter HKT gene family can selectively uptake K+ in the presence of toxic concentrations of Na+. This has so far not been well examined in glycophytic crops. Here, we report the characterization of SbHKT1;4, a member of the HKT gene family from Sorghum bicolor. Upon Na+ stress, SbHKT1;4 expression was more strongly upregulated in salt-tolerant sorghum accession, correlating with a better balanced Na+/K+ ratio and enhanced plant growth. Heterogeneous expression analyses in mutants of Saccharomyces cerevisiae and Arabidopsis thaliana indicated that overexpressing SbHKT1;4 resulted in hypersensitivity to Na+ stress, and such hypersensitivity could be alleviated with the supply of elevated levels of K+, implicating that SbHKT1;4 may mediate K+ uptake in the presence of excessive Na+. Further electrophysiological evidence demonstrated that SbHKT1;4 could transport Na+ and K+ when expressed in Xenopus laevis oocytes. The relevance of the finding that SbHKT1;4 functions to maintain optimal Na+/K+ balance under Na+ stress to the breeding of salt-tolerant glycophytic crops is discussed. [ABSTRACT FROM AUTHOR]

The presence/absence variants (PAVs) are a major source of genome structural variation and have profound effects on phenotypic and genomic variation in animals and humans. However, little is understood about PAVs in plant genomes. Our previous resequencing effort on three sorghum ( Sorghum bicolour L.) genomes, each 12× coverage, uncovered 5 364 PAVs. Here, we report a detailed characterization of 51 large-size (>30 kb) PAVs. These PAVs spanned a total size of 2.92 Mb of the sorghum genome containing 202 known and predicted genes, including 38 genes annotated to encode cell death and stress response genes. The PAVs varied considerably for repeat sequences and mobile elements with DNA transposons as the major components. The frequency and distribution of these PAVs differed substantially across 96 sorghum inbred lines, and the low- and high frequency PAVs differed in their gene categories. This report shed new light on the occurrence and diversity of PAVs in sorghum genomes. Our research exemplifies a new perspective to explore genome structural variation for genetic improvement in plant breeding. [ABSTRACT FROM AUTHOR]

Sodium carbonate (Na2CO3) presents a huge challenge to plants by the combined damaging effects of Na+, high pH, and CO32-. Little is known about the cellular responses to Na2CO3 stress. In this study, the transcriptome of maize ( Zea mays L. cv. B73) roots exposed to Na2CO3 stress for 5 h was compared with those of NaCl and NaOH stresses. The expression of 8,319 genes, representing over a quarter of the total number of genes in the maize genome, was altered by Na2CO3 stress, and the downregulated genes (5,232) outnumbered the upregulated genes (3,087). The effects of Na2CO3 differed from those of NaCl and NaOH, primarily by downregulating different categories of genes. Pathways commonly altered by Na2CO3, NaCl, and NaOH were enriched in phenylpropanoid biosynthesis, oxidation of unsaturated fatty acids, ATP-binding cassette (ABC) transporters, as well as the metabolism of secondary metabolites. Genes for brassinosteroid biosynthesis were specifically upregulated by Na2CO3, while genes involved in ascorbate and aldarate metabolism, protein processing in the endoplasmic reticulum and by N-glycosylation, fatty acid biosynthesis, and the circadian rhythm were downregulated. This work provides the first holistic picture of early transcriptomic adaptation to Na2CO3 stress, and highlights potential molecular pathways that could be manipulated to improve tolerance in maize. [ABSTRACT FROM AUTHOR]

Abstract: Xylans are the major hemicelluloses in grasses, but their effects on biomass saccharification remain unclear. In this study, we examined the 79 representative Miscanthus accessions that displayed a diverse cell wall composition and varied biomass digestibility. Correlation analysis showed that hemicelluloses level has a strong positive effect on lignocellulose enzymatic digestion after NaOH or H2SO4 pretreatment. Characterization of the monosaccharide compositions in the KOH-extractable and non-KOH-extractable hemicelluloses indicated that arabinose substitution degree of xylan is the key factor that positively affects biomass saccharification. The xylose/arabinose ratio after individual enzyme digestion revealed that the arabinose in xylan is partially associated with cellulose in the amorphous regions, which negatively affects cellulose crystallinity for high biomass digestibility. The results provide insights into the mechanism of lignocellulose enzymatic digestion upon pretreatment, and also suggest a goal for the genetic modification of hemicelluloses towards the bioenergy crop breeding of Miscanthus and grasses. [Copyright &y& Elsevier]

Leaf senescence can impact crop production by either changing photosynthesis duration, or by modifying the nutrient remobilization efficiency and harvest index. The doubling of the grain yield in major cereals in the last 50 years was primarily achieved through the extension of photosynthesis duration and the increase in crop biomass partitioning, two things that are intrinsically coupled with leaf senescence. In this review, we consider the functionality of a leaf as a function of leaf age, and divide a leaf's life into three phases: the functionality increasing phase at the early growth stage, the full functionality phase, and the senescence and functionality decreasing phase. A genetic framework is proposed to describe gene actions at various checkpoints to regulate leaf development and senescence. Four categories of genes contribute to crop production: those which regulate (I) the speed and transition of early leaf growth, (II) photosynthesis rate, (III) the onset and (IV) the progression of leaf senescence. Current advances in isolating and characterizing senescence regulatory genes are discussed in the leaf aging and crop production context. We argue that the breeding of crops with leaf senescence ideotypes should be an essential part of further crop genetic improvement. [ABSTRACT FROM AUTHOR]

High‐resolution melting (HRM) analysis relies on the use of fluorescent dyes, such as LCGreen, ResoLight, and SYTO9, which bind in a saturated manner to the double‐stranded DNAs. These dyes are expensive in use and may not be affordable when dealing with a large quantity of samples. EvaGreen is a much cheaper DNA helix intercalating dye and has been used in quantitative real‐time polymerase chain reaction (PCR) and post‐PCR DNA melt curve analysis. Here we report on the development of an EvaGreen‐based HRM analysis and its performance, in comparison with the popular LCGreen‐based HRM analysis, in detection of DNA polymorphism in plants. We found that various polymorphisms ranged from single nucleotide polymorphisms (SNPs) to Indels were equally detected by using EvaGreen‐ or LCGreen‐based HRM. EvaGreen dye was sensitive enough in discovery of SNPs in fivefold pooled samples. Using this economical dye we successfully identified multiple novel mutant alleles of Gln1‐3 gene, which produces a cytosolic glutamine synthetase isoenzyme (GS1), in a maize ethyl methanesulfonate (EMS)‐mutagenized library, and genotyped rice mapping populations with SNP markers. The current results suggest that EvaGreen is a promising dye for HRM analysis for its ease to use and cost effectiveness. [ABSTRACT FROM AUTHOR]

With increasing environmental pressure and soil pollution, sustainable energy and food production for a steadily growing world population is a grand challenge. Globally, nearly 12 million hectares of croplands are contaminated by cadmium (Cd), and how to develop a production system for the cleaning and utilisation of such contaminated land is essential for sustainability. Herein, a diverse panel of 166 sorghum accessions was grown in typical Cd-contaminated fields in two consecutive years, and the effect of different accessions and organs on the phytoremediation potential was evaluated by analysing the Cd concentrations of stems, leaves and grains at maturity. Both the bioaccumulation factors (BCFs) and the aboveground Cd accumulation varied substantially and the differences were up to 13–24 fold. The aboveground Cd accumulation was positively associated with important bioenergy traits including biomass, stem Brix, internode numbers and plant height, as envisaged by the high Cd concentration in sweet sorghum accessions, while BCF was significantly negatively correlated with relevant agronomic traits except Brix. The genetic regulation of Cd concentration in grains is different from those in leaves and stems, which allowed us to screen for three types of sorghum resources with the potential to couple soil phytoremediation with the production of bioethanol, safe grains and forage. A sorghum farming system was further proposed, which could reduce soil Cd concentration below the safe level within 12 years and obtain economic returns of about 70.5–169.5 million Chinese Yuan (CNY) by producing bioethanol, safe grains and forage in one season in 30% of the Cd-contaminated soil in China. A sorghum farming system for phytoremediation of cadmium-contaminated soil and safe crop production. Image 1 • Large variation was found in Cd concentration and accumulation amongst diverse sorghum accessions. • Three types of sorghums were selected to couple phytoremediation with the production of bioethanol, safe grain and forage. • A sorghum farming system is proposed for remediation of Cd-polluted soil within 12 years with considerable economic benefit. [ABSTRACT FROM AUTHOR]