Showing papers in "Crop Journal in 2021"
TL;DR: It is suggested that ABA and JA are required for priming-induced drought tolerance in wheat, with JA acting upstream of ABA, as indicated by a finding of no significant difference from PD under drought stress.
Abstract: Drought stress is a limiting factor for wheat production and food security. Drought priming has been shown to increase drought tolerance in wheat. However, the underlying mechanisms are unknown. In the present study, the genes encoding the biosynthesis and metabolism of abscisic acid (ABA) and jasmonic acid (JA), as well as genes involved in the ABA and JA signaling pathways were up-regulated by drought priming. Endogenous concentrations of JA and ABA increased following drought priming. The interplay between JA and ABA in plant responses to drought priming was further investigated using inhibitors of ABA and JA biosynthesis. Application of fluridone (FLU) or nordihydroguaiaretic acid (NDGA) to primed plants resulted in lower chlorophyll-fluorescence parameters and activities of superoxide dismutase and glutathione reductase, and higher cell membrane damage, compared to primed plants (PD) under drought stress. NDGA + ABA, but not FLU + JA, restored priming-induced tolerance, as indicated by a finding of no significant difference from PD under drought stress. Under drought priming, NDGA induced the suppression of ABA accumulation, while FLU did not affect JA accumulation. These results were consistent with the expression of genes involved in the biosynthesis of ABA and JA. They suggest that ABA and JA are required for priming-induced drought tolerance in wheat, with JA acting upstream of ABA.
80 citations
TL;DR: In this paper, the major molecular mechanisms underlying salinity tolerance in rice and further discuss the limitations in breeding for salinity tolerant rice (Oryza sativa L.) are discussed.
Abstract: Salinity is one of the major abiotic stresses which impose constraints to plant growth and production. Rice (Oryza sativa L.) is one of the most important staple food crops and a model monocot plant. Its production is expanding into regions that are affected by soil salinity, requiring cultivars more tolerant to saline conditions. Understanding the molecular mechanisms of such tolerance could lay a foundation for varietal improvement of salt tolerance in rice. In spite of extensive studies exploring the mechanism of salt tolerance, there has been limited progress in breeding for increased salinity tolerance. In this review, we summarize the information about the major molecular mechanisms underlying salinity tolerance in rice and further discuss the limitations in breeding for salinity tolerance. We show that numerous gene families and interaction networks are involved in the regulation of rice responses to salinity, prompting a need for a comprehensive functional analysis. We also show that most studies are based on whole-plant level analyses with only a few reports focused on tissue- and/or cell-specific gene expression. More details of salt-responsive channel and transporter activities at tissue- and cell-specific level still need to be documented before these traits can be incorporated into elite rice germplasm. Thus, future studies should focus on diversity of available genetic resources and, particular, wild rice relatives, to re-incorporate salinity tolerance traits lost during domestication.
71 citations
TL;DR: The antagonistic effect of K on Mg is stronger than that of Mg on K in root absorption and transport within plants, indicating that the balanced use of K and Mg fertilizers is necessary for sustaining high plant-available Mg and alleviating K-induced Mg deficiency, especially in plant species with high K demand or in high-available-K soil.
Abstract: Magnesium (Mg) affects various critical physiological and biochemical processes in higher plants, and its deficiency impedes plant growth and development. Although potassium (K)-induced Mg deficiency in agricultural production is widespread, the specific relationship of K with Mg and especially its competitive nature is poorly understood. This review summarizes current knowledge on the interactions between K and Mg with respect to their root uptake, root-to-shoot translocation and distribution in plants. Their synergistic effects on certain physiological functions are also described. The antagonistic effect of K on Mg is stronger than that of Mg on K in root absorption and transport within plants, indicating that the balanced use of K and Mg fertilizers is necessary for sustaining high plant-available Mg and alleviating K-induced Mg deficiency, especially in plant species with high K demand or in high-available-K soil. The relationship between Mg and K in plant tissues may be antagonistic or synergistic depending on plant species, cell type, leaf age, source- and sink organs. There are synergistic effects of K and Mg on photosynthesis, carbohydrate transport and allocation, nitrogen metabolism, and turgor regulation. Definition of optimal K/Mg ratios for soils and plant tissues is desirable for maintaining proper nutritional status in plants, leading to a physiological state supporting crop production. Future research should concentrate on identifying the physiological and molecular mechanisms underlying the interactions between K and Mg in a given physiological function.
66 citations
TL;DR: Recent research progress on four aspects of plant physiological response to salt stress are discussed, with particular attention to hormonal and gene expression regulation and salt tolerance signaling pathways in rice.
Abstract: Crop yield loss due to soil salinization is an increasing threat to agriculture worldwide. Salt stress drastically affects the growth, development, and grain productivity of rice (Oryza sativa L.), and the improvement of rice tolerance to salt stress is a desirable approach for meeting increasing food demand. The main contributors to salt toxicity at a global scale are Na+ and Cl− ions, which affect up to 50% of irrigated soils. Plant responses to salt stress occur at the organismic, cellular, and molecular levels and are pleiotropic, involving (1) maintenance of ionic homeostasis, (2) osmotic adjustment, (3) ROS scavenging, and (4) nutritional balance. In this review, we discuss recent research progress on these four aspects of plant physiological response, with particular attention to hormonal and gene expression regulation and salt tolerance signaling pathways in rice. The information summarized here will be useful for accelerating the breeding of salt-tolerant rice.
64 citations
TL;DR: An overview of crop phenomics research from technological and platform viewpoints at various scales, including microscopic, ground-based, and aerial phenotyping and phenotypic data analysis is offered.
Abstract: With the rapid development of genetic analysis techniques and crop population size, phenotyping has become the bottleneck restricting crop breeding. Breaking through this bottleneck will require phenomics, defined as the accurate, high-throughput acquisition and analysis of multi-dimensional phenotypes during crop growth at organism-wide levels, ranging from cells to organs, individual plants, plots, and fields. Here we offer an overview of crop phenomics research from technological and platform viewpoints at various scales, including microscopic, ground-based, and aerial phenotyping and phenotypic data analysis. We describe recent applications of high-throughput phenotyping platforms for abiotic/biotic stress and yield assessment. Finally, we discuss current challenges and offer perspectives on future phenomics research.
54 citations
TL;DR: This review summarizes HS-caused symptoms in rice and progress in heat-stress sensing and signal cascade research, and proposes approaches for improving rice thermotolerance in future.
Abstract: Heat stress (HS) caused by rapidly warming climate has become a serious threat to global food security. Rice (Oryza sativa L.) is a staple food crop for over half of the world’s population, and its yield and quality are often reduced by HS. There is an urgent need for breeding heat-tolerant rice cultivars. Rice plants show various morphological and physiological symptoms under HS. Precise analysis of the symptoms (phenotyping) is essential for the selection of elite germplasm and the identification of thermotolerance genes. In response to HS, rice plants trigger a cascade of events and activate complex transcriptional regulatory networks. Protein homeostasis under HS is especially important for rice thermotolerance, which is affected by protein quality control, effective elimination of toxic proteins, and translational regulation. Although some agronomic and genetic approaches for improving heat tolerance have been adopted in rice, the molecular mechanisms underlying rice response to HS are still elusive, and success in engineering rice thermotolerance in breeding has been limited. In this review, we summarize HS-caused symptoms in rice and progress in heat-stress sensing and signal cascade research, and propose approaches for improving rice thermotolerance in future.
52 citations
TL;DR: This review summarizes current knowledge of Cd accumulation and detoxification in plants and initiates a series of mechanisms to reduce Cd toxicity, including cell wall adsorption, cytoplasmic chelation, and vacuolar sequestration.
Abstract: As a consequence of industrial development, soil Cd pollution leads to crop contamination by Cd, posing a threat to food safety and human health Excessive accumulation of Cd in plants also inhibits their growth via oxidative stress damage to their photosynthetic systems Through evolutionary selection, plants have developed a set of efficient strategies to respond to Cd in their environments These include the accumulation and detoxification of heavy metals Cd is absorbed by plant roots through the apoplastic and symplastic pathways and then translocated to plant shoots via xylem loading, long-distance transport, and phloem redistribution Simultaneously, plants initiate a series of mechanisms to reduce Cd toxicity, including cell wall adsorption, cytoplasmic chelation, and vacuolar sequestration This review summarizes current knowledge of Cd accumulation and detoxification in plants
49 citations
TL;DR: How the growth and development of cotton is impaired by waterlogging is reviewed, focusing on the three strategies associated with tolerance and adaptation to the stress, and agronomic measures and prospects for mitigating the adverse effects of waterlogged stress.
Abstract: Over the last few decades, waterlogging stress has increasingly threatened global cotton production. Waterlogging results in reduced soil oxygen, impairing the growth and development of this valuable crop and often resulting in severe yield loss or crop failure. However, as cotton has an indeterminate growth habit, it is able to adapt to waterlogging stress by activating three mechanisms: the escape, quiescence, and self-regulating compensation mechanisms. The escape mechanism includes accelerated growth, formation of adventitious roots, and production of aerenchyma. The quiescence mechanism involves reduced biomass accumulation and energy dissipation via physiological, biochemical, and molecular events. The self-regulation compensation mechanism allows plants to exploit their indeterminate growth habit and compensatory growth ability by accelerating growth and development following relief from waterlogging stress. We review how the growth and development of cotton is impaired by waterlogging, focusing on the three strategies associated with tolerance and adaptation to the stress. We discuss agronomic measures and prospects for mitigating the adverse effects of waterlogging stress.
47 citations
TL;DR: A new strategy for identifying robust and reliable meta-QTL (mQTL) that can be used for improvement of wheat FHB resistance is described, which may lead to a comprehensive molecular breeding platform for improving wheat resistance to FHB.
Abstract: Fusarium head blight (FHB) is a global wheat disease that devastates wheat production. Resistance to FHB spread within a wheat spike (type II resistance) and to mycotoxin accumulation in infected kernel (type III resistance) are the two main types of resistance. Of hundreds of QTL that have been reported, only a few can be used in wheat breeding because most show minor and/or inconsistent effects in different genetic backgrounds. We describe a new strategy for identifying robust and reliable meta-QTL (mQTL) that can be used for improvement of wheat FHB resistance. It involves integration of mQTL analysis with mQTL physical mapping and identification of single-copy markers and candidate genes. Using meta-analysis, we consolidated 625 original QTL from 113 publications into 118 genetic map-based mQTL (gmQTL). These gmQTL were further located on the Chinese Spring reference sequence map. Finally, 77 high-confidence mQTL (hcmQTL) were selected from the reference sequence-based mQTL (smQTL). Locus-specific single nucleotide polymorphism (SNP) and simple sequence repeat (SSR) markers and 17 genes responsive to FHB were then identified in the hcmQTL intervals by combined analysis of transcriptomic and proteomic data. This work may lead to a comprehensive molecular breeding platform for improving wheat resistance to FHB.
38 citations
TL;DR: The aim in this review is to aid researchers to learn quickly how to use plant nanobiotechnology for improving agricultural production and to discuss the knowledge gaps in these topics.
Abstract: Nano-enabled agriculture is an emerging hot topic. To facilitate the development of nano-enabled agriculture, reviews addressing or discussing the applications, knowledge gap, future research needs, and possible new research field of plant nanobiotechnology in agricultural production are encouraged. Here we review the following topics in plant nanobiotechnology for agriculture: 1) improving stress tolerance, 2) stress sensing and early detection, 3) targeted delivery and controlled release of agrochemicals, 4) transgenic events in non-model crop species, and 5) seed nanopriming. We discuss the knowledge gaps in these topics. Besides the use of nanomaterials for harvesting more electrons to improve photosynthetic performance, they could be used to convert nIR and UV to visible light to expand the light spectrum for photosynthesis. We discuss this approach to maintaining plant photosynthesis under light-insufficient conditions. Our aim in this review is to aid researchers to learn quickly how to use plant nanobiotechnology for improving agricultural production.
37 citations
TL;DR: One-time deep-placement fertilization could be an effective strategy for increasing grain yield and nitrogen use efficiency and lowering greenhouse-gas emissions under mechanical direct-seeded cropping systems.
Abstract: Deep placement of nitrogen fertilizer is a key strategy for improving nitrogen use efficiency. A two-year field experiment was conducted during the early rice growing seasons (March–July) of 2016 and 2017. The experimental treatments comprised two rice cultivars: Wufengyou 615 (WFY 615) and Yuxiangyouzhan (YXYZ), and three N treatments: mechanical deep placement of all fertilizers as basal dose at 10 cm soil depth (one-time deep-placement fertilization, namely OTDP fertilization); manual surface broadcast (the common farmer practice) of 40% N fertilizer at one day before sowing (basal fertilizer) followed by broadcast application of 30% each at tillering and panicle initiation stages; and no fertilizer application at any growth stage as a control. One-time deep-placement fertilization increased grain yield of both rice cultivars by 11.8%–19.6%, total nitrogen accumulation by 10.3%–13.1%, nitrogen grain production efficiency by 29.7%–31.5%, nitrogen harvest index by 27.8%–30.0%, nitrogen agronomic efficiency by 71.3%–77.2%, and nitrogen recovery efficiency by 42.4%–56.7% for both rice cultivars, compared with the multiple-broadcast treatment. One-time deep-placement fertilization reduced CH4-induced global warming potential (GWP) by 20.7%–25.3%, N2O-induced GWP by 7.2%–12.3%, and total GWP by 14.7%–22.9% for both rice cultivars relative to the multiple-broadcast treatment. The activities of glutamine synthetase and nitrate reductase were increased at both panicle-initiation and heading stages in both rice cultivars following one-time deep-placement fertilization treatment. Larger leaf area index at heading stage and more favorable root morphological traits expressed as larger total root length, mean root diameter, and total root volume per hill were also observed. One-time deep-placement fertilization could be an effective strategy for increasing grain yield and nitrogen use efficiency and lowering greenhouse-gas emissions under mechanical direct-seeded cropping systems.
TL;DR: The findings suggest that straw incorporation can increase rice yield stability through improving the resistance of rice plant growth to low PAR and reduce the coefficient of variation of rice yield.
Abstract: Straw incorporation is a global common practice to improve soil fertility and rice yield. However, the effect of straw incorporation on rice yield stability is still unknown, especially under high fertilization level conditions. Here, we reported the effect of straw returning on rice yield and yield stability under high fertilization levels in the rice–wheat system over nine years. The results showed that straw incorporation did not significantly affect the average rice yield of nine years. Straw incorporation reduced the coefficient of variation of rice yield by 25.8% and increased the sustainable yield index by 8.2%. The rice yield positively correlated with mean photosynthetically active radiation (PAR) of rice growth season and the effects of straw incorporation on rice yield depended on the PAR. Straw incorporation increased the rice yield by 5.4% in the low PAR years, whereas it did not affect the rice yield in the high PAR years. Long-term straw incorporation lowered soil bulk density but improved the soil organic matter, total N, available N, available P, and available K more strongly than straw removal. Our findings suggest that straw incorporation can increase rice yield stability through improving the resistance of rice plant growth to low PAR.
TL;DR: This review of major genetics and statistical factors affecting predictive performance as well as current progress in the application of genomic selection to rice breeding envision that integrating GS with other advanced breeding technologies such as unmanned aerial vehicles and open-source breeding platforms will further improve the efficiency and reduce the cost of breeding.
Abstract: Rice (Oryza sativa) provides a staple food source for more than half the world population. However, the current pace of rice breeding in yield growth is insufficient to meet the food demand of the ever-increasing global population. Genomic selection (GS) holds a great potential to accelerate breeding progress and is cost-effective via early selection before phenotypes are measured. Previous simulation and experimental studies have demonstrated the usefulness of GS in rice breeding. However, several affecting factors and limitations require careful consideration when performing GS. In this review, we summarize the major genetics and statistical factors affecting predictive performance as well as current progress in the application of GS to rice breeding. We also highlight effective strategies to increase the predictive ability of various models, including GS models incorporating functional markers, genotype by environment interactions, multiple traits, selection index, and multiple omic data. Finally, we envision that integrating GS with other advanced breeding technologies such as unmanned aerial vehicles and open-source breeding platforms will further improve the efficiency and reduce the cost of breeding.
TL;DR: This review will be beneficial for understanding the roles of the MRTCP-mediated regulatory network and its molecular mechanisms in plant development and stress response, and provides a theoretical basis for plant genetic improvement.
Abstract: Elaborate regulation of gene expression is required for plants to maintain normal growth, development, and reproduction. MicroRNAs (miRNAs) and transcription factors are key players that control gene expression in plant regulatory networks. The TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR (TCP) family comprises plant-specific transcription factors that contain a conserved TCP domain of 59 amino acids. Some members of this family are targeted by miR319, one of the most ancient and evolutionarily conserved miRNAs in plants. Accumulating evidence has revealed that miR319-regulated TCP (MRTCP) genes participate extensively in plant development and responses to environmental stress. In this review, the structural characteristics and classifications of TCP transcription factors and the regulatory relationships between TCP transcription factors and miRNAs are introduced. Current knowledge of the regulatory functions of MRTCP genes in multiple biological pathways including leaf development, vascular formation, flowering, hormone signaling, and response to environmental stresses such as cold, salt, and drought is summarized. This review will be beneficial for understanding the roles of the MRTCP-mediated regulatory network and its molecular mechanisms in plant development and stress response, and provides a theoretical basis for plant genetic improvement.
TL;DR: The T1DL·1VS#5 translocation line NAU1817 provides a new germplasm in wheat breeding for improvement of powdery mildew resistance, suggesting that the defence layers of the Pm67 line is tissue-differentiated.
Abstract: Powdery mildew, caused by the biotrophic fungus Blumeria graminis f. sp. tritici (Bgt), is a global disease that poses a serious threat to wheat production. To explore additional resistance gene, a wheat-Dasypyrum villosum 1 V#5 (1D) disomic substitution line NAU1813 (2n = 42) with high level of seedling resistance to powdery mildew was used to generate the recombination between chromosomes 1 V#5 and 1D. Four introgression lines, including t1VS#5 ditelosomic addition line NAU1815, t1VL#5 ditelosomic addition line NAU1816, homozygous T1DL·1VS#5 translocation line NAU1817, and homozygous T1DS·1VL#5 translocation line NAU1818 were developed from the selfing progenies of 1 V#5 and 1D double monosomic line that derived from F1 hybrids of NAU1813/NAU0686. All of them were characterized by fluorescence in situ hybridization, genomic in situ hybridization, 1 V-specific markers analysis, and powdery mildew tests at different developmental stages. A new powdery mildew resistance gene named Pm67 was physically located in the terminal bin (FL 0.70–1.00) of 1VS#5. Lines with Pm67 exhibited seedling stage immunity and tissue-differentiated reactions at adult plant stage. The sheaths, stems, and spikes of the Pm67 line were still immune, but the leaves showed a low degree of susceptibility. Microscopic observation showed that most penetration attempts were stopped in association with papillae on the sheath, and colonies cannot form conidia on the susceptible leaf of Pm67 line at adult plant stage, suggesting that the defence layers of the Pm67 line is tissue-differentiated. Thus, the T1DL·1VS#5 translocation line NAU1817 provides a new germplasm in wheat breeding for improvement of powdery mildew resistance.
TL;DR: The object is to broaden knowledge of the genetic basis of anthocyanin biosynthesis in rice and support the breeding of novel rice cultivars and to shed light on the evolutionary history of O. sativa.
Abstract: Anthocyanins are a major subclass of flavonoids that have diverse biological functions and benefit human health. In rice (Oryza sativa), the various colors shown by organs are due mainly to the accumulation of anthocyanins and are traits associated with domestication. Elucidating the genetic basis of anthocyanin biosynthesis in rice would support the engineering of anthocyanins as well as shedding light on the evolutionary history of O. sativa. We summarize recent progress in rice anthocyanin biosynthesis research, including gene cloning, biosynthetic pathway discovery, and study of the domestication process. We discuss the application of anthocyanin biosynthesis genes in rice breeding. Our object is to broaden knowledge of the genetic basis of anthocyanin biosynthesis in rice and support the breeding of novel rice cultivars.
TL;DR: This review of recent advances in pathogen-associated molecular pattern-triggered immunity, effector-tracked immunity, defense regulator-mediated immunity, and effects of nutrient elements on rice blast resistance outlines strategies used for breeding rice cultivars with improved disease resistance.
Abstract: Global food security is threatened by rice blast disease caused by the filamentous fungus Magnaporthe oryzae. An understanding of rice resistance mechanisms is fundamental to developing strategies for disease control. In this review, we summarize recent advances in pathogen-associated molecular pattern-triggered immunity, effector-triggered immunity, defense regulator-mediated immunity, and effects of nutrient elements on rice blast resistance. We outline strategies used for breeding rice cultivars with improved disease resistance. We also present the major research challenges for rice blast disease resistance and propose approaches for future investigation.
TL;DR: Current understanding of amino acids in the rhizosphere and in metabolism is summarized and their function as signal molecules and in regulating plant architecture, flowering time, and defense against abiotic stress and pathogen attack is described.
Abstract: Amino acids are essential plant compounds serving as the building blocks of proteins, the predominant forms of nitrogen (N) distribution, and signaling molecules. Plant amino acids derive from root acquisition, nitrate reduction, and ammonium assimilation. Many amino acid transporters (AATs) mediating transfer processes of amino acids have been functionally characterized in Arabidopsis, whereas the function and regulation of the vast majority of AATs in rice (Oryza sativa L.) and other crops remain unknown. In this review, we summarize the current understanding of amino acids in the rhizosphere and in metabolism. We describe their function as signal molecules and in regulating plant architecture, flowering time, and defense against abiotic stress and pathogen attack. AATs not only function in root acquisition and translocation of amino acids from source to sink organs, regulating N uptake and use efficiency, but also as transporters of non-amino acid substrates or as amino acid sensors. Several AAT genes show natural variations in their promoter and coding regions that are associated with altered uptake rate of amino acids, grain N content, and tiller number. Development of an amino acid transfer model in plants will advance the manipulation of AATs for improving rice architecture, grain yield and quality, and N-use efficiency.
TL;DR: The recent progresses of the sugar metabolism-related GMS genes and their roles during plant anther and pollen development, including callose wall and primexine formation, intine development, pollen maturation and starch accumulation, anther dehiscence, and pollen germination and tube growth are summarized.
Abstract: Sugar metabolism plays an essential role in plant male reproduction. Defects in sugar metabolism during anther and pollen development often result in genic male sterility (GMS). In this review, we summarize the recent progresses of the sugar metabolism-related GMS genes and their roles during plant anther and pollen development, including callose wall and primexine formation, intine development, pollen maturation and starch accumulation, anther dehiscence, and pollen germination and tube growth. We predict 112 putative sugar metabolic GMS genes in maize based on bioinformatics and RNA-seq analyses, and most of them have peak expression patterns during middle or late anther developmental stages. Finally, we outline the potential applications of sugar metabolic GMS genes in crop hybrid breeding and seed production. This review will deepen our understanding on sugar metabolic pathways in controlling pollen development and male fertility in plants.
TL;DR: The practice shows that target chromosome-segment substitution is a way to breeding by design and achieves the breeding goals by pyramiding target genes in the HJX74-SSSL library.
Abstract: Progress in plant breeding depends on the development of genetic resources, genetic knowledge, and breeding techniques. The core of plant breeding is the use of naturally occurring variation. At the beginning of the post-genomic era, a new concept of “breeding by design” was proposed, which aims to control all allelic variation for all genes of agronomic importance. In the past two decades, we have applied a three-step strategy for research on rice breeding by design. In the first step, we constructed a single-segment substitution line (SSSL) library using Huajingxian 74 (HJX74), an elite xian (indica) rice cultivar, as the recipient in which to assemble genes from the rice AA genome. In the second step, we identified a series of desirable genes in the SSSL library. In the third step, we designed new rice lines, and achieved the breeding goals by pyramiding target genes in the HJX74-SSSL library. This review introduces the background, concept, and strategy of breeding by design, as well as our achievements in rice breeding by design using the HJX74-SSSL platform. Our practice shows that target chromosome-segment substitution is a way to breeding by design.
TL;DR: The grain-filling rate of inferior grain in the middle spikelets was significantly decreased under high nitrogen input and high planting density conditions, particularly during the early and middle grain- filling periods, leading to the suppression of grain filling and consequent decrease in grain weight.
Abstract: Excessive use of nitrogen fertilizer and high planting density reduce grain weight in wheat. However, the effects of high nitrogen and planting density on the filling of grain located in different positions of the wheat spikelet are unknown. A two-year field experiment was conducted to investigate this question and the underlying mechanisms with respect to hormone and carbohydrate activity. Both high nitrogen application and planting density significantly increased spike density, while reducing kernel number per spike and 1000-kernel weight. However, the effects of high nitrogen and high plant density on kernel number per spike and 1000-kernel weight were different. The inhibitory effect of high nitrogen application and high planting density on kernel number per spike was achieved mainly by a reduction in kernel number per spikelet in the top and bottom spikelets. However, the decrease in 1000-kernel weight was contributed mainly by the reduced weight of grain in the middle spikelets. The grain-filling rate of inferior grain in the middle spikelets was significantly decreased under high nitrogen input and high planting density conditions, particularly during the early and middle grain-filling periods, leading to the suppression of grain filling and consequent decrease in grain weight. This effect resulted mainly from inhibited sucrose transport to and starch accumulation in inferior grain in the middle spikelets via reduction of the abscisic acid/ethylene ratio. This mechanism may explain how high nitrogen application and high planting density inhibit the grain filling of inferior wheat grain.
TL;DR: An efficient protoplast-based transformation system by optimizing conditions of protoplasts isolation and PEG-mediated transformation in S. spontaneum was developed and it shall be suitable for in vivo functional gene analysis in sugarcane.
Abstract: Sugarcane is a prominent source of sugar and ethanol production Genetic analysis for trait improvement of sugarcane is greatly hindered by its complex genome, long breeding cycle, and recalcitrance to genetic transformation The protoplast-based transient transformation system is a versatile and convenient tool for in vivo functional gene analysis; however, quick and effective transformation systems are still lacking for sugarcane Here, we developed an efficient protoplast-based transformation system by optimizing conditions of protoplasts isolation and PEG-mediated transformation in S spontaneum The yield of viable protoplasts was approximately 126 × 107 per gram of leaf material, and the transformation efficiency of 8019% could be achieved under the optimized condition Furthermore, using this approach, the nuclear localization of an ABI5-like bZIPs transcription factor was validated, and the promoter activity of several putative DNase I hypersensitive sites (DHSs) was assessed The results indicated this system can be conveniently applied to protein subcellular localization and promoter activity assays A highly efficient S spontaneum mesophyll cell protoplast isolation and transient transformation method was developed, and it shall be suitable for in vivo functional gene analysis in sugarcane
TL;DR: A DNA marker for the G628W allele was developed that accurately and robustly distinguished homozygous from heterozygous segregants and further demonstrates the feasibility of CRISPR/Cas9-mediated gene editing in creating novel genetic variation for crop breeding.
Abstract: Weeds and weedy rice plague commercial rice fields in many countries. Developing herbicide-tolerance rice is the most efficient strategy to control weed proliferation. CRISPR/Cas9-mediated gene editing, which generates small InDels and nucleotide substitutions at and around target sites using error-prone non-homologous end joining DNA repairing, has been widely adopted for generation of novel crop germplasm with a wide range of genetic variation in important agronomic traits. We created a novel herbicide-tolerance allele in rice by targeting the acetolactate synthase (OsALS) gene using CRISPR/Cas9-mediated gene editing. The novel allele (G628W) arose from a G-to-T transversion at position 1882 of OsALS and conferred a high level of herbicide tolerance. Transgene-free progeny carrying homozygous G628W allele were identified and showed agronomic performance similar to that of wild-type plants, suggesting that the G628W allele is a valuable resource for developing elite rice varieties with strong herbicide tolerance. To promote use of the G628W allele and to accelerate introgression and/or pyramiding of the G628W allele with other elite alleles, we developed a DNA marker for the G628W allele that accurately and robustly distinguished homozygous from heterozygous segregants. Our result further demonstrates the feasibility of CRISPR/Cas9-mediated gene editing in creating novel genetic variation for crop breeding.
TL;DR: Investigation of the influence of RNHD on rice yield, fertilizer 15N fate, and root growth in a double-rice cropping system in China resulted in similar yield and biomass production as well as plant N uptake.
Abstract: Rational nitrogen (N) application can greatly increase rice (Oryza sativa L.) yield. However, excessive N input can lead not only to low N use efficiency (NUE) but also to severe environmental pollution. Reducing N application rate with a higher planting density (RNHD) is recommended to maintain rice yield and improve NUE. The effects of RNHD on fertilizer N fate and rice root growth traits remain unclear. We accordingly conducted a two-year field experiment to investigate the influence of RNHD on rice yield, fertilizer 15N fate, and root growth in a double-rice cropping system in China. In comparison with the conventional practice of high N application with sparse planting, RNHD resulted in similar yield and biomass production as well as plant N uptake. RNHD increased agronomic NUEs by 23.3%–31.9% (P
TL;DR: Existing data on senescence-related transcriptome studies and gene regulatory network could effectively be used for functional study in developing nitrogen efficient wheat varieties.
Abstract: Wheat leaf senescence is a developmental process that involves expressional changes in thousands of genes that ultimately impact grain protein content (GPC), grain yield (GY), and nitrogen use efficiency. The onset and rate of senescence are strongly influenced by plant hormones and environmental factors e.g. nitrogen availability. At maturity, decrease in nitrogen uptake could enhance N remobilization from leaves and stem to grain, eventually leading to leaf senescence. Early senescence is related to high GPC and somewhat low yield whereas late senescence is often related to high yield and somewhat low GPC. Early or late senescence is principally regulated by up and down-regulation of senescence associated genes. Integration of external and internal factors together with genotypic variation influence senescence associated genes in a developmental age dependent manner. Although regulation of genes involved in senescence has been studied in rice, Arabidopsis, maize, and currently in wheat, there are genotype-specific variations yet to explore. A major effort is needed to understand the interaction of positive and negative senescence regulators in determining the onset of senescence. In wheat, increasing attention has been paid to understand the role of positive senescence regulator, e.g. GPC-1, regulated gene network during early senescence time course. Recently, gene regulatory network involved early to late senescence time course revealed important senescence regulators. However, the known negative senescence regulator TaNAC-S gene has not been extensively studied in wheat and little is known about its value in breeding. Existing data on senescence-related transcriptome studies and gene regulatory network could effectively be used for functional study in developing nitrogen efficient wheat varieties.
TL;DR: It is concluded that GhPAS1, a bHLH transcription factor, regulates plant development and architecture in cotton, and may help breeders and researchers develop cotton cultivars with desirable agronomic characteristics.
Abstract: Cotton (Gossypium spp.) is the most important natural textile fiber crop in the world. The ideal plant architecture of cotton is suitable for mechanical harvesting and productivity in modern agricultural production. However, cotton genes regulating plant development and architecture have not been fully identified. We identified a basic helix-loop-helix (bHLH) transcription factor, GhPAS1 (PAGODA1 SUPPRESSOR 1) in G. hirsutum (Upland cotton). GhPAS1 was located in the nucleus and showed a strong transcription activation effect. Tissue-specific expression patterns showed that GhPAS1 was highly expressed in floral organs, followed by high expression in early stages of ovule development and rapid fiber elongation. GhPAS1 overexpression in Arabidopsis and BRZ (brassinazole, BR biosynthesis inhibitor) treatment indicated that GhPAS1 positively regulates and responds to the BR (brassinosteroid) signaling pathway and promotes cell elongation. GhPAS1 overexpression in Arabidopsis mediated plant development in addition to increasing plant biomass. Virus-induced gene silencing of GhPAS1 indicated that down-regulation of GhPAS1 inhibited cotton growth and development, as plant height, fruit branch length, and boll size of silenced plants were lower than in control plants. Fiber length and seed yield were also lower in silenced plants. We conclude that GhPAS1, a bHLH transcription factor, regulates plant development and architecture in cotton. These findings may help breeders and researchers develop cotton cultivars with desirable agronomic characteristics.
TL;DR: Genomic selection (GS) by incorporating SNP associations detected from GWAS is a promising tool for improving FER resistance in maize with moderate prediction accuracies when the training and validation sets were closely related.
Abstract: Fusarium ear rot (FER) is a destructive maize fungal disease worldwide. In this study, three tropical maize populations consisting of 874 inbred lines were used to perform genome-wide association study (GWAS) and genomic prediction (GP) analyses of FER resistance. Broad phenotypic variation and high heritability for FER were observed, although it was highly influenced by large genotype-by-environment interactions. In the 874 inbred lines, GWAS with general linear model (GLM) identified 3034 single-nucleotide polymorphisms (SNPs) significantly associated with FER resistance at the P-value threshold of 1 × 10−5, the average phenotypic variation explained (PVE) by these associations was 3% with a range from 2.33% to 6.92%, and 49 of these associations had PVE values greater than 5%. The GWAS analysis with mixed linear model (MLM) identified 19 significantly associated SNPs at the P-value threshold of 1 × 10−4, the average PVE of these associations was 1.60% with a range from 1.39% to 2.04%. Within each of the three populations, the number of significantly associated SNPs identified by GLM and MLM ranged from 25 to 41, and from 5 to 22, respectively. Overlapping SNP associations across populations were rare. A few stable genomic regions conferring FER resistance were identified, which located in bins 3.04/05, 7.02/04, 9.00/01, 9.04, 9.06/07, and 10.03/04. The genomic regions in bins 9.00/01 and 9.04 are new. GP produced moderate accuracies with genome-wide markers, and relatively high accuracies with SNP associations detected from GWAS. Moderate prediction accuracies were observed when the training and validation sets were closely related. These results implied that FER resistance in maize is controlled by minor QTL with small effects, and highly influenced by the genetic background of the populations studied. Genomic selection (GS) by incorporating SNP associations detected from GWAS is a promising tool for improving FER resistance in maize.
TL;DR: The establishment of “the third-generation hybrid rice technology” enables efficient propagation of the pure NMS lines in commercial scale and will bring a big leap forward in hybrid rice production.
Abstract: The breeding and large-scale application of hybrid rice contribute significantly to the food supply worldwide. Currently, hybrid seed production uses cytoplasmic male sterile (CMS) lines or photoperiod/thermo-sensitive genic male sterile (PTGMS) lines as female parent. Despite huge successes, both systems have intrinsic problems. CMS systems are mainly restricted by the narrow restorer resources that make it difficult to breed superior hybrids, while PTGMS systems are limited by conditional sterility of the male sterile lines that makes the propagation of both PTGMS seeds and hybrid seeds vulnerable to unpredictable climate changes. Recessive nuclear male sterile (NMS) lines insensitive to environmental conditions are widely distributed and are ideal for hybrid rice breeding and production, but the lack of effective ways to propagate the pure NMS lines in a large scale renders it impossible to use them for hybrid rice production. The development of “the third-generation hybrid rice technology” enables efficient propagation of the pure NMS lines in commercial scale. This paper discusses the establishment of “the third-generation hybrid rice technology” and further innovations. This new technology breaks the limitations of CMS and PTGMS systems and will bring a big leap forward in hybrid rice production.
TL;DR: It is suggested that heavy soil drying practice during the mid-to-late grain filling stage of the main crop is effective for reducing YLoss of the ratoon crop in a mechanized rice ratooning system.
Abstract: Yield loss (YLoss) in the ratoon crop due to crushing damage to left stubble from mechanical harvesting of the main crop is a constraint for wide adoption of mechanized rice ratooning technology. Soil drying before the harvest of the main crop has been proposed to overcome this problem. The objective of this study was to determine the effect of soil drying during the mid-to-late grain filling stage of the main crop on grain yield of the ratoon crop in a mechanized rice ratooning system. Field experiments were conducted to compare YLoss between light (LD) and heavy (HD) soil drying treatments in Hubei province, central China in 2017 and 2018. YLoss was calculated as the percentage of yield reduction in the ratoon crop with the main crop harvested mechanically, relative to the grain yield of the ratoon crop with the main crop harvested manually. In comparison with LD, soil hardness was increased by 42.8%–84.7% in HD at the 5–20 cm soil depth at maturity of the main crop. Soil hardness at 5 and 10 cm depths reached respectively 4.05 and 7.07 kg cm−2 in HD. Soil drying treatment did not significantly affect the grain yield of the main crop. Under mechanical harvesting of the main crop, HD increased the grain yield of the ratoon crop by 9.4% relative to LD. Consequently, YLoss was only 3.4% in HD, in contrast to 16.3% in LD. The differences in grain yield and YLoss between the two soil drying treatments were explained mainly by panicles m−2, which was increased significantly by HD in the track zone of the ratoon crop compared with LD. These results suggest that heavy soil drying practice during the mid-to-late grain filling stage of the main crop is effective for reducing YLoss of the ratoon crop in a mechanized rice ratooning system.
TL;DR: In this article, targeted editing of AMS homologs in soybean by CRISPR/Cas9 technology for the first time to generate stable male-sterile lines was proposed.
Abstract: Soybean [Glycine max (L.) Merr.] provides a rich source of plant protein and oil worldwide. The commercial use of transgenic technology in soybean has become a classical example of the application of biotechnology to crop improvement. Although genetically modified soybeans have achieved commercial success, hybrid soybean breeding is also a potential way to increase soybean yield. Soybean cytoplasmic male-sterile (CMS) lines have been used in three-line hybrid breeding systems, but their application to exploiting soybean heterosis has been limited by rare germplasm resource of sterile lines. The generation of various genetic diversity male-sterile soybean lines will help to overcome the shortcoming. In this study, we used targeted editing of AMS homologs in soybean by CRISPR/Cas9 technology for the first time to generate stable male-sterile lines. Targeted editing of GmAMS1 resulted in a male-sterile phenotype, while editing of GmAMS2 failed to produce male-sterile lines. GmAMS1 functions not only in the formation of the pollen wall but also in the controlling the degradation of the soybean tapetum. CRISPR/Cas9 technology could be used to rapidly produce stable male-sterile lines, providing new sterile-line materials for soybean hybrid breeding systems.