Crop Journal最新文献

The Triticum-Aegilops complex provides ideal models for the study of polyploidization, and mitochondrial genomes (mtDNA) can be used to trace cytoplasmic inheritance and energy production following polyploidization. In this study, gapless mitochondrial genomes for 19 accessions of five Triticum or Aegilops species were assembled. Comparative genomics confirmed that the BB-genome progenitor donated mtDNA to tetraploid T. turgidum (genome formula AABB), and that this mtDNA was then passed on to the hexaploid T. aestivum (AABBDD). T urartu (AA) was the paternal parent of T. timopheevii (AAGG), and an earlier Ae. tauschii (DD) was the maternal parent of Ae. cylindrica (CCDD). Genic sequences were highly conserved within species, but frequent rearrangements and nuclear or chloroplast DNA insertions occurred during speciation. Four highly variable mitochondrial genes (atp6, cob, nad6, and nad9) were established as marker genes for Triticum and Aegilops species identification. The BB/GG-specific atp6 and cob genes, which were imported from the nuclear genome, could facilitate identification of their diploid progenitors. Genic haplotypes and repeat-sequence patterns indicated that BB was much closer to GG than to Ae. speltoides (SS). These findings provide novel insights into the polyploid evolution of the Triticum/Aegilops complex from the perspective of mtDNA, advancing understanding of energy supply and adaptation in wheat species.

Autophagy is an evolutionarily conserved degradation pathway of lysosomes (in mammals) and vacuoles (in yeasts and plants) from lower yeasts to higher mammals. It wraps unwanted organelles and damaged proteins in a double-membrane structure to transport them to vacuoles for degradation and recycling. In plants, autophagy functions in adaptation to the environment and maintenance of growth and development. This review systematically describes the autophagy process, biological functions, and regulatory mechanisms occurring during plant growth and development and in response to abiotic stresses. It provides a basis for further theoretical research and guidance of agricultural production.

Genomic prediction (GP) in plant breeding has the potential to predict and identify the best-performing hybrids based on the genotypes of their parental lines. In a GP experiment, 34 elite inbred lines were selected to make 285 single-cross hybrids in a partial-diallel cross design. These lines represented a mini-core collection of Chinese maize germplasm and comprised 18 inbred lines from the Stiff Stalk heterotic group and 16 inbred lines from the Non-Stiff Stalk heterotic group. The parents were genotyped by sequencing and the 285 hybrids were phenotyped for nine yield and yield-related traits at two locations in the summer sowing area (SUS) and three locations in the spring sowing area (SPS) in the main maize-producing regions of China. Multiple GP models were employed to assess the accuracy of trait prediction in the hybrids. By ten-fold cross-validation, the prediction accuracies of yield performance of the hybrids estimated by the genomic best linear unbiased prediction (GBLUP) model in SUS and SPS were 0.51 and 0.46, respectively. The prediction accuracies of the remaining yield-related traits estimated with GBLUP ranged from 0.49 to 0.86 and from 0.53 to 0.89 in SUS and SPS, respectively. When additive, dominance, epistasis effects, genotype-by-environment interaction, and multi-trait effects were incorporated into the prediction model, the prediction accuracy of hybrid yield performance was improved. The ratio of training to testing population and size of training population optimal for yield prediction were determined. Multiple prediction models can improve prediction accuracy in hybrid breeding.

Powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt) is a destructive wheat disease. Although it can be easily overcome by deployment of resistance genes, the resistance is often quickly compromised by pathogen virulence. Thus, exploration and characterization of new resistance genes is always ongoing. Line NJ3946 derived from a cross of einkorn wheat accessions TA2032 and M389 showed resistance to powdery mildew. Inheritance analysis of an F₂ population derived from a cross of NJ3946 and M389 suggested that the resistance was conferred by a dominant allele. With polymorphic markers identified through bulked segregant analysis (BSA), this gene was mapped to a novel locus on chromosome 3A, and was designated as PmNJ3946. Bulked segregant RNA-seq analysis (BSR-seq) was conducted to obtain more closely linked markers, which allowed delimitation of the PMNJ3946 locus to a 0.9 cM interval covering a physical distance of less than 1 Mb. PMNJ3946 was flanked by Xwgrc5153 and SNP-derived marker CHS21_3A008915069, and co-segregated with SNP-derived markers CHS21_3A008939814 and CHS21_3A008943175. The PmNJ3946 discovery expands the diversity of powdery mildew resistance genes and is useful for wheat breeding.

Gibberellin (GA) functions in plant growth and development. However, genes involved in the biosynthesis and regulation of GA in crop plants are poorly understood. We isolated the mutant gad5-1 (GA-Associated Dwarf 5), characterized by dwarfing, short internodes, and dark green and short leaves. Map-based gene cloning and allelic verification confirmed that ZmGAD5 encodes ent-kaurenoic acid oxidase (KAO), which catalyzes KA (ent-kaurenoic acid) to GA12 conversion during GA biosynthesis in maize. ZmGAD5 is localized to the endoplasmic reticulum and is present in multiple maize organs. In gad5-1, the expression of ZmGAD5 is severely reduced, and the levels of the direct substrate of KAO, KA, is increased, leading to a reduction in GA content. The abnormal phenotype of gad5-1 was restored by exogenous application of GA₃. The biomass, plant height, and levels of GA₁₂ and GA₃ in transgenic Arabidopsis overexpressing ZmGAD5 were increased in comparison with the corresponding controls Col-0. These findings deepen our understanding of genes involved in GA biosynthesis, and could lead to the development of maize lines with improved architecture and higher planting-density tolerance.

Trichomes are specialized structures that originate from epidermal cells of organs in higher plants. The cotton fiber is a unique single-celled trichome that elongates from the seed coat epidermis. Cotton (Gossypium hirsutum) fibers and trichomes are models for cell differentiation. In an attempt to elucidate the intercellular factors that regulate fiber and trichome cell development, we identified a plasmodesmal β-1,3-glucanase gene (designated GhPdBG) controlling the opening and closing of plasmodesmata in cotton fibers. Structural and evolutionary analysis showed haplotypic variation in the promoter region of the GhPdBG gene among 352 cotton accessions, but high conservation in the coding region. GhPdBG was expressed predominantly in cotton fibers and localized to plasmodesmata (PD). Expression patterns of PdBG that corresponded to PD permeability were apparent during fiber development in G. hirsutum and G. barbadense. The PdBG-mediated opening-closure of PD appears to be involved in fiber development and may account for the contrasting fiber traits of these two species. Ectopic expression of GhPdBG revealed that it functions in regulating fiber and trichome length and/or density by modulating plasmodesmatal permeability. This finding suggests that plasmodesmal targeting of GhPdBG, as a switch of intercellular channels, regulates single-celled fiber and trichome development in cotton.

Wheat resistance to Fusarium head blight (FHB) has often been associated with some undesirable agronomic traits. To study the relationship between wheat FHB resistance and agronomic traits, we constructed a linkage map of single nucleotide polymorphisms (SNPs) using an F_6:8 population from G97252W × G97380A. The two hard winter wheat parents showed contrasts in FHB resistance, plant height (HT), heading date (HD), spike length (SL), spike compactness (SC), kernel number per spike (KNS), spikelet number per spike (SNS), thousand-grain weight (TGW) and grain size (length and width). Quantitative trait locus (QTL) mapping identified one major QTL (QFhb.hwwg-2DS) on chromosome arm 2DS for the percentage of symptomatic spikelets (PSS) in the spike, deoxynivalenol (DON) content and Fusarium damaged kernel (FDK). This QTL explained up to 71.8% of the phenotypic variation for the three FHB-related traits and overlapped with the major QTL for HT, HD, SL, KNS, SNS, TGW, and grain size. QTL on chromosome arms 2AL, 2DS, 3AL and 4BS were significant for the spike and grain traits measured. G97252W contributed FHB resistance and high SNS alleles at QFhb.hwwg-2DS, high KNS alleles at the QTL on 2AL and 2DS, and high TGW and grain size alleles at QTL on 3AL; whereas G97380A contributed high TGW and grain size alleles at the QTL on 2AL and 2DS, respectively, and the high KNS allele at the 4BS QTL. Combining QFhb.hwwg-2DS with positive alleles for spike and grain traits from other chromosomes may simultaneously improve FHB resistance and grain yield in new cultivars.

Stem rust, caused by Puccinia graminis f. sp. tritici (Pgt), threatens global wheat production. Development of cultivars with increased resistance to stem rust by identification, mapping, and deployment of resistance genes is the best strategy for controlling the disease. In this study, we performed fine mapping and characterization of the all-stage stem rust resistance (Sr) gene Sr8155B1 from the durum wheat line 8155-B1. In seedling tests of biparental populations, Sr8155B1 was effective against six Chinese Pgt races tested. In a segregating population of 5060 gametes, Sr8155B1 was mapped to a 0.06-cM region flanked by markers Pku2772 and Pku43365, corresponding to 1.5- and 2.7-Mb regions in the Svevo and Chinese Spring reference genomes. Both regions include several typical nucleotide-binding leucine-rich repeat (NLR) and protein kinase genes that represent candidate genes. Among them, three NLR genes and three receptor-like protein kinases were highly polymorphic between the parental lines and their transcripts were upregulated in the homozygous resistant line TdR2 relative to its susceptible sister line TdS4. Four markers (Pku2772, Pku43365, Pku2950, and Pku3721) developed in this study, together with seedling resistance responses, correctly predicted Sr8155B1 absence or presence in 78 tetraploid wheat genotypes tested. The presence of Sr8155B1 in tetraploid wheat accessions CItr 14916, PI 197492, and PI 197493 was confirmed by mapping in three F₂ populations. The genetic map and linked markers developed in this study may accelerate the deployment of Sr8155B1-mediated resistance in wheat breeding programs.

Carotenoid biosynthesis and accumulation are important in determining nutritional and commercial value of crop products. Yellow pigmentation of mature kernels caused by carotenoids is considered a vital quality trait in foxtail millet, an ancient and widely cultivated cereal crop across the world. Genomic regions associated with yellow pigment content (YPC), lutein and zeaxanthin in foxtail millet grains were identified by genome-wide association analysis (GWAS), and SiPSY1 (Phytoene synthase 1 which regulates formation of the 40-carbon backbone of carotenoids) was confirmed as the main contributor to all three components by knockout and overexpression analysis. SiPSY1 was expressed in seedlings, leaves, panicles, and mature seeds, and was subcellularly localized to chloroplasts. Transcription of SiPSY1 in 15 DAP immature grains was responsible for YPC in mature seeds. Selection of SiPSY1 combined with increased YPC in mature grains during domestication of foxtail millet was confirmed. Haplotype analysis suggested that expression level of SiPSY1 could be a selection target for future breeding programs, and a KASP marker was developed for selection of favorable SiPSY1 alleles in breeding. The results of this work will benefit nutritional and commercial improvement of foxtail millet varieties, as well as other cereal crops.

Maize (Zea mays L.) is an indispensable crop worldwide for food, feed, and bioenergy production. Fusarium verticillioides (F. verticillioides) is a widely distributed phytopathogen and incites multiple destructive diseases in maize: seedling blight, stalk rot, ear rot, and seed rot. As a soil-, seed-, and airborne pathogen, F. verticillioides can survive in soil or plant residue and systemically infect maize via roots, contaminated seed, silks, or external wounds, posing a severe threat to maize production and quality. Infection triggers complex immune responses: induction of defense-response genes, changes in reactive oxygen species, plant hormone levels and oxylipins, and alterations in secondary metabolites such as flavonoids, phenylpropanoids, phenolic compounds, and benzoxazinoid defense compounds. Breeding resistant maize cultivars is the preferred approach to reducing F. verticillioides infection and mycotoxin contamination. Reliable phenotyping systems are prerequisites for elucidating the genetic structure and molecular mechanism of maize resistance to F. verticillioides. Although many F. verticillioides resistance genes have been identified by genome-wide association study, linkage analysis, bulked-segregant analysis, and various omics technologies, few have been functionally validated and applied in molecular breeding. This review summarizes research progress on the infection cycle of F. verticillioides in maize, phenotyping evaluation systems for F. verticillioides resistance, quantitative trait loci and genes associated with F. verticillioides resistance, and molecular mechanisms underlying maize defense against F. verticillioides, and discusses potential avenues for molecular design breeding to improve maize resistance to F. verticillioides.