Hatching and development of maize cyst nematode Heterodera zeae infecting different plant hosts

The occurrence, distribution, and rapid molecular detection technology of Heterodera zeae Koshy et al. 1971, have been reported in China. We explored the biological characteristics of H. zeae sampled in Henan Province, China to understand its interaction with plants. Cysts and second-stage juveniles(J2s) were identified under an optical and scanning electron microscope, internal transcribed spacer(ITS) phylogenetic tree, and sequence characterized amplified region(SCAR)-PCR analyses. The optimum hatching temperatures of H. zeae were 30°C and 28°C, with cumulative hatching rates of 16.5 and 16.1%, respectively, at 30 days post-hatching(dph). The hatching rate of H. zeae eggs was improved by 20-and 50-time maize soil leachate and root juice, and 10-time root exudates. The hatching rate in 10-time root exudates was the highest(25.9%). The 10-time root exudates of maize and millet produced the highest hatching rate at 30 dph(25.9 and 22.9%, respectively), followed by wheat(19.9%), barley(18.3%), and rice(17.6%). Heterodera zeae developed faster in maize than in other crops. Fourth-stage juveniles(J4s) were detected in maize roots 8 days post-inoculation(dpi) at 28°C but not in other crops. Combined with hatching tests, the Huang–Huai–Hai summer maize region and the south and central-southwest mountainous maize areas are highly suitable for H. zeae in China. This is the first systematically study of the hatching and infection characteristics on different plant hosts of corn cyst nematode H. zeae in temperate regions. This study laid a theoretical foundation for the rapid spread and high environmental adaptability of corn cyst nematode.

The cytosolic isoform of triosephosphate isomerase,ZmTPI4,is required for kernel development and starch synthesis in maize(Zea mays L.)

Triosephosphate isomerase(TPI)is an enzyme that functions in plant energy production,accumulation,and conversion.To understand its function in maize,we characterized a maize TPI mutant,zmtpi4.In comparison to the wild type,zmtpi4 mutants showed altered ear development,reduced kernel weight and starch content,modified starch granule morphology,and altered amylose and amylopectin content.Protein,ATP,and pyruvate contents were reduced,indicating ZmTPI4 was involved in glycolysis.Although subcellular localization confirmed ZmTPI4 as a cytosolic rather than a plastid isoform of TPI,the zmtpi4 mutant showed reduced leaf size and chlorophyll content.Overexpression of ZmTPI4 in Arabidopsis led to enlarged leaves and increased seed weight,suggesting a positive regulatory role of ZmTPI4 in kernel weight and starch content.We conclude that ZmTPI4 functions in maize kernel development,starch synthesis,glycolysis,and photosynthesis.

Molecular genetic and genomic analysis of wheat milling and end-use traits in China:Progress and perspectives

Wheat is the most widely cultivated staple food crop, and multiple types of food derivatives are processed and consumed globally. Wheat grain quality(WGQ) is central to food processing and nutritional value, and is a decisive factor for consumer acceptance and commercial value of wheat cultivars. Hence, improvement in WGQ traits is top priority for both conventional and molecular wheat breeding. In this review we will focus on two important WGQ traits, grain milling and end-use, and will summarize recent progress in China. Chinese scientists have invested substantial effort in molecular genetic and genomic analysis of these traits and their effects on end-use properties. The insights and resources generated have contributed to the understanding and improvement of these traits. As high-quality genomics information and powerful genome engineering tools are becoming available for wheat, more fundamental breakthroughs in dissecting the molecular and genomic basis of WGQ are expected. China will strive to make further significant contributions to the study and improvement of WGQ in the genomics era.

Assessment of the individual and combined effects of Rht8 and Ppd-D1a on plant height, time to heading and yield traits in common wheat

Grain yield in cereal crops is a complex trait controlled by multiple genes and influenced by developmental processes and environment. Here we report the effects of alleles Rht8 and Ppd-D1 a on plant height, time to heading, and grain yield and its component traits. Association analysis and quantitative trait locus mapping using phenotypic data from 15 environments led to the following conclusions. First, both Rht8 and Ppd-D1 a reduce plant height. However, Ppd-D1 a but not Rht8 causes earlier heading.Second, both Rht8 and Ppd-D1 a promote grain yield and affect component traits. Their combined effects are substantially larger than those conferred by either allele alone.Third, promotion of grain yield by Rht8 and Ppd-D1 a is through increasing fertile spikelet number. We speculate that Rht8 and Ppd-D1 a act independently and additively in control of plant height, grain yield and yield component. Combination of the two alleles is desirable for adjusting plant height and enhancing grain yield and abiotic stress tolerance.

Comparative QTL analysis of maize seed artificial aging between an immortalized F_2 population and its corresponding RILs

Seed aging decreases the quality and vigor of crop seeds,thereby causing substantial agricultural and economic losses in crops.To identify genetic differences in seed aging between homozygotes and heterozygotes in maize,the seeds of a set of recombinant inbred lines(RILs) and an immortalized F_2(IF_2) population were subjected to artificial aging treatments for 0,2,3,and 4 days under 45℃ and 85%relative humidity and seed vigor was then evaluated in a field experiment.Seed vigor of all entries tested decreased sharply with longer aging treatment and seed vigor decreased more slowly in heterozygotes than in homozygotes.Forty-nine QTL were detected for four measured seed vigor traits in the RIL(28QTL) and IF_2(21 QTL) populations.Only one QTL,qGP5,was detected in both populations,indicating that the genes involved in anti-aging mechanisms differed between inbred lines and hybrids.Several QTL were identified to be responsible for multiple seed vigor traits simultaneously in the RIL and IF_2 populations under artificial aging conditions.These QTL may include major genes for seed vigor or seed aging.QTL qVI4 b and qGE3 a detected in the RIL population coincided with genes ZmLOX1 and ZmPLD1 in the same respective chromosomal regions.These QTL would be useful for screening for anti-aging genes in maize breeding.

Grain yield and water use of winter wheat as affected by water and sulfur supply in the North China Plain

Water shortage has threatened sustainable development of agriculture globally as well as in the North China Plain（NCP）.Irrigation,as the most effective way to increase food production in dry land,may not be readily available in the situation of drought.One of the alternatives is to supply plants with enough nutrients so that they can be more sustainable to the water stress.The objective of this study was to explore effects of irrigation and sulphur（S）application on water consumption,dry matter accumulation（DMA）,and grain yield of winter wheat in NCP.Three irrigation regimes including no irrigation（rainfed,I0）during the whole growth period,once irrigation only at jointing stage（90 mm,I1）,and twice respective irrigation at jointing and anthesis stages（90 mm plus 90 mm,I2）,and two levels of S application including 0S0and 60 kg ha^–1（S60）were designed in the field experiment in NCP.Results showed that increasing irrigation times significantly increased mean grain yield of wheat by 12.5–23.7%and nitrogen partial factor productivity（NPFP）by 21.2–45.0%in two wheat seasons,but markedly decreased crop water use efficiency（YWUE）.Furthermore,S supply 60 kg ha^–1 significantly increased mean grain yield,YWUE,IWUE and NPFP by 5.6,6.1,23.2,and 5.6%（across two wheat seasons）,respectively.However,we also found that role of soil moisture prior to S application was one of important greater factors on improving the absorption and utilization of storage water and nutrients of soil.Thus,water supply is still the most important factor to restrict the growth of wheat in the present case of NCP,supplying 60 kg ha^–1 S with once irrigation 90 mm at the jointing stage is a relatively appropriate recommended combination to improve grain yield and WUE of wheat when saving water resources is be considered in irrigated wheat farmlands of NCP.

The effect of elevating temperature on the growth and development of reproductive organs and yield of summer maize

Compared to other crops,maize production demands relatively high temperatures.However,temperatures exceeding 35℃lead to adverse effects on maize yield.High temperatures(≥35℃)are consistently experienced by summer maize during its reproductive growth stage in the North China Plain,which is likely to cause irreversible crop damage.This study investigated the effects of elevating temperature(ET)treatment on the yield component of summer maize,beginning at the 9th unfolding leaf stage and ending at the tasseling stage.Results demonstrated that continuous ET led to a decrease in the elongation rate and activity of silks and an elongated interval between anthesis and silking stages,and eventually decreased grain number at ear tip and reduced yield.Although continuous ET before tasseling damaged the anther structure,reduced pollen activity,delayed the start of the pollen shedding stage,and shortened the pollen shedding time,it was inferred,based on phenotypical and physiological traits,that continuous ET after the 9th unfolding leaf stage influenced ears and therefore may have more significant impacts.Overall,when maize plants were exposed to ET treatment in the ear reproductive development stage,the growth of ears and tassels was blocked,which increased the occurrence of barren ear tips and led to large yield losses.

Single-cell RNA sequencing of meiocytes and microspores reveals the involvement of the Rf4 gene in redox homeostasis of CMS-C maize

Normal microsporogenesis is determined by both nuclear and mitochondrial genes. In maize C-type cytoplasmic male sterility, it is unclear how the development of meiocytes and microspores is affected by the mitochondrial sterility gene and the nuclear restorer gene. In this study, we sequenced the transcriptomes of single meiocytes(tetrad stage) and early mononucleate microspores from sterile and restorer lines. The numbers of expressed genes varied in individual cells and fewer than half of the expressed genes were common to the same cell types. Four comparisons revealed 3379 differentially expressed genes(DEGs), with 277 putatively associated with mitochondria, 226 encoding transcription factors,and 467 possibly targeted by RF4. KEGG analysis indicated that the DEGs in the two lines at the tetrad stage were involved predominantly in carbon metabolism and in amino acid biosynthesis and metabolism, whereas the DEGs during the transition from the tetrad stage to the early mononucleate stage were associated mostly with regulation of protein metabolism, fatty acid metabolism, and anatomical structure morphogenesis. Thus, meiocyte and microspore development was affected by the surrounding cells and the restorer gene, and the restorer gene helped restore the redox homeostasis of microspores and the normal cellular reconstruction during the transition.

Identification and characterization of FpRco1 in regulating vegetative growth and pathogenicity based on T-DNA insertion in Fusarium pseudograminearum

Fusarium pseudograminearum is a devastating pathogen that causes Fusarium crown rot(FCR)in wheat and poses a significant threat to wheat production in terms of grain yield and quality.However,the mechanism by which F.pseudograminearum infects wheat remains unclear.In this study,we aimed to elucidate these mechanisms by constructing a T-DNA insertion mutant library for the highly virulent strain WZ-8A of F.pseudograminearum.By screening this mutant library,we identified nine independent mutants that displayed impaired pathogenesis in barley leaves.Among these mutants,one possessed a disruption in the gene FpRCO1 that is an ortholog of Saccharomyces cerevisiae RCO1,encoding essential component of the Rpd3S histone deacetylase complex in F.pseudograminearum.To further investigate the role of FpRCO1 in F.pseudograminearum,we employed a split-marker approach to knock out FpRCO1 in F.pseudograminearum WZ-8A.FpRCO1 deletion mutants exhibit reduced vegetative growth,conidium production,and virulence in wheat coleoptiles and barley leaves,whereas the complementary strain restores these phenotypes.Moreover,under stress conditions,the FpRCO1 deletion mutants exhibited increased sensitivity to NaCl,sorbitol,and SDS,but possessed reduced sensitivity to H_(2)O_(2)compared to these characteristics in the wild-type strain.RNA-seq analysis revealed that deletion of FpRCO1 affected gene expression(particularly the downregulation of TRI gene expression),thus resulting in significantly reduced deoxynivalenol(DON)production.In summary,our findings highlight the pivotal role of FpRCO1 in regulating vegetative growth and development,asexual reproduction,DON production,and pathogenicity of F.pseudograminearum.This study provides valuable insights into the molecular mechanisms underlying F.pseudograminearum infection in wheat and may pave the way for the development of novel strategies to combat this devastating disease.

Distribution and accumulation of zinc and nitrogen in wheat grain pearling fractions in response to foliar zinc and soil nitrogen applications

Increasing zinc(Zn)concentration in wheat grain is important to minimize human dietary Zn deficiency.This study aimed to investigate the effect of foliar Zn and soil nitrogen(N)applications on the accumulation and distribution of N and Zn in grain pearling fractions,N remobilization,and the relationships between nutrient concentration in the vegetative tissues and grain or its fractions in two cropping years in the North China Plain.The results showed a progressive decrease in N and Zn concentrations from the outer to the inner parts of grain,with most of the accumulation in the core endosperm.Foliar Zn application significantly increased N concentration in the pericarp,and soil N application increased N concentration in each grain fraction.Both treatments significantly increased core endosperm Zn concentration.Foliar Zn had no effect on grain N and Zn distribution.Soil N application made N concentrated in the aleurone,promoted Zn translocation to the core endosperm and also increased N remobilization and its efficiency from the shoot to the grain,but no improved contribution to grain was found.N concentration in grain and its fractions were positively correlated with N in vegetative organs at anthesis and maturity,while positive correlations were obtained between N concentration in the pericarp and progressive central area of the endosperm and Zn concentration in the core endosperm.Thus,foliar Zn and soil N applications effectively increased yield and N and Zn concentrations in the wheat grain,particularly in the endosperm,and could be promising strategies to address Zn deficiency.

Characterization and map-based cloning of miniature2-m1, a gene controlling kernel size in maize

Kernel development plays an important role in determining kernel size in maize.Here we present the cloning and characterization of a maize gene,nitrate transporter1.5(NRT1.5),which controls small kernel phenotype by playing an important role in kernel development.A novel recessive small kernel mutant miniature2-m1(mn2-m1)was isolated from self-pollinated progenies of breeding materials.The mutant spontaneously showed small kernel character arresting both embryo and endosperm development at an early stage after pollination.Utilizing 21 polymorphic SSR markers,the mn2-m1 locus was limited to a 209.9-kb interval using 9176 recessive individuals of a BC1 segregating population from mn2-m1/B73.Only one annotated gene was located in this 209.9 kb region,Zm00001 d019294,which was predicted to encode nitrate transporter1.5(NRT1.5).Allelism tests confirmed that mn2-m1 was allelic to miniature2-m2(mn2-m2)and miniature2-710 B(mn2-710 B).The mn2-m1 and mn2-m2 alleles both had nucleotide deletions in the coding region resulting in premature termination,and the mn2-710 B allele had some missence mutations.Subcellular localization showed that Miniature 2(MN2)is localized in the plasma membrane.Quantitative real-time PCR(qRT-PCR)analysis revealed that the expression of MN2 and some genes involved in the basal endosperm transfer layer(BETL)and embryo surrounding region(ESR)development were affected in mn2-m1 seeds.These results suggested that MN2 plays an important role in maize seed development.

Functional assessment of cadherin as a shared mechanism for cross/dual resistance to Cry1Ac and Cry2Ab in Helicoverpa zea

Helicoverpa zea is a major target pest of pyramided transgenic crops expressing Cry1,Cry2 and/or Vip3Aa proteins from Bacillus thuringiensis(Bt)in the United States.Laboratory-selected Cry1Ac/Cry2Ab cross resistance and fieldevolved practical dual resistance of H.zea to these two toxins have been widely reported.Whether the widespread Cry1Ac/Cy2Ab dual resistance of H.zea has resulted from the selection of one shared or two independent resistance mechanisms by pyramided Bt crops remains unclear.Cadherin is a well-confirmed receptor of Cry1Ac and a suggested receptor of Cry2Ab in at least three Lepidopteran species.To test whether cadherin may serve as one shared mechanism for the cross and dual resistance of H.zea to Cry1Ac and Cry2Ab,we cloned H.zea cadherin(HzCadherin)cDNA and studied its functional roles in the mode of action of Cry1Ac and Cry2Ab by gain-and lossof-function analyses.Heterologous expression of HzCadherin in H.zea midgut,H.zea fat body and Sf9 cells made all three of these cell lines more susceptible to activated Cry1Ac but not activated Cry2Ab,whereas silencing HzCadherin of H.zea midgut and fat body cells significantly reduced the susceptibility to Cry1Ac but not Cry2Ab.Likewise,suppressing HzCadherin with siRNA made H.zea larvae resistant to Cry1Ac.These results clearly demonstrate that HzCadherin is not a receptor for Cry2Ab,and thus it is unlikely to serve as one shared mechanism for the cross and dual resistance of H.zea to Cry1Ac and Cry2Ab.

ZmCYP90D1 regulates maize internode development by modulating brassinosteroid-mediated cell division and growth

Plant height(PH)is associated with lodging resistance and planting density,which is regulated by a complicated gene network.In this study,we identified a spontaneous dwarfing mutation in maize,m30,with decreased internode number and length but increased internode diameter.A candidate gene,ZmCYP90D1,which encodes a member of the cytochrome P450 family,was isolated by map-based cloning.ZmCYP90D1 was constitutively expressed and showed highest expression in basal internodes,and its protein was targeted to the nucleus.A G-to-A substitution was identified to be the causal mutation,which resulted in a truncated protein in m30.Loss of function of ZmCYP90D1 changed expression of hormoneresponsive genes,in particular brassinosteroid(BR)-responsive genes which is mainly involved in cell cycle regulation and cell wall extension and modification in plants.The concentration of typhasterol(TY),a downstream intermediate of ZmCYP90D1 in the BR pathway,was reduced.A haplotype conferring dwarfing without reducing yield was identified.ZmCYP90D1 was inferred to influence plant height and stalk diameter via hormone-mediated cell division and cell growth via the BR pathway.

Accumulation of glycolipids in wheat grain and their role in hardness during grain development

Grain hardness is an important parameter for wheat quality. To understand the role of glycolipids in the formation of grain hardness, the glycolipid contents in wholegrain wheat flour and the starch granule surfaces of oven-dried and freeze-dried hard and soft wheat grain were analyzed. Changes in endosperm structure and amyloplast membrane integrity during grain development were also examined by electron microscopy. The monogalactosyldigylcerol(MGDG) and digalactosyldigylcerol(DGDG) contents of the starch surface were significantly higher in soft wheat than in hard wheat, regardless of the drying method or developmental stage. Throughout grain development, MGDG content was significantly higher in the starch surface of freeze-dried hard wheat than in the starch surface of oven-dried hard wheat. In contrast, the MGDG content of the starch surface was significantly higher in freeze-dried soft grain at 14 and 35 days after anthesis. No significant difference was observed in puroindoline protein(PIN) accumulation in wholegrain flour from wheat that was dried using the two methods, whereas PIN accumulation on the starch surface of freeze-dried grain was lower than that on the starch surface of oven-dried grain.The gap between the amyloplast membrane and starch granules was larger in hard wheat than in soft wheat, as shown by transmission electron microscopy. For the same wheat cultivar, this gap was larger for oven-dried than for freeze-dried grain. The content of polar lipids in the starch surface was closely related to grain hardness, and the breakdown of the amyloplast membrane may determine the location of polar lipids on the starch surface.

Physiological mechanisms underlying reduced photosynthesis in wheat leaves grown in the field under conditions of nitrogen and water deficiency

Reduced photosynthesis results directly from nitrogen or water deficiency in wheat plants,and leads to a decrease in grain yield.In this study,by measuring the effects of water and N deficiencies,both individually and combined,we characterized the responses of wheat(Triticum aestivum L.Yumai 49-198)plants to these two deficiencies using physiological measurements and comparative proteomics.Significant decreases in grain yield and leaf photosynthetic performance were observed in all deficiency conditions,and 106 photosynthetic proteins that showed responses were identified.Nitrogen deficiency induced the least change in photosynthetic proteins,and similar changes in most of these proteins were also observed for the combined nitrogen and water deficiencies.Water deficiency induced the largest change in photosynthetic proteins and resulted in the lowest 1000-kernel weight.Severe decreases in photosynthesis in both the water-deficiency and combined N and water deficiency groups were reflected mainly in an imbalanced ATP/NADPH ratio associated with the light reaction,which influences carbon metabolism in the Calvin cycle.Photorespiration was respectively stimulated or inhibited by N or water deficiency,while suppression of photorespiratory flux and activation of nitrogen recycling were observed in the combined N and water deficiency treatments.Comparison of photosynthetic proteins between experimental sites suggested that precipitation affected linear electron flow in the photoreaction,and thus photosynthetic efficiency.Our results provide a baseline for future studies of the roles of these photosynthetic proteins in the response to N or water deficiency and their effect on 1000-kernel weight.

Heredity and gene mapping of a novel white stripe leaf mutant in wheat

Spotted leaf(spl)mutant is a type of leaf lesion mimic mutants in plants.We obtained some lesion mimic mutants from ethyl methane sulfonate(EMS)-mutagenized wheat(Triticum aestivum L.)cultivar Guomai 301(wild type,WT),and one of them was named as white stripe leaf(wsl)mutant because of the white stripes on its leaves.Here we report the heredity and gene mapping of this novel wheat mutant wsl.There are many small scattered white stripes on the leaves of wsl throughout its whole growth period.As the plants grew,the white stripes became more severe and the necrotic area expanded.The mutant wsl grew only weakly before the jointing stage and gradually recovered after jointing.The length and width of the flag leaf,spike number per plant and thousand-grain weight of wsl were significantly lower than those of the WT.Genetic analysis indicated that the trait of white stripe leaf was controlled by a recessive gene locus,named as wsl,which was mapped on the short arm of chromosome 6 B by SSR marker assay.Four SSR markers in the F2 population of wsl×CS were linked to wsl in the order of Xgpw1079–Xwmc104–Xgwm508-wsl–Xgpw7651 at 7.1,5.2,8.7,and 4.4 c M,respectively and three SSR markers in the F2 population of wsl×Jimai 22 were linked to wsl in the order of Xgwm508–Xwmc494–Xgwm518-wsl at 3.5,1.6 and 8.2 c M,respectively.In comparison to the reference genome sequence of Chinese Spring(CS),wsl is located in a 91-Mb region from 88 Mb(Xgwm518)to 179 Mb(Xgpw7651)on chromosome 6 BS.Mutant wsl is a novel germplasm for studying the molecular mechanism of wheat leaf development.

Identification of herbicide resistance loci using a genome-wide association study and linkage mapping in Chinese common wheat

Carfentrazone-ethyl and tribenuron-methyl,the two widely used herbicides for weed control in field crops,frequently cause phytotoxicity to wheat seedlings in the field.In this study,a total of 697 wheat accessions containing three panels were scanned using wheat90 K and 660 K SNP arrays to identify important herbicide resistance loci.Genome-wide association study(GWAS)revealed 329 significant single-nucleotide polymorphisms(SNPs)with phenotypic variance explained(PVE)of 11.3%to 27.6%.Among these SNPs,15 were detected in multiple environments and they were mainly distributed on chromosomes 1 B,2 D,5 B,5 D,6 D,and 7 D.Further analysis indicated that g HR-5 B(467–587 Mb),g HR-7 D(46–52 Mb),and g HR-1 B(517–580 Mb)were important herbicide resistance loci in wheat.Linkage mapping in a bi-parental population detected one QTL(q HR-1 B)with PVE of 7.44%to8.28%.This is reliable locus because its physical position(554–566 Mb)overlapped with g HR-1 B by GWAS in the genome of Chinese Spring.This study provided some herbicide-resistant germplasm and important genetic loci for identifying genes of common wheat.

Identification of the candidate gene controlling tiller angle in common wheat through genome-wide association study and linkage analysis

Wheat tiller angle(TA)is an important agronomic trait that contributes to grain production by affecting plant architecture.It also plays a crucial role in high-yield wheat breeding.An association panel and a recombinant inbred line(RIL)population were used to map quantitative trait loci(QTL)for TA.Results showed that 470 significant SNPs with 10.4%–28.8%phenotypic variance explained(PVE)were detected in four replicates by a genome-wide association study(GWAS).Haplotype analysis showed that the TA_Hap_4B1 locus on chromosome 4B was a major QTL to regulate wheat TA.Ten QTL were totally detected by linkage mapping with the RIL population,and QTA.hau-4B.1 identified in six environments with the PVE of 7.88%–18.82%was a major and stable QTL.A combined analysis demonstrated that both TA_Hap_4B1 and QTA.hau-4B.1 were co-located on the same region.Moreover,QTA.hau-4B.1 was confirmed by bulked segregant RNA-Seq(BSR-Seq)analysis.Phenotypic analysis showed that QTA.hau-4B.1was also closely related to yield traits.Furthermore,Traes CS4B02G049700 was considered as a candidate gene through analysis of gene sequence and expression.This study can be potentially used in cloning key genes modulating wheat tillering and provides valuable genetic resources for improvement of wheat plant architecture.

Characterization of Ppd-D1 alleles on the developmental traits and rhythmic expression of photoperiod genes in common wheat

Photoperiodic response is an important characteristic that plays an important role in plant adaptability for various environments. Wheat cultivars grow widely and have high yield potential for the strong photoperiod adaptibility. To assess the photoperiodic response of different genotypes in wheat cultivars, the photoperiodic effects of the Ppd-D1 alleles and the expressions of the related TaGI, TaCO and Ta FT genes in Liaochun 10 and Ningchun 36 were investigated under the short-day（6 h light, SD）, moderate-day（12 h light, MD） and long-day（24 h light, LD） conditions. Amplicon length comparison indicated that the promoter of Ppd-D1 in Ningchun 36 is intact, while Liaochun 10 presented the partial sequence deletion of Ppd-D1 promoter. The durations of all developmental stages of the two cultivars were reduced by subjection to an extended photoperiod, except for the stamen and pistil differentiation stage in the Liaochun 10 cultivar. The expression levels of the Ppd-D1 alleles and the TaGI, TaCO and TaFT genes associated with the photoperiod pathway were examined over a 24-h period under SD and MD conditions. The relationships of different photoperiodic responses of the two cultivars and the expression of photoperiod pathway genes were analyzed accordingly. The photoperiod insensitive（PI） genotype plants flower early under SD; meanwhile, the abnormal expression of the Ppd-D1 a allele is accompanied with an increase in Ta FT1 expression and the TaCO expression variation. The results would facilitate molecular breeding in wheat.

Systematic dissection of disease resistance to southern corn rust by bulked-segregant and transcriptome analysis

Southern corn rust(SCR) is a destructive maize disease caused by Puccinia polysora Underw. To investigate the mechanism of SCR resistance in maize, a highly resistant inbred line, L119 A, and a highly susceptible line, Lx9801, were subjected to gene mapping and transcriptome analysis. Bulked-segregant analysis coupled with whole-genome sequencing revealed several quantitative trait loci(QTL) on chromosomes 1, 6, 8, and 10. A set of 25 genes, including two coiled-coil nucleotide-binding site leucine-rich repeat(CC-NBS-LRR) genes, were identified as candidate genes for a major-effect QTL on chromosome 10. To investigate the mechanism of SCR resistance in L119 A, RNA-seq of P. polysorainoculated and non-inoculated plants of L119 A and Lx9801 was performed. Unexpectedly, the number of differentially expressed genes in inoculated versus non-inoculated L119 A plants was about 10 times that of Lx9801, with only 29 common genes identified in both lines, suggesting extensive gene expression changes in the highly resistant but not in the susceptible line. Based on the transcriptome analysis, one of the CC-NBS-LRR candidate genes was confirmed to be upregulated in L119 A relative to Lx9801 independently of P. polysora inoculation. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses indicated that transcription factors, as well as genes involved in defense responses and metabolic processes, were dominantly enriched, with the phenylpropanoid biosynthesis pathway most specifically activated. Consistently, accumulation of phenylpropanoid-derived lignin, especially S lignin, was drastically increased in L119 A after P. polysora inoculation, but remained unchanged in Lx9801, suggesting a critical role of lignin in SCR resistance. A regulatory network of defense activation and metabolic change in SCR-resistant maize upon P. polysora infection is described.