Identification of Fusarium wilt resistance gene SiRLK1 in Sesamum indicum L.

Sesame Fusarium wilt(SFW),caused by Fusarium oxysporum f.sp.sesami(Fos),is one of the most devastating diseases affecting sesame cultivation.Deciphering the genetic control of SFW resistance is pivotal for effective disease management in sesame.An inheritance study on a cross between the highly resistant variety Yuzhi 11 and the highly susceptible accession Sp1 using a Fos pathogenicity group 1 isolate indicated that resistance was conferred by a single dominant allele.The target locus was located in a 1.24 Mb interval on chromosome 3 using a combination of cross-population association mapping and bulked segregant analysis.Fine genetic mapping further narrowed the interval between 21,350 and 21,401 kb.The locus Sindi_0812400 was identified as the SFW resistance gene and officially designated SiRLK1.This gene encodes a specific malectin/receptor-like protein kinase with three putative tandem kinase domains and is considered a kinase fusion protein.Sequence analysis revealed that a high proportion(49.44%)of variants within the locus was located within the kinase domainⅢ,and several of which were evidently associated with the diversity in SFW response,indicating the critical role of kinase domainⅢin expression of disease resistance.These findings provide valuable information for further functional analysis of SFW resistance genes and marker-assisted resistance breeding in sesame.

Physiological and Transcriptome Analysis Illuminates the Molecular Mechanisms of the Drought Resistance Improved by Alginate Oligosaccharides in Triticum aestivum L.

Alginate oligosaccharides(AOS)enhance drought resistance in wheat(Triticum aestivum L.),but the definite mechanisms remain largely unknown.The physiological and transcriptome responses of wheat seedlings treated with AOS were analyzed under drought stress simulated with polyethylene glycol-6000.The results showed that AOS promoted the growth of wheat seedlings and reduced oxidative damage by improving peroxidase and superoxide dismutase activities under drought stress.A total of 10,064 and 15,208 differentially expressed unigenes(DEGs)obtained from the AOS treatment and control samples at 24 and 72 h after dehydration,respectively,were mainly enriched in the biosynthesis of secondary metabolites(phenylpropanoid biosynthesis,flavonoid biosynthesis),carbohydrate metabolism(starch and sucrose metabolism,carbon fixation in photosynthetic organisms),lipid metabolism(fatty acid elongation,biosynthesis of unsaturated fatty acids,alpha-linolenic acid metabolism,cutin,suberine and wax biosynthesis),and signaling transduction pathways.The up-regulated genes were related to,for example,chlorophyll a-b binding protein,amylosynthease,phosphotransferase,peroxidase,phenylalanine ammonia lyase,flavone synthase,glutathione synthetase.Signaling molecules(including MAPK,plant hormones,H_(2)O_(2) and calcium)and transcription factors(mainly including NAC,MYB,MYB-related,WRKY,bZIP family members)were involved in the AOS-induced wheat drought resistance.The results obtained in this study help underpin the mechanisms of wheat drought resistance improved by AOS,and provides a theoretical basis for the application of AOS as an environmentally sustainable biological method to improve drought resistance in agriculture.

Irrigation and nitrogen fertiliser optimisation in protected vegetable fields of northern China:Achieving environmental and agronomic sustainability

Globally,sub-optimal use of nitrogen (N) fertiliser and elevated N irrigation groundwater have led to high leached nitrate (NO_(3)^(–)) losses from protected vegetable field systems.Optimising fertiliser and irrigation management in different soil types is crucial to reduce future N loads from such systems.The present 4-year study examined leached N loads from lysimeter monitoring arrays set up across 18 protected vegetable system sites encompassing the dominant soil types of northern China.The treatments applied at each field site were:1) a high N and high irrigation input treatment (HNHI);2) a low N but high irrigation input treatment (LNHI) and 3) a low N with low irrigation input treatment (LNLI).Results showed that the mean annual leached total nitrogen loads from the HNHI,LNHI and LNLI treatments were 325,294 and 257 kg N ha^(–1) in the fluvo-aquic soil,114,100 and 78 kg N ha^(–1) in the cinnamon soil and 79,68 and 57 kg N ha^(–1) in the black soil,respectively.The N dissolved in irrigation water in the fluvo-aquic soil areas was 8.26-fold higher than in the cinnamon areas.A structural equation model showed that N fertiliser inputs and leaching water amounts explained 14.7 and 81.8%of the variation of leached N loads,respectively.Correspondingly,reducing irrigation water by 21.5%decreased leached N loads by 20.9%,while reducing manure N and chemical N inputs by 22 and 25%decreased leached N loads by only 9.5%. This study highlights that protected vegetable fields dominated by fluvo-aquic soil need management to curtail leached N losses in northern China.

A study of the soil water potential threshold values to trigger irrigation of ‘Shimizu Hakuto’ peach at pivotal fruit developmental stages

Water management is an important practice that affects fruit size and quality.Effective implementation of irrigation scheduling requires knowledge of the appropriate indicators and thresholds,which are established manly based on the effects of water deficits on final fruit quality.Few studies have focused on the real-time effects of water status on fruit and shoot growth.To establish soil water potential (ψ_(soil)) thresholds to trigger irrigation of peach at pivotal fruit developmental stages,photogrammetry,^(13)C labelling,and other techniques were used in this study to investigate real-time changes in stem diameter,fruit projected area,net leaf photosynthetic rate (P_(n)),and allocation of photoassimilates to fruit under soil water potential conditions ranging from saturation to stress in 6-year-old Shimizu hakuto’peach.Stem growth,fruit growth,and P_n exhibited gradually decreasing sensitivity to water deficits during fruit developmental stages I,II,and III.Stem diameter growth was significantly inhibited whenψ_(soil)dropped to-8.5,-7.6,and-5.4 k Pa,respectively.Fruit growth rate was low,reaching zero when theψ_(soil)was-9.0 to-23.1,-14.9 to-21.4,and-16.5 to-23.3 k Pa,respectively,and P_ndecreased significantly when theψ_(soil)reached-24.2,-22.7,and-20.4 kPa,respectively.In addition,more photoassimilates were allocated to fruit under moderateψ_(soil)conditions (-10.1 to-17.0 k Pa) than under otherψ_(soil)values.Our results revealed threeψ_(soil)thresholds,-10.0,-15.0,and-15.0 kPa,suitable for triggering irrigation during stages I,II,and III,respectively.These thresholds can be helpful for controlling excessive tree vigor,maintaining rapid fruit growth and leaf photosynthesis,and promoting the allocation of more photoassimilates to fruit.

Fine-mapping of a candidate gene for web blotch resistance in Arachis hypogaea L.

Peanut(Arachis hypogaea L.)is a globally important oil crop.Web blotch is one of the most important foliar diseases affecting peanut,which results in serious yield losses worldwide.Breeding web blotch-resistant peanut varieties is the most effective and economically viable method for minimizing yield losses due to web blotch.In the current study,a bulked segregant analysis with next-generation sequencing was used to analyze an F2:3 segregating population and identify candidate loci related to web blotch resistance.Based on the fine-mapping of the candidate genomic interval using kompetitive allele-specific PCR(KASP)markers,we identified a novel web blotch resistance-related locus spanning approximately 169 kb on chromosome 16.This region included four annotated genes,of which only Arahy.35VVQ3 had a non-synonymous single nucleotide polymorphism in the coding region between the two parents.Two markers(Chr.16.12872635 and Chr.16.12966357)linked to this gene were shown to be co-segregated with the resistance of peanut web blotch by 72 randomly selected recombinant inbred lines(RIL),which could be used in marker-assisted breeding of resistant peanut varieties.

Effects of Seeding Date and Density on Yield and Agronomic Traits of Millet : A Case Study of Wangu 098 Variety of Millet

[Objectives]To find out a suitable cultivation technique of Wangu 098 in Nanyang area,speed up the popularization,demonstration and application of Wangu 098,and provide a theoretical and practical basis for adjusting the planting structure and realizing the matching of improved varieties and methods.[Methods]The new self-bred millet variety Wangu 098 was used as the material,and the two-factor split zone experimental design was adopted.The effects of different sowing dates and densities on the yield,growth period and agronomic characters of millet were studied.[Results]The interaction of seeding date and density had a great effect on the yield and plant traits of millet.Millet yield was significantly and positively correlated with plant height,panicle length,single panicle weight,panicle grain weight and tiller number.[Conclusions]The reasonable combination of seeding date and density could give full play to the yield potential of millet.According to the experimental results and cultivation experience,the suitable seeding date of millet in Nanyang area is in the first and middle ten days of June,and the best density is about 750000 plants/ha.However,after June 30,the seeding millet did not tiller,so the density should be increased to more than 900000 plants/ha to obtain higher yield.In terms of cultivation and management,timely seeding,reasonable close planting,and coordination of vegetative growth and reproductive growth can make the plant tall and strong,panicle long and thick,and improve the yield of millet.

Threshold of Soil pH for Occurrence of Tobacco Bacterial Wilt in Henan Province

[Objective]The paper was to study the relationship between spatial distribution characteristics of soil p H and bacterial wilt in tobacco-growing area in Henan Province.[Method]The 21 tobacco-growing fields infected by bacterial wilt and 91 tobacco-growing fields with no cases were selected from Henan Province,and the pH of fields was determined.[Result]Bacterial wilt mainly occurred in the tobacco-growing fields in Luoshan,Pingqiao,Queshan,Biyang,Suiping,and Xiping,and the soil pH mainly ranged from 5.5 to 6.5(accounted for 84.75%of total surveyed tobacco fields);bacterial wilt had not been found in tobacco-growing fields in Tanghe,Zhengyang,Shangcai,Sheqi,Wuyang and Chenqu,and the soil pH mainly ranged from 6.5 to 7.0(accounted for 81.25%of total surveyed tobacco fields).There were significant differences in soil pH between the fields with and without bacterial wilt,and soil pH 6.5 could be regarded as the threshold for the occurrence of tobacco bacterial wilt in Henan Province.There was extremely significantly positive linear correlation between soil p H and latitude(y=0.7375 x-17.799,R2=0.386,P<0.01).The geographical boundary of soil pH 6.5 was roughly 33°N,and bacterial wilt was less likely to occur in the north tobacco-growing areas of the boundary.[Conclusion]The study will provide a scientific basis for the prevention and control of tobacco bacterial wilt in Henan.

Identification of a pleiotropic QTL cluster for Fusarium head blight resistance,spikelet compactness,grain number per spike and thousand-grain weight in common wheat

Simultaneously improving Fusarium head blight(FHB)resistance and grain yield is challenging in wheat breeding.The correlations between spikelet compactness(SC),grain number per spike(GNS),thousandgrain weight(TGW)and FHB resistance remains unclear in common wheat.Identification of major quantitative trait loci(QTL)conferring FHB resistance and yield components,and development of breeder-friendly markers for the QTL are prerequisites for marker-assisted selection(MAS).Here,a recombinant inbred line(RIL)population derived from a cross between a resistant cultivar Yangmai 12(YM12)and a susceptible cultivar Yanzhan 1(YZ1)was used to map QTL for FHB resistance and yield components.A total of 22 QTL were identified;among these,six are likely to be new for corresponding traits.A QTL cluster(Qclu.yas-2D)for FHB type II resistance,SC,GNS,and TGW was detected on chromosome 2D.Breeder-friendly kompetitive allele-specific PCR(KASP)markers flanking the interval of Qclu.yas-2D were developed and validated in a diverse panel of 166 wheat cultivars and advanced lines.The YM12 alleles of Qclu.yas-2D significantly increased FHB resistance,SC,and GNS but decreased TGW in the validation population.The KASP markers developed for Qclu.yas-2D have great potential for breeding high-yielding wheat cultivars with enhanced FHB resistance.

Diversity and association analysis of important agricultural trait based on miniature inverted-repeat transposable element specific marker in Brassica napus L.

Miniature inverted-repeat transposable elements(MITEs)are a group of DNA transposable element(TE)which preferentially distributed with gene associated regions.Tens of MITEs families have been revealed in Brassica napus genome,they scatter across the genome with tens of thousands copies and produce polymorphisms both intra-and inter-species.Our previous studies revealed a Tourist-like MITE,Monkey King,associated with vernalization requirement of B.napus,however there are still few studies reveal MITE association with agricultural traits in B.napus.In the present study,80 polymorphic markers were developed from 55 MITEs,and used to evaluate genetic diversity in a panel of B.napus accessions consisting of 101 natural and 25 synthetic genotypes.Five agricultural traits,oil content,glucosinolate content,erucic acid content,weight of thousand seeds(WTS)and plant height,were investigated across 3-years field experiments,in addition,two traits,hypocotyl length and root length,were evaluated at the 4-leaf stage in the laboratory.Correlations between the MITE-based markers and seven traits were analyzed,finally,10 polymorphic markers produced by 6 pairs of MITE specific primers were revealed relatively high correlation with 5 traits.Two polymorphic markers were anchored with two candidate genes,BnaA02g13530D and BnaA08g20010D,respectively,which may contribute to glucosinolate content and WTS.This research may contribute to genetic improvement through utilization of MITE-induced polymorphisms in Brassica species.

Current Situation of Table Grape Industry in Henan Province and Development Recommendations

Through the investigation of the current production situation,regional distribution,variety structure,production organization and existing problems of table grapes in Henan Province,this paper conducted an in-depth analysis on the advantages and disadvantages of the development of table grapes industry in Henan Province.In view of the current problems and development trend,it came up with some pertinent recommendations,including transforming the concept of cultivation,adhering to the principle of"high-quality varieties,standardized cultivation,mechanized management,large-scale operation,and diversified market",strengthening brand building,and promote the integrated development of the primary,secondary and tertiary industries,so as to promote the change of table grape industry in Henan Province from"quantitative scale model"to"quality benefit model",and promote its sustainable and high-quality development.

Comprehensive analysis of the full-length transcripts and alternative splicing involved in clubroot resistance in Chinese cabbage

Chinese cabbage is an economically important Brassica vegetable worldwide, and clubroot, which is caused by the soilborne protist plant pathogen Plasmodiophora brassicae is regarded as a destructive disease to Brassica crops. Previous studies on the gene transcripts related to Chinese cabbage resistance to clubroot mainly employed RNA-seq technology,although it cannot provide accurate transcript assembly and structural information. In this study, PacBio RS II SMRT sequencing was used to generate full-length transcriptomes of mixed roots at 0, 2, 5, 8, 13, and 22 days after P. brassicae infection in the clubroot-resistant line DH40R. Overall, 39 376 high-quality isoforms and 26 270 open reading frames(ORFs) were identified from the SMRT sequencing data. Additionally, 426 annotated long noncoding RNAs(lncRNAs),56 transcription factor(TF) families, 1 883 genes with poly(A) sites and 1 691 alternative splicing(AS) events were identified. Furthermore, 1 201 of the genes had at least one AS event in DH40R. A comparison with RNA-seq data revealed six differentially expressed AS genes(one for disease resistance and five for defensive response) that are potentially involved in P. brassicae resistance. The results of this study provide valuable resources for basic research on clubroot resistance in Chinese cabbage.

Development of Oligo-GISH kits for efficient detection of chromosomal variants in peanut

Oligo probe staining is a low-cost and efficient chromosome identification technique.In this study,oligo genomic in situ hybridization(Oligo-GISH)technology was established in peanut.Peanut A and B subgenome-specific interspersed repeat(IR)oligo probe sets were developed based on clustering and electronic localization of tandem repeat sequences in the reference genome of Tifrunner.The OligoGISH kit was then used to perform staining of 15 Arachis species.The A-subgenome probe set stained the chromosomes of A-and E-genome Arachis species,the B-subgenome probe set stained those of B-,F-,K-,and E-genome species,and neither set stained those of H-genome species.These results indicate the relationships among the genomes of these Arachis species.The Oligo-GISH kit was also used for batch staining of the chromosomes of 389 seedlings from the irradiated M1generation,allowing 67 translocation and deletion lines to be identified.Subsequent Oligo-FISH karyotyping,FISH using single-copy probe libraries,and trait investigation identified seven homozygous chromosomal variants from the M3generation and suggested that there may be genes on chromosome 4B controlling seed number per pod.These findings demonstrate that the IR probe sets and method developed in this study can facilitate research on distant hybridization and genetic improvement in peanut.

Are the two polymorphic sites of anti-Marek’s disease in White Leghorn chickens also suitable for Partridge Shank chickens?

Background:The selection of Marek’s disease(MD)-resistant breeds in Partridge Shank chicken,a popular local chicken breed in Henan Province of China,has practical value.We hypothesized that the two polymorphic sites(rs14527240 located in SMOC1 and GGaluGA156129 located in PTPN3)related to MD resistance in White Leghorn chickens are also applicable to Partridge Shank chickens.Methods:In this experiment,we screened 10 live hens and 2 live roosters with the double GG genotype by genotyping the two sites from 6500 Partridge Shank chickens.Nineteen one-day-old chicks with the double GG genotype were obtained by artificial insemination.Seventy-two one-day-old chickens(19 from the population expansion test and 53 randomly selected from chicken farms)were injected with 2000 plaque-forming units of the Md5 virus strain.After 100 days of infection,all chickens were examined by pathological anatomical examination,histological sectioning,genotyping,and a quantitative polymerase chain reaction of SMOC1 and PTPN3.Results:There was only one site(rs14527240 located in SMOC1)associated with MD in Partridge Shank chickens(p<0.05),but the GG genotype of SMOC1 in Partridge Shank chickens indicated susceptibility to MD.SMOC1 expression in MD-susceptible chickens was also significantly higher than that in MDresistant chickens(p<0.05).Conclusion:Therefore,the MD resistance sites selected from White Leghorn chickens were not completely suitable for Partridge Shank chickens,but they can be used as a reference.This study indicated that SMOC1 plays an important role in screening for MD resistance in poultry.

The combination of DNA methylation and positive regulation of anthocyanin biosynthesis by MYB and bHLH transcription factors contributes to the petal blotch formation in Xibei tree peony

Xibei tree peony is a distinctive cultivar group that features red–purple blotches in petals.Interestingly,the pigmentations of blotches and non-blotches are largely independent of one another.The underlying molecular mechanism had attracted lots of attention from investigators,but was still uncertain.Our present work demonstrates the factors that are closely related to blotch formation in Paeonia rockii‘Shu Sheng Peng Mo’.Non-blotch pigmentation is prevented by the silencing of anthocyanin structural genes,among which PrF3H,PrDFR,and PrANS are the three major genes.We characterized two R2R3-MYBs as the key transcription factors that control the early and late anthocyanin biosynthetic pathways.PrMYBa1,which belongs to MYB subgroup 7(SG7)was found to activate the early biosynthetic gene(EBG)PrF3H by interacting with SG5 member PrMYBa2 to form an‘MM’complex.The SG6 member PrMYBa3 interacts with two SG5(IIIf)bHLHs to synergistically activate the late biosynthetic genes(LBGs)PrDFR and PrANS,which is essential for anthocyanin accumulation in petal blotches.The comparison of methylation levels of the PrANS and PrF3H promoters between blotch and non-blotch indicated a correlation between hypermethylation and gene silencing.The methylation dynamics of PrANS promoter during flower development revealed a potential early demethylating reaction,which may have contributed to the particular expression of PrANS solely in the blotch area.We suggest that the formation of petal blotch may be highly associated with the cooperation of transcriptional activation and DNA methylation of structural gene promoters.

Production profile and comparison analysis of main toxin components of Fusarium oxysporum f.sp.sesami isolates with different pathogenicity levels

Fusarium wilt is a common fungal disease in sesame caused by Fusarium oxysporum f.sp.sesami(FOS).To determine the toxin production profiles of the FOS isolates with different pathogenicity levels under various culture conditions,we assessed the content variation of fusaric acid(FA)and 9,10-dehydrofusaric acid(9,10-DFA)produced by the four representative FOS isolates.Results indicated that the concentration of FA reached to a maximum of 2848.66μg/mL in Czapek medium,while 9,10-DFA was mainly produced in Richard and Lowcarbon Richard medium.The concentration of 9,10-DFA on Richard culture medium varied from 0μg/mL to 716.89μg/mL.Of the five culture media used in this study,Czapek culture medium was the most conductive to produce FA.FA production was significantly affected by culture medium,culture time,and their interactions.Results suggest that there is no correlation between toxin production and pathogenicity level of FOS isolates.These findings provide key information for the mechanism analysis of FOS-sesame interaction and pathogen control.

The prevalence of deleterious mutations during the domestication and improvement of soybean

Soybean(Glycine max L.)is a protein and oil crop grown worldwide.Its fitness may be reduced by deleterious mutations,whose identification and purging is desirable for crop breeding.In the published whole-genome re-sequenced data of 2214 soybean accessions,including 221 wild soybean,1132 landrace cultivars and 861 improved soybean lines,we identified 115,275 deleterious single-nucleotide polymorphisms(SNPs).Numbers of deleterious alleles increased from wild soybeans to landraces and decreased from landraces to modern improved lines.Genes in selective-sweep regions showed fewer deleterious mutations than the remaining genes.Deleterious mutations explained 4.3%-48%more phenotypic variation than randomly selected SNPs for resistance to soybean cyst nematode race 2(SCN2),soybean cyst nematode race 3(SCN3)and soybean mosaic virus race 3(SMV3).These findings illustrate how mutation load has shifted during soybean domestication,expansion and improvement and provide candidate sites for breeding out deleterious mutations in soybean by genome editing and/or conventional breeding focused on the selection of progeny with fewer deleterious alleles.

Soybean(Glycine max)rhizosphere organic phosphorus recycling relies on acid phosphatase activity and specific phosphorusmineralizing-related bacteria in phosphate deficient acidic soils

Bacteria play critical roles in regulating soil phosphorus(P) cycling. The effects of interactions between crops and soil P-availability on bacterial communities and the feedback regulation of soil P cycling by the bacterial community modifications are poorly understood. Here, six soybean(Glycine max) genotypes with differences in P efficiency were cultivated in acidic soils with long-term sufficient or deficient P-fertilizer treatments. The acid phosphatase(AcP) activities, organic-P concentrations and associated bacterial community compositions were determined in bulk and rhizosphere soils. The results showed that both soybean plant P content and the soil AcP activity were negatively correlated with soil organic-P concentration in P-deficient acidic soils. Soil P-availability affected the ɑ-diversity of bacteria in both bulk and rhizosphere soils. However, soybean had a stronger effect on the bacterial community composition, as reflected by the similar biomarker bacteria in the rhizosphere soils in both P-treatments. The relative abundance of biomarker bacteria Proteobacteria was strongly correlated with soil organic-P concentration and AcP activity in low-P treatments. Further high-throughput sequencing of the phoC gene revealed an obvious shift in Proteobacteria groups between bulk soils and rhizosphere soils, which was emphasized by the higher relative abundances of Cupriavidus and Klebsiella, and lower relative abundance of Xanthomonas in rhizosphere soils. Among them, Cupriavidus was the dominant phoC bacterial genus, and it was negatively correlated with the soil organic-P concentration. These findings suggest that soybean growth relies on organic-P mineralization in P-deficient acidic soils, which might be partially achieved by recruiting specific phoCharboring bacteria, such as Cupriavidus.

Effects of Water-Collecting and -Retaining Techniques on Photosynthetic Rates, Yield, and Water Use Efficiency of Millet Grown in a Semiarid Region

Field experiments were conducted in 2003 and 2004 to study the effects of plastic ridges and furrow film mulching （plastic film on sowing, as well as plastic film on flat soil and hole sowing） and chemicals （a drought resistant agent and a water- retaining agent） on growth, photosynthetic rate, yield, and water use efficiency （WUE） of spring millet （Setaria italica L.）. The experimental results showed that water-collecting and -retaining techniques can effectively increase soil moisture content, the leaf photosynthetic rate and crop growth. Due to increased soil moisture under the plastic-covered ridge and furrow water-collecting in July and August, dry matter and plant height had a increase at the booting stage （late growth advantage）. However, the plastic-covered flat soil and hole sowing reduced soil evaporation during early growth, the increase of dry matter and plant height appeared at the seedling stage （early growth advantage）. Plastic-covered ridge and furrow sowing supplemented with chemical reagents had significant positive effects on water collection and soil moisture retention. Improvement of soil moisture resulted into the increase of the photosynthetic rate, dry matter accumulation yield and WUE. The water-collecting and -retaining techniques can improve WUE and enhance crop yield. Correlation analysis demonstrated that the photosynthetic rate under the water-collecting and -retaining techniques was significantly associated with the soil moisture, but had no significant relationship with leaf chlorophyll content. Plastic- covered ridge and furrow sowing supplemented with chemical reagents increased the yield and WUE by 114% and 8.16 kg ha-1 mm-1, respectively, compared with the control; while without the chemical reagents the yield and WUE were 95% and 7.42 kg ha-1 mm-1 higher, respectively, than those of the control.

Identification of QTLs Related to Bolting in Brassica rapa ssp. pekinensis (syn. Brassica campestris ssp. pekinensis)

A genetic linkage map of Brassica rapa ssp. pekinensis was constructed with 186 AFLP （amplified fragment length polymorphism） markers by using a doubled-haploid （DH） population with 183 individuals. The individuals were derived from F1 which was developed by crossing a bolting resistant DH line Y-177-12 and an easy bolting DH line Y195-93a. AFLPs were generated by the use of restriction enzymes EcoR Ⅰ and Mse Ⅰ . The segregation of each marker and linkage was analyzed by using JoinMap version 3.0. Mapped markers were aligned in ten linkage groups which covered 887.8 cM with an average marker interval of 4.47 cM. Markers showing skewed segregation ratio were clustered in six LGs. Quantitative trait loci （QTL） were mapped for bolting resistance by using MAPQTL 4.0 package. Four QTLs explaining from 7.0 to 9.4% of the total variation were detected, all of them increase bolting resistance. These mapped QTLs could be used to develop a marker assisted selection programme for bolting resistance breeding.