Utilizing resequencing big data to facilitate Brassica vegetable breeding:tracing introgression pedigree and developing highly specific markers for clubroot resistance

Clubroot caused by Plasmodiophora brassicae is a devastating disease of Cruciferous crops.Developing cultivars with clubroot resistance(CR)is the most effective control measure.For the two major Brassica vegetable species B.rapa and B.oleracea,several commercial cultivars with unclear CR pedigrees have been intensively used as CR donors in breeding.However,the continuous occurrence of CR-breaking makes the CR pedigree underlying these cultivars one of the breeders'most urgent concerns.The complex intraspecific diversity of these two major Brassica vegetables has also limited the applicability of CR markers in different breeding programs.Here we first traced the pedigree underlying two kinds of CR that have been widely applied in breeding by linkage and introgression analyses based on public resequencing data.In B.rapa,a major locus CRzi8 underlying the CR of the commercial CR donor‘DegaoCR117’was identified.CRzi8 was further shown to have been introgressed from turnip(B.rapa ssp.rapifera)and that it carried a potential functional allele of Crr1a.The turnip introgression carried CRb^(c),sharing the same coding sequence with the CRb that was also identified from chromosome C07 of B.oleracea CR cultivars with different morphotypes.Within natural populations,variation analysis of linkage intervals of CRzi8,PbBa8.1,CRb,and CRb^(c)yielded easily resolved InDel markers(>20 bp)for these fundamental CR genes.The specificity of these markers was tested in diverse cultivars panels,and each exhibited high reliability in breeding.Our research demonstrates the value of the practice of applying resequencing big data to solve urgent concerns in breeding programs.

Fine mapping and cloning of the sterility gene Bra2Ms in nonheading Chinese cabbage(Brassica rapa ssp.chinensis)

The application of a male-sterile line is an ideal approach for hybrid seed production in non-heading Chinese cabbage(Brassica rapa ssp.chinensis).However,the molecular mechanisms underlying male sterility in B.rapa are still largely unclear.We previously obtained the natural male sterile line WS24-3 of non-heading Chinese cabbage and located the male sterile locus,Bra2Ms,on the A2 chromosome.Cytological observations revealed that the male sterility of WS24-3 resulted from disruption of the meiosis process during pollen formation.Fine mapping of Bra2Ms delimited the locus within a physical distance of about 129 kb on the A2 chromosome of B.rapa.The Bra039753 gene encodes a plant homeodomain(PHD)-finger protein and is considered a potential candidate gene for Bra2Ms.Bra039753 was significantly downregulated in sterile line WS24-3 compared to the fertile line at the meiotic anther stage.Sequence analysis of Bra039753 identified a 369 bp fragment insertion in the first exon in male sterile plants,which led to an amino acid insertion in the Bra039753 protein.In addition,the 369 bp fragment insertion was found to cosegregate with the male sterility trait.This study identified a novel locus related to male sterility in non-heading Chinese cabbage,and the molecular marker obtained in this study will be beneficial for the marker-assisted selection of excellent sterile lines in non-heading Chinese cabbage and other Brassica crops.

Variety Selection and Green Cultivation Technology of Courtyard Ornamental and Edible Peppers

In order to comply with the development trend of the multifunctional use of peppers,we conducted an investigation into the characteristics and features of varieties,potting management techniques,and the methods of extending the fruit ornamental period and other aspects of courtyard ornamental and edible peppers.A set of cultivation techniques suitable for courtyard ornamental and edible peppers has been developed,including timely sowing and seedling,nutrient soil preparation,water and fertilizer management,trimming and pruning,preservation of flowers and fruits,green prevention and control of diseases and pests,harvesting,and so on.

Safety Evaluation of Vegetables Growing in Soils Contaminated by Different Levels of Cadmium(Cd)

The tested soils containing different Cd levels were obtained by mixing the normal cultivated soils with the Cd-contaminated soils taken from the paddies near a mine. Five major categories of vegetables, i.e. cucumber, cowpea, Bok choy, radish and lettuce, widely planted in the spring and autumn in Hunan Province, were selected for pool-culture experiments. Results showed that the Cd accumulations varied greatly according to the category of vegetables. The Cd accumulations in cucumber and cowpea growing in soils with high Cd levels (1.5 mg/kg) were within the threshold limits of the national standards, meaning that these two categories are safe to grow in Cd-contaminated soils. For either the cucumber or the cowpea category, there were no significant differences in the Cd accumulations of different genotypes. Most of the tested Bok choy and radish cultivars could grow safely in soils whose Cd levels were below 1.0 mg/kg. In comparison, the Cd accumulations in some cultivars tended to increase sharply as the Cd level in the soil went beyond 1.0 mg/kg. Significant variations were also observed in the Cd accumulations of different genotypes with mounting Cd levels in the soil. Besides, there were no positive correlations between Cd accumulations in plants and Cd levels in soils, indicating large fluctuations and poor ecological stability of Bok choy and radish. Therefore, the planting of Bok choy and radish should be strictly evaluated and controlled in Cdcontaminated regions. The Cd contents of most celtuce cultivars growing in mildlycontaminated soils had already exceeded the threshold limit. Therefore, it is not safe for celtuce to grow in Cd-contaminated environments.

Study on Obstacles to Continuous Cropping of Vegetables and Soil Remediation Technology

Firstly,this paper analyzes the cause of obstacles to continuous cropping of vegetables,and then introduces the soil ecological remediation technology used for overcoming obstacles to continuous cropping of vegetables. Finally,this paper analyzes the effect of applying soil ecological remediation technology in overcoming obstacles to continuous cropping of vegetables.

Physiological Responses of Different Kinds of Vegetable Seedlings to Polycyclic Aromatic Hydrocarbons Stress

This study was conducted to explore the effects of polycyclic aromatic hydrocarbons (PAHs) on the growth and physiological characteristics of vegetable seedlings.Cucumber,Chinese cabbage and radish were cultured under the stress of 16 PAHs at different concentrations of 0.3,0.6 and 0.9 mg/L,respectively,with the seedlings cultured without PAHs as the control,to study the growth and physiological responses of various vegetable seedlings under PAHs stress.The results showed that the leaf width,fresh weight,CAT activity and POD activity of cucumber and the chlorophyll b content and CAT activity of radish reached the minimum values when treated with 0.3 mg/L PAHs.When the treatment concentration was 0.6 mg/L,the POD activity of cucumber,the vitamin C content of Chinese cabbage and the MDA content of radish were the smallest.The dry weight of cucumber,the fresh weight of Chinese cabbage and the fresh weight and POD activity of radish reached the minimums under the treatment of 0.9 mg/L PAHs.Different concentrations of PAHs could promote the synthesis and photosynthesis of chlorophyll in cucumber and Chinese cabbage leaves and the vitamin C content in radish.With the increase of PAHs treatment concentration,the MDA contents of cucumber and Chinese cabbage were on the increase,and reached the maximums under the treatment of 0.9 mg/L PAHs.One of the reasons why different kinds of vegetable seedlings have different physiological responses to PAHs may be related to the differences in the amount of PAHs absorbed by different leaf structures.

Adaptability Evaluation and Annual Production Model of Chinese Vegetable Varieties in Burundi

Burundi is one of the least developed countries identified by the United Nations.Vegetable is the main crop in Burundi,but the variety is relatively simple and the planting level is low.Making use of the rich vegetable varieties and advanced cultivation techniques in China,the adaptability evaluation of new vegetable varieties in China was jointly carried out in Burundi to screen the vegetable varieties suitable for local cultivation.The purpose of this paper is to study the integration of high-yield cultivation techniques and annual production model to improve the level of vegetable cultivation in Burundi.From 2009 to 2015,our unit,together with the Burundian Fruit and Vegetable Promotion Center,carried out screening experiments on 144 vegetable varieties,such as tomato,balsam pear,chieh-qua,wax gourd,and cabbage.Through the methods of preliminary screening and experimental screening,the vegetable varieties suitable for planting in Burundi were selected,and the cultivation techniques of some main vegetable varieties were studied.The demonstration new varieties and new techniques were integrated to verify the high-yield cultivation techniques in the field.In 2009,18 varieties suitable for local planting were selected from 96 vegetable varieties.In 2010,40 vegetable varieties were selected for screening test,and 9 varieties suitable for planting in Burundi were selected.In 2011,27 vegetable varieties selected in 2009 and 2010 were further evaluated for adaptability,and 13 vegetable varieties with high yield,strong resistance and good marketability were selected.Among them,there were 5 melon vegetables,3 solanaceous fruit vegetables,1 legume vegetables and 4 leafy vegetables.The cultivation techniques of some vegetable varieties were studied from 2011 to 2012,and the key points of cultivation techniques of chieh-qua and other vegetable varieties were clarified.According to the ecological characteristics of two main vegetable producing areas(the plateau and plain areas of Burundi),six sets of annual production and cropping arrangement plans covering melons,leafy vegetables,solanaceous fruits,beans and other vegetables were put forward,and the annual production model of multiple cropping and three-dimensional cultivation was integrated.From 2014 to 2015,according to the previous test results and market demand,8 vegetable varieties were selected for Burundi to carry out screening experiments.4 varieties with good yield and adaptability were selected for two consecutive years in 2014 and 2015.The integrated demonstration and effect verification of some selected vegetable varieties and cultivation techniques were carried out from 2015 to 2016,and the comprehensive advantages such as field yield and economic benefit were obvious.In this study,the adaptability of Chinese vegetable varieties in Burundi was evaluated,and 17 vegetable varieties suitable for local production were selected,including 5 melon vegetables,5 solanaceous fruit vegetables,1 legume vegetables and 6 leafy vegetables.This paper studies the integrated cultivation techniques and annual production model with obvious advantages in yield and benefit,which plays an important role in improving the planting level and benefit of vegetables in Burundi.

Fine-mapping and transcriptome analysis of the photosensitive leaf-yellowing gene CaLY1 in pepper(Capsicum annuum L.)

Leaf color is directly related to altered photosynthesis.Hence,leaf yellowing mutants can be widely used for the researching plant physiology and functional genomes,for cultivating new varieties of popular horticultural plants,and for identifying hybrid purity(as markers).Here,we constructed a^(60)Co-γF_(2)population from the leaf-yellowing mutant R24 via radiation mutation with the inbred line WT21 of pepper.Genetic analysis showed that the leaf-yellowing of the mutant was controlled by a single recessive gene.By applying the Bulk Segregation Analysis and Kompetitive Allele Specific PCR markers,the leaf-yellowing gene CaLY1(Capsicum annuum Leaf yellow 1)was mapped on chromosome 9,SNP5791587-SNP6011215,with a size of 214.5 kb.One non-synonymous mutated gene Capana09g000166 was found in the interval.The gene encoded a Psb X,which is the core complex of PSⅡ.Transcriptome analysis further showed that 2301 differentially expressed genes were identified under shading treatment for 24 h in R24.The Gene Ontology enrichment pathways were related to photosynthesis light harvesting,cell wall,activity of quercetin 3-O-glucosyltransferase and flavonoid metabolic process,which likely regulate the response of pepper leaves to different light levels.Functional enrichment analysis indicated that the most abundant pathways were photosynthesis antenna proteins and metabolic.

A novel single-base mutation in CaSGR1 confers the stay-green phenotype in pepper

The stay-green trait is of considerable importance in extending the shelf life of green pepper fruit(Capsicum annuum L.)and in enhancing the appearance of ornamental plants.The study revealed the genetic and regulatory mechanisms of the stay-green trait in pepper,which will aid in the selection of ornamental pepper varieties.In this study,a pepper mutant with stay-green fruit named TNX348 was identified from a germplasm resource bank.Two segregating populations were constructed using the stay-green mutant TNX348 and then used in bulked segregant analysis combined with RNA sequencing and linkage analyses.The causal gene of the stay-green trait was mapped to an approximately 131-kb region,and a senescence-induced chloroplast protein gene,CaSGR1(Capana01g000359),was identified as a candidate gene.Sequencing analysis revealed a G→A single-base mutation of CaSGR1 in TNX348 that led to early termination of translation.Based on the single-base mutation,a single nucleotide polymorphism(SNP)marker co-segregating with the stay-green trait was developed.Furthermore,in transcriptome analysis,expression patterns of 11 hormone transduction-related transcription factors,such as abscisic acid-insensitive(ABI),abscisic acidresponsive element-binding factor(ABF),and NAC transcription factor,were similar or opposite to that of CaSGR1.The results indicated that the transcription factors might mediate chlorophyll degradation by regulating the expression of CaSGR1.

Dissecting the genetic architecture of glucosinolate compounds for quality improvement in flowering stalk tissues of Brassica napus

Glucosinolates(GSLs) and their hydrolytic products contribute to the quality traits of rapeseed flowering stalk tissues, such as taste, flavor and anticarcinogenic properties(Glucoraphanin). However, little is known about the genetic mechanisms of GSL accumulation in rapeseed flowering stalks. In this study, the variation and genetic architecture of GSL metabolites in flowering stalk tissues were investigated for the first time among a panel of 107 accessions. All GSL compounds exhibited continuous and wide variations in the present population. Progoitrin,glucobrassicanapin and gluconapin were the most abundant GSL compounds. Five quantitative trait loci(QTL) significantly associated with three GSL compounds were identified by genome-wide association study. GRA_C04 was under selected during modern breeding, in which the ratio of lower GSL haplotype(HAP2) in the accessions bred before 1990(52.56%) was significantly lower than that after 1990(78.95%). Four candidate genes, BnaA01. SOT16, BnaA06. SOT17, Bna A06. MYB51a, and Bna A06. MYB51b, were identified in the GTL_A01 and 4OH_A06 regions.These findings provide new insights into GSL biosynthesis in flowering stalk tissues and facilitate quality improvement in rapeseed flowering stalks.

Mapping and validation of the epistatic D and P genes controlling anthocyanin biosynthesis in the peel of eggplant (Solanum melongena L.) fruit

Fruit color is an important trait inf luencing the commercial value of eggplant fruits.Three dominant genes(D,P and Y)cooperatively control the anthocyanin coloration in eggplant fruits,but none has been mapped.In this study,two white-fruit accessions(19141 and 19147)and their F2 progeny,with 9:7 segregation ratio of anthocyanin pigmented versus non-pigmented fruits,were used for mapping the D and P genes.A high-density genetic map was constructed with 5270 SNPs spanning 1997.98 cM.Three QTLs were identified,including two genes on chromosome 8 and one on chromosome 10.Gene expression analyses suggested that the SmANS on chromosome 8 and SmMYB1 on chromosome 10 were the putative candidate genes for P and D,respectively.We further identified(1)a SNP leading to a premature stop codon within the conserved PLN03176 domain of SmANS in 19141,(2)a G base InDel in the promoter region leading to an additional cis-regulatory element and(3)a 6-bp InDel within the R2-MYB DNA binding domain of SmMYB1,in 19147.Subsequently,these three variations were validated by PARMS technology as related to phenotypes in the F2 population.Moreover,silencing of SmANS or SmMYB1 in the purple red fruits of F1(E3316)led to inhibition of anthocyanin biosynthesis in the peels.Conversely,overexpression of SmANS or SmMYB1 restored anthocyanin biosynthesis in the calli of 19141 and 19147 respectively.Our findings demonstrated the epistatic interactions underlying the white color of eggplant fruits,which can be potentially applied to breeding of eggplant fruit peel color.

A novel mutation in ACS11 leads to androecy in cucumber

Sex determination in plants gives rise to unisexual flowers. A better understanding of the regulatory mechanism underlying the production of unisexual flowers will help to clarify the process of sex determination in plants and allow researchers and farmers to harness heterosis. Androecious cucumber(Cucumis sativus L.) plants can be used as the male parent when planted alongside a gynoecious line to produce heterozygous seeds, thus reducing the cost of seed production. The isolation and characterization of additional androecious genotypes in varied backgrounds will increase the pool of available germplasm for breeding. Here, we discovered an androecious mutant in a previously generated ethyl methanesulfonate(EMS)-mutagenized library of the cucumber inbred line ‘406’. Genetic analysis, whole-genome resequencing, and molecular marker-assisted verification demonstrated that a nonsynonymous mutation in the ethylene biosynthetic gene 1-AMINOCYCLOPROPANE-1-CARBOXYLATE SYNTHASE 11(ACS11) conferred androecy. The mutation caused an amino acid change from serine(Ser) to phenylalanine(Phe) at position 301(S301F). In vitro enzyme activity assays revealed that this S301F mutation leads to a complete loss of enzymatic activity. This study provides a new germplasm for use in cucumber breeding as the androecious male parent, and it offers new insights into the catalytic mechanism of ACS enzymes.

The root meristem growth factor BrRGF6 positively regulates Chinese cabbage to infection of clubroot disease caused by Plasmodiophora Brassicae

Chinese cabbage has a high annual demand in China.However,clubroot disease caused by the infection of Plasmodiophora brassicae seriously affects its yield.Transcriptome analysis identified a root meristem growth factor 6(BrRGF6)as significantly up-regulated in Chinese cabbage roots infected with Plasmodiophora brassicae.Quantitative reverse-transcription polymerase chain reaction and in situ hybridization analysis showed higher BrRGF6 expression in susceptible materials than in resistant materials.After Plasmodiophora brassicae infection,BrRGF6 expression was significantly up-regulated,especially in susceptible materials.Gene function analysis showed that the roots of Arabidopsis mutant rgf6 grew faster than the wild-type,and delayed the infection progress of Plasmodiophora brassicae.A Protein,nuclear transcription factor Y subunit C(BrNF-YC),was screened from yeast two-hybrid library of Chinese cabbage induced by Plasmodiophora brassicae,and verified to interact with BrRGF6 by yeast two-hybrid co-transfer.Yeast one-hybrid andβGlucuronidase activity analysis showed that BrNF-YC could directly bind to and strongly activate the promoter of BrRGF6.Transgenic verification showed that BrRGF6 or BrNF-YC silenced Chinese cabbage significantly decreased the expression of BrRGF6,accelerated root development,and reduced incidence of clubroot disease.However,after overexpression of BrRGF6 or BrNF-YC,the phenotype showed a reverse trend.Therefore,BrRGF6 silencing accelerated root growth and enhanced resistance to clubroot disease,which was regulated by BrNF-YC.

Genetic Analysis of the First Female Flower Node and the First Male Flower Node in Bitter Gourd

Exploring genetic mechanism of the first female flower node and the first male flower node in bitter gourd has practical significance for formulating breeding strategy. In this article, a cross was made between CN19-1 and Thai4-6, and the F2segregation population was also constructed through F1selfing. The genetic characteristics of the first female flower node and the first male flower node were analyzed by adopting the major gene plus polygene mixed genetic model. The data analysis results showed that the first female flower node and the first male flower node were continuous distribution in the F2segregation population. E-2 model was the most suitable model for the genetic analysis of the first female flower node and the first male flower node. The additive effect values of the 2 pairs of major genes controlling the first female flower node were 2.722 and 1.862 8 respectively, the dominant effect values were-2.721 6 and-0.171 8, respectively. The additive effect value of polygene was-0.839 2, and the dominant effect value of polygene was 2.225 4. The heritability of major genes and polygene were 83.73% and 1.54%, respectively. The additive effect values of the 2 pairs of major genes controlling the first male flower node were 17.746 9 and 3.972, respectively, the dominant effect values were 5.191 6 and-3.972, respectively. The additive effect value of polygene was-20.530 5, and the dominant effect value was-4.141 4. The heritability of major genes and polygene was 92.34% and 4.7%, respectively. This study could provide a theoretical basis for bitter gourd breeding.

Heritability of Main Yield Traits in Red-seed Watermelon and Their Correlation Analysis

[Objectives]This study was conducted to provide a reliable theoretical basis for the correct formulation of breeding programs for red-seed watermelon and the effective breeding of hybrid offspring.[Methods]With local varieties and inbred lines of red-seed watermelon as test materials,the generalized heritability of fruit number per plant,single-fruit weight,single-fruit seed number,single-fruit seed weight,seed kernel weight,1000-seed weight,kernel-producing ratio,seed production ratio and seed volume were estimated by variance analysis;and the heritability,genetic variation coefficients,and correlation of the nine yield traits in 43 red-seed watermelon varieties were studied.[Results]The generalized heritability of fruit number per plant,single-fruit weight,single-fruit seed number,single-fruit seed weight,seed kernel weight,1000-seed weight,kernel-producing ratio,seed production ratio and seed volume were 12.86%,80.14%,75.96%,74.39%,48.01%,17.12%,24.97%,18.60%,and 37.07%,respectively.The heritability of single-fruit weight,single-fruit seed number and single-fruit seed weight was higher,and early-generation individual selection could achieve a better effect on them;and 1000-seed weight and kernel-producing ratio had a higher coefficient of genetic variation,indicating a high selection potential.[Conclusions]Indirect selection could be achieved for traits such as the single-fruit seed number,single-fruit seed weight,seed kernel weight,and seed volume by selecting the single-fruit weight.In the process of red-seed watermelon breeding,traits with high heritability can be selected in early generations of hybrids,thus playing the role of early-generation orientation.

越南柑桔生产及种质资源

根据考察和学术交流收集到的资料,综述了越南柑桔生产概况、不同生态区柑橙生产情况、越南柑桔种质资源和商业化栽培的主栽柑桔品种特性,对促进中越柑桔学术交流具有重要的意义。

Genetic diversity and population structure analysis of Capsicum germplasm accessions

Genetic diversity plays an essential role in plant breeding and utilization.Pepper is an important vegetable and spice crop worldwide.The genetic diversity of 1 904 accessions of pepper conserved at the National Mid-term Genebank for Vegetables,Beijing,China was analyzed based on 29 simple sequence repeat(SSR)markers,which were evenly distributed over 12 pepper chromosomes.The pepper accessions were divided into two groups in a genetic structure analysis,and the two groups showed obvious differences in fruit type and geographical distribution.We finally selected 248 accessions capturing 75.6%of the SSR alleles as the core collection for further research.Insights into the genetic structure of pepper provide the basis for population-level gene mining and genetic improvement.

Effects of chitosan on growth of an aquatic plant (Hydrilla verticillata) in polluted waters with different chemical oxygen demands

Effects of chitosan on a submersed plant, HydriUa verticillata, were investigated. Results indicated that H. verticillata could prevent ultrastructure phytotoxicities and oxidativereaction from polluted water with high chemical oxygen demand （COD）. Superoxide dismutase （SOD） activity and malondialdehyde （MDA） contents in H. verticillata treated with 0.1% chitosan in wastewater increased with high COD （980 rag/L） and decreased with low COD （63 mg/L）, respectively. Ultrastructural analysis showed that the stroma and grana of chloroplast basically remained normal. However, plant ceils from the control experiment （untreated with chitosan） were vacuolated and the cell interval increased. The relict of protoplast moved to the center, with cells tending to disjoint. Our findings indicate that wastewater with high COD concentration can cause a substantial damage to submersed plant, nevertheless, chitosan probably could alleviate the membrane lipid peroxidization and ultrastructure phytotoxicities, and protect plant cells from stress of high COD concentration polluted water.

Comparative Transcriptome Analysis between Cytoplasmic Male-sterile Line and Its Maintainer During the Floral Bud Development of Pepper

The male-sterile line has been largely used in the hybrid seed production of pepper, which can effectively improve the efficiency of hybrid seed production. However, the formation mechanism of male sterility in pepper remains unclear. In the present study, we compared the gene expression patterns between pepper cytoplasmic male sterile line 9704 A and its maintainer 9704 B during floral bud development using RNA sequencing technology. A total of 547 976 and 2 416 Differentially Expressed Genes(DEGs) were identified in the stage S1, S2 and S3, respectively,and more than 70% of the DEGs were down-regulated in the sterile line. Gene Ontology(GO), and Kyoto Encyclopedia of Genes and Genomes(KEGG) enrichment analyses were performed to further understand the functions of these identified DEGs. The results showed that the DEGs were mainly enriched in pathways of starch and sucrose metabolism, pentose and glucuronate interconversions. A number of genes, such as MS1, PME5, ATPB, and lots of transcription factors were found down-regulated in the sterile line, and we also identified a series of genes with large differences in expression patterns between sterile line and maintainer line. Collectively, our findings laid a foundation for further molecular breeding in pepper and provided new insights into its mechanism underlying the male sterility.

Draft genome sequence of cauliflower(Brassica oleracea L.var.botrytis)provides new insights into the C genome in Brassica species

Cauliflower is an important variety of Brassica oleracea and is planted worldwide.Here,the high-quality genome sequence of cauliflower was reported.The assembled cauliflower genome was 584.60 Mb in size,with a contig N50 of 2.11 Mb,and contained 47,772 genes;56.65%of the genome was composed of repetitive sequences.Among these sequences,long terminal repeats(LTRs)were the most abundant(32.71%of the genome),followed by transposable elements(TEs)(12.62%).Comparative genomic analysis confirmed that after an ancient paleohexaploidy(γ)event,cauliflower underwent two whole-genome duplication(WGD)events shared with Arabidopsis and an additional whole-genome triplication(WGT)event shared with other Brassica species.The present cultivated cauliflower diverged from the ancestral B.oleracea species~3.0 million years ago(Mya).The speciation of cauliflower(~2.0 Mya)was later than that of B.oleracea L.var.capitata(approximately 2.6 Mya)and other Brassica species(over 2.0 Mya).Chromosome no.03 of cauliflower shared the most syntenic blocks with the A,B,and C genomes of Brassica species and its eight other chromosomes,implying that chromosome no.03 might be the most ancient one in the cauliflower genome,which was consistent with the chromosome being inherited from the common ancestor of Brassica species.In addition,2,718 specific genes,228 expanded genes,2 contracted genes,and 1,065 positively selected genes in cauliflower were identified and functionally annotated.These findings provide new insights into the genomic diversity of Brassica species and serve as a valuable reference for molecular breeding of cauliflower.