The late-bolting genes in radish were localized,and the candidate genes regulating flowering were explored. The main results are listed below:a high-density genetic linkage map was constructed and two QTL loci related to flowering and bolting were detected. Based on radish gene annotation and gene sequence alignment analysis,we detected five genes with the sequence variation between the parental lines,indicated those genes associated with bolting and flowering in radish. However,the detailed functions of the candidate gene during the radish bolting and flowering need further studies.
The InDel marker for genetic background selection is beneficial to the efficient selection of Chinese cabbage breeding parents. Taking 31 inbred lines of Chinese cabbage with different ecological types as materials,InDel genetic background and association of agronomic traits were analyzed in this study. The results showed that the coefficient of variation of 31 agronomic traits varied from 15.97% to 47.63%,with an average of 32.58%,indicating that the phenotypic diversity of tested population was rich. Finally,158 polymorphic primer pairs were selected from 177 InDel primer pairs. A total of 701 polymorphic alleles were detected in 31 accessions of Chinese cabbage,with an average of 4.418 alleles per primer pair,ranging from 1 to 11. The polymorphic information content(PIC)of the marker loci ranged from 0.612 to 0.963,with an average of 0.843,and the number of effective alleles(Ne)ranged from 1.656 to 3.985,averagely 2.640. The genetic similarity coefficient(GS)of tested materials of Chinese cabbage varied greatly from 0.575 to 0.910,indicating that the genetic background of the population was quite different. According to population structure analysis,tested materials were divided into three subgroups. Association analysis showed that 22 InDel molecular markers distributed in nine linkage groups related to 12 agronomic traits,including expansion spreading,whole plant weight,head leaf number,outer leaf number,leaf width,leaf length,leaf head height,leaf head width,leaf head weight,middle rib length,central column length and plant height.
Referring to the SSR molecular markers of chromosome F linkage group in the chromosome-assigned sequence-tagged linkage map of radish,two SSR molecular markers RM-59-293 and Rs1SSR3694-220 which were specific for radish chromosome F were confirmed by means of the known radish-chromosome information in the genetic background of 21 materials. Both SSR markers were used to identify the alien radish chromosome F in the genetic background of BC1 being derived from the backcross of Brassica rapa‘559’and rape-radish chromosome F addition line FF. As a result,10 BC1 plants added with alien radish chromosome F were obtained. Furthermore,the genome of the selected 10 BC1 plants with radish chromosome F were analyzed to detect the exogenous radish chromosome by fluorescence in situ hybridization technology using the radish genomic probe pURsN. The result showed that all of the 10 BC1 had one hybridization signal,which indicated that each of the tested BC1 plants was added with an exogenous radish chromosome. The main agronomic traits of the 10 BC1 plants were further identified. As a result,BC1-15 with the morphology similar to Chinese cabbage parent‘559’and BC1-8,BC1-16,BC1-31 and BC1-35 with the morphology partial to Chinese cabbage were selected.
Present study synthesized the ABC genomic plant by interspecific hybridization and embryo rescue using pakchoi(Brassica rapa ssp. chinensis,AA genome)as maternal and Ethiopian mustard(Brassica carinata,BBCC genome),which originated from Africa and was immune to black rot. The hybrid plant showed strong heterosis at the vegetative growth stage. The genomic composition was confirmed by molecular markers and flow cytometry analysis. The F1 plants were sterile at beginning but gradually restored the fertility after several generation of tissue culture and propagation. The fertility restoration is faster in the backcross progeny with Ethiopian mustard than that with pakchoi. Flow cytometry analysis indicated that the chromosomal contents of the F1 and backcross progeny distributed in the interval of pakchoi and Ethiopian mustard. The automatic chromosomal doubling was observed in the leaf tissue cells. The abnormal chromosome behaviors include non reduction,chromosome lagging,asymmetric segregation,chromosome stickiness and chromosome bridges were revealed in the pollen mother cells. The black rot immune or high resistant lines were screened from the backcross progeny of the synthesized ABC with pakchoi plants. The resistance was inheritable.
In this study,Bulked Segregant Analysis Sequencing(BSA-seq)was conducted on two Chinese cabbage populations,named as 1E519BC1F2 and 4E511BC1F2. We identified a common candidate region from the above two populations,which located on 7.40-8.85 Mb of chromosome A08. Here,we named this region as BraA.Pb.8.4. BraA.Pb.8.4 might be a novel clubroot resistance gene for two reasons. Firstly,in terms of physical position,BraA.Pb.8.4 is distinct from previous reported genes,Crr1,Rcr9 and CRs. Secondly,markers linked to Crr1 and Rcr9 amplified the same product without length polymorphysims between resistant and susceptible materials,and only one of the four CRs linked markers (Probe60)produced polymorphysims. Among the candidate region of BraA.Pb.8.4,three KASP markers,BraA.Pb.8.4-K1,BraA.Pb.8.4-K2 and BraA.Pb.8.4-K3,were developed. These three KASP markers are co-dominant markers which can not only effectively separate homozygous resistant genotypes from the homozygous susceptible genotypes,but also distinguish the heterozygous genotypes. Marker BraA.Pb.8.4-K1 were further genotyped in a total of 257 individuals,which belongs to five populations. The results showed that the average consistency rate between genotypes and phynotypes of the above 257 individuals was high to 96.13%. Thus,the BraA.Pb.8.4 gene and the KASP markers developed here can be efficently used for marker-assisted selection(MAS)of clubroot resistant gene in breeding.
In order to excavate key regulatory genes for irregular fruit cracking in tomato,the F1 and F2 offspring were obtained by crossing the cracking-susceptible(CS)germplasm accession‘S189’and the cracking-resistant(CR)germplasm accession‘R91’and subsequent self-crossing. QTL-seq approach was applied to identify candidate QTLs. Genomic DNA of 20 CS and 20 CR F2 individuals were evenly mixed as CS-pool and CR-pool,respectively. A total of two QTLs that regulated irregular fruit cracking in tomato were detected,which were physically located in the region of 38.75-42.14 Mb on chromosome 2 and the region of 49.07-49.48 Mb on chromosome 5. The two QTLs were temporarily designated as qCR2 and qCR5. In view of the fact that there were only two genes in the region of qCR5,the differences at gene expression levels were analyzed using the mature fruit pericarps from the parents. However,both the results showed no significant differences between the parents. Considering that the region of qCR2 was relatively large,in order to quickly and effectively mine candidate genes,the linkage map of chromosome 2 was constructed using 43 polymorphic markers. Afterwards,traditional QTL analysis was carried out based on the fruit cracking rate of F2 population. A major QTL was detected between the polymorphic markers sli2734 and Bin3371,whose LOD score was 3.05 and contribution rate was 7.05%. The corresponding physical location of the major QTL was coincided with the qCR2’s region. According to the results from both QTL-seq and traditional QTL analysis,the candidate region was delimited between 39.55-39.94 Mb,eventually designated as qCR2.1. There were a total of 53 genes in qCR2.1’s region. Accordingly,the mature fruit pericarps from the parents were used to analyze the differences at gene expression levels and thus three genes with significantly different expression levels were obtained,namely Solyc02g072400,Solyc02g072470 and Solyc02g076780. Among them,the expression levels of Solyc02g076780 between the parents were extremely significantly different. Solyc02g076780 played a role in ethylene regulation,which could be a key candidate gene for irregular fruit cracking in tomato.
We measured and analyzed internode length at the third panicle of 266 tomato accessions. Seven QTL related to tomato internode length were identified by genome-wide association study. Candidate genes were analyzed based on the significant SNPs in chromosomes 10 and 11. The IL10(Forkhead- associated domain protein)and IL11(Auxin-regulated protein)related to the internode length were further excavated. Tomato‘Ailsa Craig’was used as the background material. 11 IL10-RNAi lines and 10 IL11-RNAi lines were obtained by Agrobacterium-mediated transformation. The internode length of IL10- and IL11-silencing transgenic lines was significantly shorter than that of the wild type. To sum up,IL10 and IL11 are the key genes that positively regulates tomato internode length.
Alien addition lines are important interspecific materials,which can be used for introgression of interspecific genetic material and gene mapping. Creating a variety of alien addition lines plays an important role in cultivar improvement and related research of cucumber. In this experiment,based on the allotetraploid Cucumis hytivus from the cross of C. sativus and C. hystrix,two backcrosses with diploid cultivar C. sativus were carried out to obtain 22 plants of BC2. The plant containing alien chromosome in BC2 population was identified by GISH technique. Further,oligo-FISH technology and 12 C. hystrix chromosome specific single-copy sequence markers were used to accurately identify the alien chromosomes. Finally,a total of four different alien additional lines were screened,including three monosomic alien addition lines(MAALs)which contained C. hystrix chromosomes H06,H10,and H12,respectively,and one double alien monosomic addition line containing H06 and H10.
We isolated a natural mutant,msf(medium short-fruit),from the cucumber inbred line CCMC,a North China type with long fruits. The mutant showed the phenotype of shorter fruit length and fruit neck length than the wild type and also showed short plant,abnormal development of lateral branches and fragile main stem. Through paraffin section and scanning electron microscope observation,it was found that the difference of mutant fruit length was caused by the change of cell size. Genetic analysis showed that the segregation ratio of wild-type phenotype long fruit and mutant phenotype medium short fruit in F2 segregation population conformed to Mendel’s 3︰1 genetic law. This indicated that msf mutation was a recessive trait controlled by a single gene. BSA-seq analysis showed that the candidate gene was located in a 26.7-30.9 Mb region of chromosome 1 of cucumber genome. The msf gene was mapped to a 28.4-29.8 Mb region using a F2 population containing 437 individuals from a cross between msf and ‘hazerd’(a European greenhouse-type inbred line with short fruit). CsaV3_1G044310 was identified as the candidate gene by genome-wide screening combined with dCAPS marker verification,which encodes a homologous protein of Arabidopsis type Ⅱ inositol polyphosphate 5-phosphatase(type Ⅱ 5 Ptase). The quantitative expression of gene and the determination of endogenous hormones auxin and gibberellin the mutant may cause the change of hormone levels and affect the growth and development of plant.
In this study,231 cucumber core germplasms collected from the world were used for resistance identification of powdery mildew in Beijing and Guangzhou in 2017 and 2018,respectively. A total of 950 382 SNPs detected by genome re-sequencing were used for genome-wide association analysis. The results showed that the natural incidence of cucumber powdery mildew in Guangzhou was significantly higher than that in Beijing. High correlation was detected between the two-year disease index among different germplasms. Based on the mixed linear model,12 significantly associated signals were detected,and they distributed on chromosomes 1,5 and 6. Among them,pm1.1 was detected repeatedly in two-year in Beijing,while pm5.7 was detected repeatedly in two-year in Guangzhou. These significantly associated signals contained 68 SNPs that exceeded the threshold of-log10(P value) with 6.0. Among them,a non-synonymous mutant SNP(Chr5:16 676 542)located on the exon of xenotropic and polytropic retrovirus receptor(Csa5G471600). A total of 63 candidate genes were found in the LD block of SNPs associated with powdery mildew resistance,among which seven candidate genes showed significant differential expression after being infected with powdery mildew in the cucumber material with high resistance.
To realize the accurate molecular identification for fruit shape,we performed following study. Based on resource advantage of“National mid-term gene-bank for watermelon and melon”and re-sequencing platform,two segregation populations,including an F2 and an BC1P1,has been constructed to unravel the functional genetic variation for fruit shape in watermelon. A 159 bp InDel(Insertion/Deletion)and one non-synonymous SNP led round fruit to long fruit in watermelon,respectively. Moreover,the SNP located on the genomic region of 159 bp InDel. One CAPS marker,Markersun,was developed and genotyped in F2 and BC1P1 populations,and a core germplasm resources including 128 inbred lines. The marker Markersun showed InDel and SNP polymorphism in F2 and BC1P1 populations,respectively,and totally cosegregated with fruit shape variation in both populations. The marker Markersun both showed InDel and SNP polymorphism in core germplasm resources and totally cosegregated with fruit shape variation. The results were reconfirmed based on resequencing data of 196 germplasm resources in watermelon. Moreover,genotype analysis of different type of germplasms found that long fruit caused by SNP occurred earlier and inherited independently;while long fruit caused by 159 bp InDel occurred during domestication of cultivated watermelon. The current research firstly realized accurate molecular identification of watermelon fruit shape. At the same time,two functional variations of fruit shape were excavated and corresponding marker was developed to accurately identify watermelon fruit shape. These results will provide technical support and targets for the functional verification of fruit shape traits,and accelerate the study of the functional mechanism for fruit shape gene in watermelon.
In this study,we revealed the genetic diversity,principal coordinate analysis and population structure analysis of 676 garlic accessions from all over the word by using 24 pairs of selected primers. The results indicate that a total of 124 polymorphic sites were detected,with an average of 5.17 alleles,an average of 1.77 for Nei's diversity index and 0.62 for Shannon information index. The mean values of observed and expected heterozygosity were 0.33 and 0.34,respectively. The method of neighbor-joining clustered all the accessions into four groups,group Ⅰ included 186 accessions,most of which were derived from middle and high latitudes of Asia,group Ⅱ included 205 accessions,most of which were derived from Europe,Central Asia and North America,group Ⅲ included 132 accessions,most of which were half-bolting types from Asia,group Ⅳ included 153 accessions,most of which were derived from lower latitudes of Asia. The garlic population was divided into three groups by principal coordinate analysis,accessions from lower latitude of Asia gathered in group Ⅰ and group,accessions from middle and high latitudes of Asia,Europe,North America area gathered in group Ⅱ. Population structure analysis divided the germplasm into four groups,which were similar to cluster analysis,there was gene exchange among different garlic groups. The genetic diversity and Shannon's diversity information index of germplasm resources from Europe,Central Asia and North America were the highest,which were 0.3213 and 0.5933,respectively,indicating that this population had rich genetic diversity. The method of neighbor-joining cluster analysis and population genetic structure analysis divided 382 Chinese resources into four groups,mainly from North China,South China,Mongol Xinjiang and Southwest China,respectively. The germplasm of North and South China was distributed at both ends of PC1 by principal coordinate analysis,showing a distant phylogenetic relationship. The results can provide scientific basis for the identification and evaluation of garlic germplasm and the breeding of superior garlic varieties.
In the present study,the process of garlic(Allium sativum)clove development was observed and analyzed through freehand anatomy and paraffin embedded. The morphological observation showed that there were three stages,including the pre-differentiation stage,differentiationstage and expansion stage for clove development before mature. At the pre-differentiation stage,the leaf primordia with typical tunica-corpus structure was formed. At the differentiation stage,small clove formed. The location of small clove formation was related to the location of meristematic cell mass. The internal growth points of the formed scale clove continued to differentiate with the accumulation of clove material. At the expansion stage,the chromosomes in the meristematic nuclei were active,starch grains were accumulated in the meristematic cell mass and the vessels had developed well in xylem. To observe the tissue histochemical changes,PAS staining was carried out on the sections from different parts of the clove at the differentiation stage. The content of sugar granules was rich,the cytoplasm was dense and the staining was dark. The concentration gradient of sugar granules existed between the meristematic cells and their surrounding cells.
Allium L. is an important perennial herb,which is one of the largest genera in monocotyledoneae Liliaceae,and widely distribute all over the world. To understand the Allium clearly,the systematic classification,interspecific differentiation,and genetic relationship are very important. However,it is very difficult to clarify for the Allium plant due to the large group. This article summarized the research progress of Allium including the discovery,plant system location,new taxonomic category within the genus and systematic taxonomy. The systematic position of Allium plants was also constantly changing because of the different classification standards. There were three main points of view on the evolution of its historical location. It was believed that the Allium belongs to the Liliaceae family,or Amaryllidaceae family,or Alliaceae family. Although there were different views on the systematic location of Allium plants,most scholars suggested the Allium as the genus and the subgenus,the group and other classification methods should be used as subunits. Nowadays,the research progress on the systematic taxonomy of Allium mainly focuses on phenotypic traits,pollen micromorphology,seed coat micromorphology,cytology and molecular systematics. At the molecular level,nuclear genome sequences and chloroplast genome sequences have been used in the taxonomic study of Allium plants,but mitochondrial genome sequences have not been reported. In the future,research on the classification of Allium plants,the combination of multiple methods will surely become a trend,which can identify and classify Allium species faster and more accurately.
‘Chunyou 4’is a new pakchoi F1 hybrid developed by crossing two self-incompatible lines 120754 and 120758. The plant type is erect. The plant is 20.2 cm in height and 19.5 cm in width after 50 days of sowing in spring cultivation. The leaf is flat,green and shiny,with 12 cm in width. The number of blades is nine. The petiole is green,less wax powder,with 4.3 cm in width and 0.83 cm in thickness. The single plant weight is about 0.19 kg. It is resistant to TuMV,black rot and downy mildew. It is tolerant to late-bolting with good commodity. It is suitable for cultivated in Beijing,Tianjin,Hebei,Shandong,Liaoning,Shaanxi,Gansu,Jiangsu,Shanghai,Anhui and other provinces at solar greenhouse in winter and open field in spring cultivation.
The new South China cucumber cultivar‘Lifeng 2’is a hybrid which was crossed strong female inbred line g-13 with the heat-resistant and disease-resistant inbred line g-48. This cultivar grows vigorously,and it has strong fruit-setting ability. Its fruit is cylindrical. This cultivar has green skin with stripes,fragrant flavor,good quality. The fruit length,transverse diameter,flesh thickness and single fruit weight is 22.5 cm,5.3 cm,1.3 cm and 400 g,respectively. This cultivar is resistant to disease,storage and transportation. The yield can reach up to 65 000 kg · hm-2. It is suitable for planting in spring and autumn in South China and Southeast Asia.
‘Zhongsuan 1’is a new garlic cultivar which was selected from a natural mutant plant among the local cultivar 8N141 through multi-year continuous propagation and identification of important traits.‘Zhongsuan 1’has mid-late maturity. The bulb skin of is purple and garlic bulb transverse diameter is about 5-7 cm. The average fresh weight of bulb is 80-125 g. The yield is about 24.15 t · hm-2. It has high tolerance to cold environment,and it is suitable for open field cultivation in the northern region.
‘Jingmei 10K’is a new mid-maturing watermelon cultivar. The fruit is short oval with heavy wax,the fruit index is 1.2. The fruit has durable rind for transportation,which is green with narrow dark green strips,about 1.2 cm thick. The fruit is uniform in shape with high commodity rate. The flesh is bright red with 50.5 mg · kg-1 FW lycopene content,and its center soluble solids content is 13%. It is crisp with good taste and less watery flesh,and it can turn color fast. The total growing period is about 95 d and the fruit development period is about 35 d. The average fruit weight is 10 kg and the yield is about 75 000 kg · hm-2. It is suitable for protected and open field cultivation in spring.