Investigation of genomic organization in switchgrass (Panicum virgatum L.) using DNA markers

We report an early investigation into genomic organization and chromosomal transmission in switchgrass based on restriction fragment length polymorphism (RFLP) markers. The segregation of 224 single dose restriction fragments (SDRF) in 85 full-sib progeny of a cross between the genotypes Alamo (AP13) and Summer (VS16) was used to determine linkage associations in each parent. In the seed parent AP13, 11 cosegregation groups were identified by 45 SDRF markers with a cumulative recombination length of 412.4 cM. In the pollen parent VS16, 57 SDRF markers were assigned to 16 cosegregation groups covering a length of 466.5 cM. SDRF markers identified by the same probes and mapping to different cosegregation groups were used to combine the two maps and identify homology groups. Eight homology groups were identified among the nine haploid linkage groups expected in switchgrass. The high incidence of repulsion phase associations indicates that preferential pairing between homologous chromosomes is predominant in switchgrass. Based on marker distribution in the paternal map (VS16), we estimated the recombinational length of switchgrass genome to be 4,617 cM. In order to link 95% of the genome to a marker at a 15-cM distance, a minimum of 459 markers will be required. Using information from the ratio of repulsion to coupling linkages, we infer that switchgrass is an autotetraploid with a high degree of preferential pairing. The information presented in this study establishes a foundation for extending genetic mapping in this crop and constitutes a framework for basic and applied genetic studies.Electronic Supplementary Material Supplementary material is available for this article at     

New genetic maps for globe artichoke and wild cardoon and their alignment with an SSR-based consensus map

An F1 mapping population was bred by crossing an accession of wild cardoon with a single Argentinian globe artichoke plant of the variety Estrella del Sur FCA with a view to generating new Cynara cardunculus linkage maps. Genotyping was conducting using a set of 553 SRAP, SSR, AFLP and SNP markers. The 1,465.5 cM map based on the segregation of alleles present in the wild cardoon parent comprised 214 loci distributed across 16 linkage groups (LGs), while the 910.1 cM globe artichoke-based map featured 141 loci falling into 12 LGs covering the total length. Three of the morphological traits (head spininess, leaf spininess and head color) for which the parents contrasted were inherited monogenically, and the genes conditioning them were mapped. A set of 48 co-dominant loci was used to align the LGs with those derived from a reference SSR-based consensus map of the species.     

An SSR- and AFLP-based genetic linkage map of tall fescue (Festuca arundinacea Schreb.)

Tall fescue (Festuca arundinacea Schreb.) is commonly grown as forage and turf grass in the temperate regions of the world. Here, we report the first genetic map of tall fescue constructed with PCR-based markers. A combination of amplified fragment length polymorphisms (AFLPs) and expressed sequence tag-simple sequence repeats (EST-SSRs) of both tall fescue and those conserved in grass species was used for map construction. Genomic SSRs developed from Festuca × Lolium hybrids were also mapped. Two parental maps were initially constructed using a two-way pseudo-testcross mapping strategy. The female (HD28-56) map included 558 loci placed in 22 linkage groups (LGs) and covered 2,013 cM of the genome. In the male (R43-64) map, 579 loci were grouped in 22 LGs with a total map length of 1,722 cM. The marker density in the two maps varied from 3.61 cM (female parent) to 2.97 (male parent) cM per marker. These differences in map length indicated a reduced level of recombination in the male parent. Markers that revealed polymorphism within both parents and showed 3:1 segregation ratios were used as bridging loci to integrate the two parental maps as a bi-parental consensus. The integrated map covers 1,841 cM on 17 LGs, with an average of 54 loci per LG, and has an average marker density of 2.0 cM per marker. Homoeologous relationships among linkage groups of six of the seven predicted homeologous groups were identified. Three small groups from the HD28-56 map and four from the R43-64 map are yet to be integrated. Homoeologues of four of those groups were detected. Except for a few gaps, markers are well distributed throughout the genome. Clustering of those markers showing significant segregation distortion (23% of total) was observed in four of the LGs of the integrated map.Electronic Supplementary Material Supplementary material is available for this article at     

Constructing genetic linkage maps for Pinus elliottii var. elliottii and Pinus caribaea var. hondurensis using SRAP, SSR, EST and ISSR markers

A total of 122 F₁ individuals from a single full-sib interspecific hybrid family crossed between Pinus elliottii var. elliottii (PEE) and P. caribaea var. hondurensis (PCH) were used to construct a detailed genetic linkage maps using four types of molecular markers: sequence-related amplified polymorphism (SRAP), microsatellite (SSR), expressed sequence tag polymorphism (ESTP) and inter-simple sequence repeat (ISSR). There were 381 SRAP, 108 SSR, 25 ESTP and 32 ISSR loci, segregating in the interspecific F₁ hybrid individuals. Framework maps were constructed at a LOD score threshold of 4.0 using the JoinMap^® 3.0. The map for the male parent (PCH) had 108 markers in 16 linkage groups (LGs), with a total length of 1,065.9 cM (Kosambi) and an average marker interval of 9.87 cM. The map for the female parent (PEE) contained 93 markers in 19 LGs, with a total length of 1,006.7 cM (Kosambi) and an average marker interval of 10.82 cM. The maps for PCH and PEE covered 56.5 and 70.3 % of their respective genomes. Based on the position of 36 loci segregating in both parents, 8 homologous LGs between PEE and PCH were identified.     

Linkage maps of microsatellite DNA markers for the Pacific oyster Crassostrea gigas

We constructed male and female consensus linkage maps for the Pacific oyster Crassostrea gigas, using a total of 102 microsatellite DNA markers typed in 11-day-old larvae from three families. We identified 11 and 12 linkage groups in the male and female consensus maps, respectively. Alignment of these separate maps, however, suggests 10 linkage groups, which agrees with the haploid chromosome number. The male linkage map comprises 88 loci and spans 616.1 cM, while the female map comprises 86 loci and spans 770.5 cM. The male and the female maps share 74 loci; 2 markers remain unlinked. The estimated coverages for the consensus linkage maps are 79% for the male and 70-75% for the female, on the basis of two estimates of genome length. Ninety-five percent of the genome is expected to lie within 16 and 21 cM of markers on the male and female maps, respectively, while 95% of simulated minimum distances to the male and female maps are within 10.1 and 13.6 cM, respectively. Females have significantly more recombination than males, across 118 pairs of linked markers in common to the parents of the three families. Significant differences in recombination and orders of markers are also evident among same-sex parents of different families as well as sibling parents of opposite sex. These observations suggest that polymorphism for chromosomal rearrangements may exist in natural populations, which could have profound implications for interpreting the evolutionary genetics of the oyster. These are the first linkage maps for a bivalve mollusc that use microsatellite DNA markers, which should enable them to be transferred to other families and to be useful for further genetic analyses such as QTL mapping.     

High‐density linkage map reveals QTL underlying growth traits in AP13×VS16 biparental population of switchgrass

Switchgrass (Panicum virgatum L.), a native warm‐season perennial grass, is being considered as a feedstock for biofuel production in the United States. To expedite its genetic improvement and enhance genetic gain per selection cycle, application of marker‐assisted selection is indispensable. A high‐density linkage map was constructed in a pseudo‐F₁ testcross mapping population of AP13×VS16, consisting of 349 progenies. A total of 8,757 single nucleotide polymorphism (SNP) markers generated through genotype‐by‐sequencing (GBS) were used to construct the linkage map. The total map length spans up to 2,540.2 cM with the marker density of one marker in every 0.25–0.34 cM. Spring green‐up (SG), days to flowering (FL), and the vegetative growth period (VP) data were analyzed and used for quantitative trait loci (QTL) mapping. The population showed significant variations and exhibited transgressive segregation for SG, FL, and VP. QTL analyses were performed using trait mean of each year and location along with BLUP (best linear unbiased prediction) values of the traits. A total of 35, 37, and 34 QTL for SG, FL, and VP, respectively, were identified. Phenotypic variability explained by each QTL ranged from 11.29% to 27.85%. The additive genetic effects of individual QTL ranged from ?1.81 to 2.40, ?6.12 to 7.58, and ?16.01 to 6.38 for SG, FL, and VP, respectively. Comparing major QTL regions in the switchgrass genome, 20 candidate genes were identified which were reported to be involved in growth‐, development‐, and flowering‐related traits in switchgrass.     

Genetic maps of SSR and SRAP markers in diploid orchardgrass (Dactylis glomerata L.) using the pseudo-testcross strategy

Orchardgrass (Dactylis glomerata L.) is one of the most important cool-season forage grasses commonly grown throughout the temperate regions of the world. The objective of this work was to construct a diploid (2n = 2x = 14) orchardgrass genetic linkage map useful as a framework for basic genetic studies and plant breeding. A combination of simple sequence repeat (SSR) and sequence-related amplified polymorphism (SRAP) molecular markers were used for map construction. The linkage relationships among 164 SSRs and 108 SRAPs, assayed in a pseudo-testcross F1 segregating population generated from a cross between two diploid parents, were used to construct male (01996) and female (YA02-103) parental genetic maps. The paternal genetic map contains 90 markers (57 SSRs and 33 SRAPs) over 9 linkage groups (LGs), and the maternal genetic map is composed of 87 markers (54 SSRs and 33 SRAPs) assembled over 10 LGs. The total map distance of the male map is 866.7 centimorgans (cM), representing 81% genome coverage, whereas the female map spans 772.0 cM, representing 75% coverage. The mean map distance between markers is 9.6 cM in the male map and 8.9 cM in the female map. About 14% of the markers remained unassigned. The level of segregation distortion observed in this cross was 15%. Homology between the two maps was established between five LGs of the male map and five LGs of the female map using 10 bridging markers. The information presented in this study establishes a foundation for extending genetic mapping in this species, serves as a framework for mapping quantitative trait loci (QTLs), and provides basic information for future molecular breeding studies.     

Development of genetic maps of the citrus varieties ‘Murcott’ tangor and ‘Pêra’ sweet orange by using fluorescent AFLP markers

The progeny of 87 BC(1) hybrids of 'Murcott' tangor and 'Pera' sweet orange, genotyped with fluorescent amplified fragment length polymorphism (fAFLP) markers, was used for the construction of genetic maps for both citrus varieties. Mapping strategies, considering the progeny as a result of backcrossing and cross-pollination, were exploited in Mapmaker 2.0 (LOD score >or= 3.0 and or= 3.0 and theta 相似文献   

Linkage analysis and identification of quantitative trait loci associated with freeze tolerance and turf quality traits in St. Augustinegrass

St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] is a warm-season turfgrass commonly grown in the southern USA. In this study, the first linkage map for all nine haploid chromosomes of the species was constructed for cultivar ‘Raleigh’ and cultivar ‘Seville’ using a pseudo-F₂ mapping strategy. A total of 160 simple sequence repeat markers were mapped to nine linkage groups (LGs) covering a total distance of 1176.24 cM. To demonstrate the usefulness of the map, quantitative trait loci (QTL) were mapped controlling field winter survival, laboratory-based freeze tolerance, and turf quality traits. Multiple genomic regions associated with these traits were identified. Moreover, overlapping QTL were found for winterkill and spring green up on LG 3 (99.21 cM); turf quality, turf density, and leaf texture on LG 3 (68.57–69.50 cM); and surviving green tissue and regrowth on LGs 1 (38.31 cM), 3 (77.70 cM), 6 (49.51 cM), and 9 (34.20 cM). Additional regions, where QTL identified in both field and laboratory-based/controlled environment freeze testing co-located, provided strong support that these regions are good candidates for true gene locations. These results present the first complete linkage map produced for St. Augustinegrass, providing a template for further genetic mapping. Additionally, markers linked to the QTL identified may be useful to breeders for transferring these traits into new breeding lines and cultivars.     

RAPD-based genetic linkage maps of yellow passion fruit (Passiflora edulis Sims. f. flavicarpa Deg.).

A single cross between two clones of passion fruit (Passiflora edulis Sims. f. flavicarpa Deg., 2n = 18) was selected for genetic mapping. The mapping population was composed of 90 F1 plants derived from a cross between 'IAPAR 123' (female parent) and 'IAPAR 06' (male parent). A total of 380 RAPD primers were analyzed according to two-way pseudo-testcross mapping design. The linkage analysis was performed using Mapmaker version 3.0 with LOD 4.0 and a maximum recombination fraction (theta) of 0.30. Map distances were estimated using the Kosambi mapping function. Linkage maps were constructed with 269 loci (2.38 markers/primer), of which 255 segregated 1:1, corresponding to a heterozygous state in one parent and null in the other. The linkage map for 'IAPAR123' consisted of 135 markers. A total of nine linkage groups were assembled covering 727.7 cM, with an average distance of 11.20 cM between framework loci. The sizes of the linkage groups ranged from 56 to 144.6 cM. The linkage map for 'IAPAR 06' consisted of 96 markers, covering 783.5 cM. The average distance between framework loci was 12.2 cM. The length of the nine linkage groups ranged from 20.6 to 144.2 cM. On average, both maps provided 61% genome coverage. Twenty-four loci (8.9%) remained unlinked. Among their many applications, these maps are a starting point for the identification of quantitative trait loci for resistance to the main bacterial disease affecting passion fruit orchards in Brazil, caused by Xanthomonas campestris pv. passiflorae, because parental genotypes exhibit diverse responses to bacterial inoculation.     

Construction of a genetic linkage map in Fenneropenaeus chinensis using SNP markers

Genetic linkage maps of Fenneropenaeus chinensis were constructed using a “double pseudo-testcross” strategy with 200 single nucleotide polymorphisms (SNPs) markers. This study represents the first SNP genetic linkage map for F. chinensis. The parents and F ₁ progeny of 100 individuals were used as mapping populations. 21 genetic linkage groups in the male and female maps were identified. The male linkage map was composed of 115 loci and spanned 879.7 cM, with an average intermarker spacing of 9.4 cM, while the female map was composed of 119 loci and spanned 876.2 cM, with an average intermarker spacing of 8.9 cM. The estimated coverage of the linkage maps was 51.94% for the male and 53.77% for the female, based on two estimates of genome length. The integrated map contains 180 markers distributed in 16 linkage groups, and spans 899.3 cM with an average marker interval of 5.2 cM. This SNP genetic map lays the foundation for future shrimp genomics and genetic breeding studies, especially the discovery of gene or regions for economically important traits in Chinese shrimp.     

A preliminary microsatellite genetic map of the ostrich (Struthio camelus)

Molecular genetic maps can provide information for the identification and localization of major genes associated with quantitative traits. However, there are currently no published genetic linkage maps for any ratites. Herein, a preliminary genetic map of ostrich was developed using a two-generation ostrich reference family by linkage analysis of 104 polymorphic microsatellite markers, including 40 novel markers reported in this study. A total of 35 microsatellite markers were placed into 13 linkage groups. Five linkage groups are composed of three or more loci, whereas the remaining eight groups each contained two markers. The sex-averaged map spans 365.4 cM. The marker interval of each linkage group ranges from 5.3 to 25.4 cM, and the average interval distance is 16.61 cM. The male map covers 342.7 cM, with an average intermarker distance of 15.58 cM, whereas the female map is 456.7 cM, with the average intermarker spacing of 20.76 cM. In order to screen the orthologous loci between ostrich and chicken, all of the flanking sequences of the 104 polymorphic loci, nine monomorphic loci and a further 12 reported microsatellite loci for ostrich were screened against the chicken genomic sequence using the BLAST algorithm (Altschul et al., 1990), and corresponding orthologs were found for 13 sequences. The microsatellite loci and genetic map developed in this study will be useful for QTL mapping, population genetics and phylogenetic studies in the ratite. In addition, the 13 orthologous loci identified in this study will be advantageous to the construction of a comparative genetic map between chicken and ostrich.     

Linkage maps for the Pacific abalone (genus Haliotis) based on microsatellite DNA markers

This study presents linkage maps for the Pacific abalone (Haliotis discus hannai) based on 180 microsatellite DNA markers. Linkage mapping was performed using three F1 outbred families, and a composite linkage map for each sex was generated by incorporating map information from the multiple families. A total of 160 markers are placed on the consolidated female map and 167 markers on the male map. The numbers of linkage groups in the composite female and male maps are 19 and 18, respectively; however, by aligning the two maps, 18 linkage groups are formed, which are consistent with the haploid chromosome number of H. discus hannai. The female map spans 888.1 cM (Kosambi) with an average spacing of 6.3 cM; the male map spans 702.4 cM with an average spacing of 4.7 cM. However, we encountered several linkage groups that show a high level of heterogeneity in recombination rate between families even within the same sex, which reduces the precision of the consolidated maps. Nevertheless, we suggest that the composite maps are of significant potential use as a scaffold to further extend the coverage of the H. discus hannai genome with additional markers.     

High-density Integrated Linkage Map Based on SSR Markers in Soybean

A well-saturated molecular linkage map is a prerequisite for modern plant breeding. Several genetic maps have been developed for soybean with various types of molecular markers. Simple sequence repeats (SSRs) are single-locus markers with high allelic variation and are widely applicable to different genotypes. We have now mapped 1810 SSR or sequence-tagged site markers in one or more of three recombinant inbred populations of soybean (the US cultivar ‘Jack’ × the Japanese cultivar ‘Fukuyutaka’, the Chinese cultivar ‘Peking’ × the Japanese cultivar ‘Akita’, and the Japanese cultivar ‘Misuzudaizu’ × the Chinese breeding line ‘Moshidou Gong 503’) and have aligned these markers with the 20 consensus linkage groups (LGs). The total length of the integrated linkage map was 2442.9 cM, and the average number of molecular markers was 90.5 (range of 70–114) for the 20 LGs. We examined allelic diversity for 1238 of the SSR markers among 23 soybean cultivars or lines and a wild accession. The number of alleles per locus ranged from 2 to 7, with an average of 2.8. Our high-density linkage map should facilitate ongoing and future genomic research such as analysis of quantitative trait loci and positional cloning in addition to marker-assisted selection in soybean breeding.Key words: EST-derived SSR marker, integrated linkage map, microsatellite marker, polymorphism information content     

A first linkage map of globe artichoke (Cynara cardunculus var. scolymus L.) based on AFLP, S-SAP, M-AFLP and microsatellite markers

We present the first genetic maps of globe artichoke (Cynara cardunculus var. scolymus L. 2n=2x=34), constructed with a two-way pseudo-testcross strategy. A F₁ mapping population of 94 individuals was generated between a late-maturing, non-spiny type and an early-maturing spiny type. The 30 AFLP, 13 M-AFLP and 9 S-SAP primer combinations chosen identified, respectively, 352, 38 and 41 polymorphic markers. Of 32 microsatellite primer pairs tested, 12 identified heterozygous loci in one or other parent, and 7 were fully informative as they segregated in both parents. The female parent map comprised 204 loci, spread over 18 linkage groups and spanned 1330.5 cM with a mean marker density of 6.5 cM. The equivalent figures for the male parent map were 180 loci, 17 linkage groups, 1239.4 and 6.9 cM. About 3% of the AFLP and AFLP-derived markers displayed segregation distortion with a P value below 0.01, and were not used for map construction. All the SSR loci were included in the linkage analysis, although one locus did show some segregation distortion. The presence of 78 markers in common to both maps allowed the alignment of 16 linkage groups. The maps generated provide a firm basis for the mapping of agriculturally relevant traits, which will then open the way for the application of a marker-assisted selection breeding strategy in this species.     

Genetic linkage map of the guppy,Poecilia reticulata,and quantitative trait loci analysis of male size and colour variation

We report construction of a genetic linkage map of the guppy genome using 790 single nucleotide polymorphism markers, integrated from six mapping crosses. The markers define 23 linkage groups (LGs), corresponding to the known haploid number of guppy chromosomes. The map, which spans a genetic length of 899 cM, includes 276 markers linked to expressed genes (expressed sequence tag), which have been used to derive broad syntenic relationships of guppy LGs with medaka chromosomes. This combined linkage map should facilitate the advancement of genetic studies for a wide variety of complex adaptive phenotypes relevant to natural and sexual selection in this species. We have used the linkage data to predict quantitative trait loci for a set of variable male traits including size and colour pattern. Contributing loci map to the sex LG for many of these traits.     

A genetic linkage map of Guinea yam ( Dioscorea rotundata Poir.) based on AFLP markers

A genetic linkage map of the tetraploid white yam (Dioscorea rotundata Poir.) was constructed based on 341 co-dominantly scored amplified fragment length polymorphism (AFLP) markers segregating in an intraspecific F₁ cross. The F₁ mapping population was produced by crossing a landrace cultivar TDr 93-1 as female parent to a breeding line TDr 87/00211 as the male parent. The marker segregation data were split into maternal and paternal data sets, and separate genetic linkage maps were constructed since the mapping population was an F₁ cross between two presumed heterozygous parents. The markers segregated like a diploid cross-pollinator population suggesting that the D. rotundata genome is an allo-tetraploid (2n = 4x = 40). The maternal map comprised 155 markers mapped on 12 linkage groups with a total map length of 891 cM. Three linkage groups consisted of maternal parent markers only. The paternal map consisted of 157 markers mapped on 13 linkage groups with a total map length of 852 cM. Three and one quantitative trait loci (QTLs) with effects on resistance to Yam Mosaic Virus (YMV) were identified on the maternal and paternal linkage maps, respectively. Prospects for detecting more QTLs and using marker-assisted selection in white yam breeding appear good, but this is subject to the identification of additional molecular markers to cover more of the genome.     

Genetic linkage maps of white birches (<Emphasis Type="Italic">Betula platyphylla</Emphasis> Suk. and <Emphasis Type="Italic">B. pendula</Emphasis> Roth) based on RAPD and AFLP markers

A pseudo-testcross mapping strategy was used in combination with the random amplified polymorphism DNA (RAPD) and amplified fragment length polymorphism (AFLP) genotyping methods to develop two moderately dense genetic linkage maps for Betula platyphylla Suk. (Asian white birch) and B. pendula Roth (European white birch). Eighty F₁ progenies were screened with 291 RAPD markers and 451 AFLP markers. We selected 230 RAPD and 362 AFLP markers with 1:1 segregation and used them for constructing the parent-specific linkage maps. The resultant map for B. platyphylla was composed of 226 markers in 24 linkage groups (LGs), and spanned 2864.5 cM with an average of 14.3 cM between adjacent markers. The linkage map for B. pendula was composed of 226 markers in 23 LGs, covering 2489.7 cM. The average map distance between adjacent markers was 13.1 cM. Clustering of AFLP markers was observed on several LGs. The availability of these white birch linkage maps will contribute to the molecular genetics and the implementation of marker-assisted selection in these important forest species.     

Construction of a sequence-tagged high-density genetic map of papaya for comparative structural and evolutionary genomics in brassicales

A high-density genetic map of papaya (Carica papaya L.) was constructed using microsatellite markers derived from BAC end sequences and whole-genome shot gun sequences. Fifty-four F(2) plants derived from varieties AU9 and SunUp were used for linkage mapping. A total of 707 markers, including 706 microsatellite loci and the morphological marker fruit flesh color, were mapped into nine major and three minor linkage groups. The resulting map spanned 1069.9 cM with an average distance of 1.5 cM between adjacent markers. This sequence-based microsatellite map resolved the very large linkage group 2 (LG 2) of the previous high-density map using amplified fragment length polymorphism markers. The nine major LGs of our map represent papaya's haploid nine chromosomes with LG 1 of the sex chromosome being the largest. This map validates the suppression of recombination at the male-specific region of the Y chromosome (MSY) mapped on LG 1 and at potential centromeric regions of other LGs. Segregation distortion was detected in a large region on LG 1 surrounding the MSY region due to the abortion of the YY genotype and in a region of LG6 due to an unknown cause. This high-density sequence-tagged genetic map is being used to integrate genetic and physical maps and to assign genome sequence scaffolds to papaya chromosomes. It provides a framework for comparative structural and evolutional genomic research in the order Brassicales.     

The construction of a genetic linkage map of non-heading Chinese cabbage （Brassica campestris ssp. chinensis Makino）

Non-heading Chinese cabbage （Brassica carnpestris ssp. chinensis Makino） is one of the most important vegetables in eastern China. A genetic linkage map was constructed using 127 doubled haploid （DH） lines, and the DH population was derived from a commercial hybrid ＂Hanxiao＂ （lines SW-13 x L-118）. Out of the 614 polyrnorphic markers, 43.49% were not assigned to any of the linkage groups （LGs）. Chi-square tests showed that 42.67% markers were distorted from expected Mendelian segregation ratios, and the direction of distorted segregation was mainly toward the paternal parent L-118. After sequentially removing the markers that had an interval distance smaller than 1 cM from the upper marker, the overall quality of the linkage map was increased. Two hundred and sixty-eight molecular markers were mapped into 10 LGs, which were anchored to the corresponding chromosome of the B. rapa reference map based on com- mon simple sequence repeat （SSR） markers. The map covers 973.38 cM of the genome and the average interval distance between markers was 3.63 cM. The number of markers on each LG ranged from 18 （R08） to 64 （R07）, with an average interval distance within a single LG from 1.70 cM （R07） to 6.71 cM （R06）. Among these mapped markers, 169 were sequence-related amplified polymorphism （SRAP） molecular markers, 50 were SSR markers and 49 were random amplification polymorphic DNA （RAPD） markers. With further saturation to the LG9 the current map offers a genetic tool for loci analysis for important agronomic traits.