A genetic linkage map of Pacific white shrimp (<Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>): sex-linked microsatellite markers and high recombination rates

Pacific white shrimp (Litopenaeus vannamei) is the leading species farmed in the Western Hemisphere and an economically important aquaculture species in China. In this project, a genetic linkage map was constructed using amplified fragment length polymorphism (AFLP) and microsatellite markers. One hundred and eight select AFLP primer combinations and 30 polymorphic microsatellite markers produced 2071 markers that were polymorphic in either of the parents and segregated in the progeny. Of these segregating markers, 319 were mapped to 45 linkage groups of the female framework map, covering a total of 4134.4 cM; and 267 markers were assigned to 45 linkage groups of the male map, covering a total of 3220.9 cM. High recombination rates were found in both parental maps. A sex-linked microsatellite marker was mapped on the female map with 6.6 cM to sex and a LOD of 17.8, two other microsatellite markers were also linked with both 8.6 cM to sex and LOD score of 14.3 and 16.4. The genetic maps presented here will serve as a basis for the construction of a high-resolution genetic map, quantitative trait loci (QTLs) detection, marker-assisted selection (MAS) and comparative genome mapping.     

Genetic linkage maps of two apricot cultivars ( Prunus armeniaca L.), and mapping of PPV (sharka) resistance

Genetic linkage maps for two apricot cultivars have been constructed using AFLP, RAPD, RFLP and SSR markers in 81 F1 individuals from the cross 'Goldrich' x 'Valenciano'. This family segregated for resistance to 'plum pox virus' (PPV), the most-important virus affecting Prunus species. Of the 160 RAPD arbitrary primers screened a total of 44 were selected. Sixty one polymorphic RAPD markers were scored on the mapping population: 30 heterozygous in 'Goldrich', 19 heterozygous in 'Valenciano', segregating 1:1, and 12 markers heterozygous in both parents, segregating 3:1. A total of 33 and 19 RAPD markers were mapped on the 'Goldrich' and 'Valenciano' maps respectively. Forteen primer combinations were used for AFLPs and all of them detected polymorphism. Ninety five markers segregating 1:1 were identified, of which 62 were heterozygous in the female parent 'Goldrich' and 33 in the male parent 'Valenciano'. Forty five markers were present in both parents and segregated 3:1. A total of 82 and 48 AFLP markers were mapped on the 'Goldrich' and 'Valenciano' maps. Twelve RFLPs probes were screened in the population, resulting in five loci segregating in the family, one locus heterozygous for 'Valenciano' and four heterozygous for both, segregating 1:2:1. Of the 45 SSRs screened 17 segregated in the mapping family, resulting in seven loci heterozygous for the maternal parent and ten heterozygous for both, segregating 1:2:1 or 1:1:1:1. A total of 16 and 13 co-dominant markers were mapped in the female and male parent maps respectively. A total of 132 markers were placed into eight linkage groups on the 'Goldrich' map, defining 511 cM of the total map-length. The average distance between adjacent markers was 3.9 cM. A total of 80 markers were placed into seven linkage groups on the 'Valenciano' map, defining 467.2 cM of the total map-distance, with an average interval of 5.8 cM between adjacent markers. Thirty six marker loci heterozygous in both parents revealed straightforward homologies between five linkage groups in both maps. The sharka resistance trait mapped on linkage group 2. The region containing sharka resistance is flanked by two co-dominant markers that will be used for targeted SSR development employing a recently constructed complete apricot BAC library. SSRs tightly linked to sharka resistance will facilitate MAS in breeding for resistance in apricot.     

A gene controlling sex in grapevines placed on a molecular marker-based genetic map.

Genetic maps of Vitis (2n = 38) have been constructed from an interspecific hybrid population of 58 seedlings of the cross 'Horizon' ('Seyval' x 'Schuyler') x Illinois 547-1 (V. cinerea B9 x V. rupestris B38). The maps were initially constructed based on 277 RAPD (random amplified polymorphic DNA) markers using a double-pseudotestcross strategy. Subsequently, 25 microsatellites, 4 CAPS (cleaved amplified polymorphic sequence), and 12 AFLP (amplified fragment length polymorphism) markers were added to the maps. Another 120 markers, mostly those segregating 3:1, were also assigned but not positioned on the linkage groups in the two maps. The 'Horizon' map consisted of 153 markers covering 1199 cM, with an average map distance of 7.6 cM between markers. The Illinois 547-1 map had 179 markers covering 1470 cM, with an average map distance of 8.1 cM. There were 20 linkage groups in each map, one more than the basic number of chromosomes in grapes. Ten linkage groups in each map were identified as homologous using 16 microsatellite and 2 CAPS markers polymorphic in both parents. A single locus controlling sex in grapes mapped close to a microsatellite marker. These maps provide enough coverage of the genome for QTL (quantitative trait loci) analysis and as a starting point for positional gene cloning in grapes.     

Genetic linkage map of the eastern oyster Crassostrea virginica Gmelin

Amplified fragment length polymorphisms (AFLPs), along with some microsatellite and Type I markers, were used for linkage analysis in Crassostrea virginica Gmelin, the eastern oyster. Seventeen AFLP primer combinations were selected for linkage analysis with two parents and their 81 progeny. The 17 primer combinations produced 396 polymorphic markers, and 282 of them were segregating in the two parents. Chi-square analysis indicated that 259 (91.8%) markers segregated in Mendelian ratio, while the other 23 (8.2%) showed significant (P < 0.05) segregation distortion, primarily for homozygote deficiency and probably due to deleterious recessive genes. Moderately dense linkage maps were constructed using 158 and 133 segregating markers (including a few microsatellite and Type I markers) from male and female parents, respectively. The male framework map consisted of 114 markers in 12 linkage groups, covering 647 cM. The female map had 84 markers in 12 linkage groups with a length of 904 cM. The estimated genome length was 858 cM for the male map and 1296 cM for the female map. The observed genome coverage was 84% for the male and female map when all linked markers were considered. Genetic maps observed in this study are longer than the cytogenetic map, possibly because of low marker density.     

A genetic linkage map of the sea cucumber, Apostichopus japonicus (Selenka), based on AFLP and microsatellite markers

We present the first genetic maps of the sea cucumber ( Apostichopus japonicus ), constructed with an F₁ pseudo-testcross strategy. The 37 amplified fragment length polymorphism (AFLP) primer combinations chosen identified 484 polymorphic markers. Of the 21 microsatellite primer pairs tested, 16 identified heterozygous loci in one or other parent, and six were fully informative, as they segregated in both parents. The female map comprised 163 loci, spread over 20 linkage groups (which equals the haploid chromosome number), and spanned 1522.0 cM, with a mean marker density of 9.3 cM. The equivalent figures for the male map were 162 loci, 21 linkage groups, 1276.9 and 7.9 cM. About 2.5% of the AFLP markers displayed segregation distortion and were not used for map construction. The estimated coverage of the genome was 84.8% for the female map and 83.4% for the male map. The maps generated will serve as a basis for the construction of a high-resolution genetic map and mapping of the functional genes and quantitative trait loci, which will then open the way for the application of a marker-assisted selection breeding strategy in this species.     

Genetic mapping in Eucalyptus urophylla and Eucalyptus grandis using RAPD markers.

Two single-tree linkage maps were constructed for Eucalyptus urophylla and Eucalyptus grandis, based on the segregation of 480 random amplified polymorphic DNA (RAPD) markers in a F1 interspecific progeny. A mixture of three types of single-locus segregations were observed: 244 1:1 female, 211 1:1 male, and 25 markers common to both, segregating 3:1. Markers segregating in the 1:1 ratio (testcross loci) were used to establish separate maternal and paternal maps, while markers segregating in the 3:1 ratio were used to identify homology between linkage groups of the two species maps. An average of 2.8 polymorphic loci were mapped for each arbitrary decamer primer used in the polymerase chain reaction. The mean interval size beween framework markers on the maps was 14 cM. The maps comprised 269 markers covering 1331 cM and 236 markers covering 1415 cM, in 11 linkage groups, for E. urophylla (2n = 2x = 22) and E. grandis (2n = 2x = 22), respectively. A comparative mapping analysis with two other E. urophylla and E. grandis linkage maps showed that RAPDs could be reliable markers for establishing a consensus species map. RAPD markers were automatically and quantitatively scored with an imaging analyzer. They were classified into four categories based on their optical density. A fragment intensity threshold is proposed to optimize the selection of reliable RAPD markers for future mapping experiments. Key words : genetic linkage map, Eucalyptus urophylla, Eucalyptus grandis, random amplified polymorphic DNA, RAPD, automated data collection.     

Integration genetic linkage map construction and several potential QTLs mapping of Chinese shrimp (Fenneropenaeus chinensis) based on three types of molecular markers

In this study, totally 54 selected polymorphic SSR loci of Chinese shrimp (Fenneropenaeus chinensis), in addition with the previous linkage map of AFLP and RAPD markers, were used in consolidated linkage maps that composed of SSR, AFLP and RAPD markers of female and male construction, respectively. The female linkage map contained 236 segregating markers, which were linked in 44 linkage groups, and the genome coverage was 63.98%. The male linkage map contained 255 segregating markers, which were linked in 50 linkage groups, covering 63.40% of F. chinensis genome. There were nine economically important traits and phenotype characters of F. chinensis were involved in QTL mapping using multiple-QTL mapping strategy. Five potential QTLs associated with standard length (q-standardl-01), with cephalothorax length (q-cephal-01), with cephaloghorax width (q-cephaw-01), with the first segment length (q-firsel-01) and with anti-WSSV (q-antiWSSV-01) were detected on female LG1 and male LG44 respectively with LOD> 2.5. The QTL q-firsel-01 was at 73.603 cM of female LG1. Q-antiWSSV-01 was at 0 cM of male LG44. The variance explained of these five QTLs was from 19.7-33.5% and additive value was from -15.9175 to 7.3675. The closest markers to these QTL were all SSR, which suggested SSR marker was superior to AFLP and RAPD in the QTL mapping.     

Construction of a genetic linkage map in <Emphasis Type="Italic">Fenneropenaeus chinensis</Emphasis> (Osbeck) using RAPD and SSR markers

The primary genetic linkage maps of Fenneropenaeus chinensis (Osbeck) were constructed by using the “two-way pseudo-testcross” strategy with RAPD and SSR markers. Parents and F1 progeny were used as segregating populations. Sixty-one RAPD primers and 20 pairs of SSR primers were screened from 460 RAPD primers and 44 pairs of SSR primers. These primers were used to analyze the parents and 82 progeny of the mapping family. About 146 primers (128 RAPDs, 18 microsatellites) in the female and 127 primers (109 RAPDs, 18 microsatellites) in the male were segregating markers. The female linkage map included eight linkage groups, nine triplets and 14 doublets, spanning 1,173 cM with the average marker density of 11.28 cM, and the observed coverage was 59.36%. The male linkage map included 10 linkage groups, 12 triplets and seven doublets, spanning 1,144.6 cM with the average marker density of 12.05 cM, and the observed coverage was 62.01%. The construction of the F. chinensis genetic linkage maps here opened a new prospect for marker-assisted selection program, comparative genomics and quantitative trait loci (QTL) gene location and cloning.     

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.     

AFLP-based genetic linkage map for the red flour beetle (Tribolium castaneum)

The red flour beetle (Tribolium castaneum) is a major pest of stored grain and grain products and a popular model species for a variety of ecological, evolutionary, and developmental biology studies. Development of a linkage map based on reproducible and highly polymorphic molecular markers would greatly facilitate research in these disciplines. We have developed a genetic linkage map using 269 amplified fragment length polymorphism (AFLP) markers. Ten previously known random amplified polymorphic DNA (RAPD) markers were used as anchor markers for linkage group assignment. The linkage map was constructed through genotyping two independent F(2) segregating populations with 48 AFLP primer combinations. Each primer combination generated an average of 4.6 AFLP markers eligible for linkage mapping. The length of the integrated map is 573 cM, giving an average marker resolution of 2.0 cM and an average physical distance per genetic distance of 350 kb/cM. A cluster of loci on linkage group 3 exhibited significant segregation distortion. We have also identified six X-linked and two Y-linked markers. Five mapped AFLP fragments were sequenced and converted to sequence-tagged site (STS) markers.     

Preliminary Study on Linkage Mapping Based on Microsatellite DNA and AFLP Markers Using Homozygous Clonal Fish in Ayu (<Emphasis Type="Italic">Plecoglossus altivelis</Emphasis>)

A mapping referential family (F₁) of ayu was produced by crossing a normal diploid male with a homozygous clonal female. A genetic linkage map was constructed using 191 amplified fragment length polymorphism (AFLP) and 4 microsatellite DNA markers. A total of 178 loci were mapped in 36 linkage groups comprising 1659.6 cM, which includes approximately 77.3% to 81.8% of the total genome. As the markers were randomly distributed over the genome, they showed high efficiency for the construction of a wide linkage map.     

Integration genetic linkage map construction and several potential QTLs mapping of Chinese shrimp (<Emphasis Type="Italic">Fenneropenaeus chinensis</Emphasis>) based on three types of molecular markers

In this study, totally 54 selected polymorphic SSR loci of Chinese shrimp (Fenneropenaeus chinensis), in addition with the previous linkage map of AFLP and RAPD markers, were used in consolidated linkage maps that composed of SSR, AFLP and RAPD markers of female and male construction, respectively. The female linkage map contained 236 segregating markers, which were linked in 44 linkage groups, and the genome coverage was 63.98%. The male linkage map contained 255 segregating markers, which were linked in 50 linkage groups, covering 63.40% of F. chinensis genome. There were nine economically important traits and phenotype characters of F. chinensis were involved in QTL mapping using multiple-QTL mapping strategy. Five potential QTLs associated with standard length (q-standardl-01), with cephalothorax length (q-cephal-01), with cephaloghorax width (q-cephaw-01), with the first segment length (q-firsel-01) and with anti-WSSV (q-antiWSSV-01) were detected on female LG1 and male LG44 respectively with LOD > 2.5. The QTL q-firsel-01 was at 73.603 cM of female LG1. Q-antiWSSV-01 was at 0 cM of male LG44. The variance explained of these five QTLs was from 19.7–33.5% and additive value was from −15.9175 to 7.3675. The closest markers to these QTL were all SSR, which suggested SSR marker was superior to AFLP and RAPD in the QTL mapping.     

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.     

A microsatellite linkage map of the blacklip abalone, Haliotis rubra

There is considerable scope for genetic improvement of cultured blacklip abalone Haliotis rubra in Australia using molecular marker-assisted, selective-breeding practices. Such improvement is dependent on the availability of primary genetic resources, such as a genetic linkage map. This study presents a first-generation linkage map of H. rubra, containing 122 microsatellite markers typed in a single full-sib family. These loci mapped to 17 and 20 linkage groups for the male and female respectively, and when aligned, the consensus map represented 18 linkage groups. The male linkage map contained 102 markers (one unlinked) covering 621 cM with an average intermarker spacing of 7.3 cM, and the female map contained 98 markers (eight unlinked) covering 766 cM with an average intermarker spacing of 9.8 cM. Analysis of markers informative in both parents showed a significantly higher recombination rate in the female parent, with an average male-to-female recombination ratio of 1:1.45 between linked pairs of markers. This linkage map represents a significant advancement in the genetic resource available for H. rubra and provides a framework for future quantitative trait loci mapping and eventual implementation of marker-assisted selection.     

Genetic Mapping of Laminaria japonica and L. Iongissima Using Amplified Fragment Length Polymorphism Markers in a ＂Two-Way Pseudo- Testcross＂ Strategy

With a ＂two-way pseudo-testcross＂ mapping strategy, we applied the amplified fragment length polymorphism （AFLP） markers to construct two moderate density genetic linkage maps for Laminaria. The linkage maps were generated from the 60 progenies of the F1 cross family （Laminaria iongissima Aresch. × L. Japonica Miyabe） with twenty pairs of primer combinations. Of the 333 polymorphic loci scored in 60 progenies, 173 segregated in a 1：1 ratio, corresponding to DNA polymorphisms heterozygous in a single parent, and the other 58 loci existing in both parents followed a 3：1 Mendelian segregation ratio. Among the loci with 1：1 segregating ratios, 79 loci were ordered in 14 linkage groups （648.6 cM） of the paternal map, and 72 loci were ordered in 14 linkage groups （601.9 cM） of the maternal map. The average density of loci was approximately 1 per 8 cM. To Investigate the homologies between two parental maps, we used 58 loci segregated 3：1 for further analysis, and deduced one homologous linkage group. The linkage data developed in these maps will be useful for detecting loci-controlling commercially important traits for Laminaria.     

A genetic linkage map for Pinus radiata based on RFLP, RAPD, and microsatellite markers

A genetic linkage map for radiata pine (Pinus radiata D. Don) has been constructed using segregation data from a three-generation outbred pedigree. A total of 208 loci were analyzed including 165 restriction fragment length polymorphism (RFLP), 41 random amplified polymorphic DNA (RAPD) and 2 microsatellite markers. The markers were assembled into 22 linkage groups of 2 or more loci and covered a total distance of 1382 cM. Thirteen loci were unlinked to any other marker. Of the RFLP loci that were mapped, 93 were detected by loblolly pine (P. taeda L.) cDNA probes that had been previously mapped or evaluated in that species. The remaining 72 RFLP loci were detected by radiata pine probes from a PstI genomic DNA library. Two hundred and eighty RAPD primers were evaluated, and 41 loci which were segregating in a 11 ratio were mapped. Two microsatellite markers were also placed on the map. This map and the markers derived from it will have wide applicability to genetic studies in P. radiata and other pine species.     

Linkage map of Japanese black pine based on AFLP and RAPD markers including markers linked to resistance against the pine needle gall midge

Macrogametophytes derived from the seeds of a tree resistant to pine needle gall midge (PGM) were analyzed using amplified fragment length polymorphism (AFLP). A total of 244 segregating loci were detected among 71 macrogametophytes. Combining the AFLP results with previously reported segregation data for 127 random amplified polymorphic DNA (RAPD) markers, 157 AFLP and 50 RAPD markers with confirmed map positions were assigned to 20 linkage groups and three pairs covering 2085.5 cM with an average distance of 10.1 cM. The total map distance covers about 77.1–78.4% of the total genome, estimated to be approximately 2665–2719 cM in length. Thus, using AFLP markers, the previous RAPD map of this tree was improved in terms of the average distance between markers, the total map distance, and coverage of the genome. Three RAPD markers linked to a gene associated with resistance to PGM were also located on this map. Rceived: 14 April 2000 / Accepted: 21 August 2000     

A first linkage map of olive (Olea europaea L.) cultivars using RAPD,AFLP, RFLP and SSR markers

The first linkage map of the olive (Olea europaea L.) genome has been constructed using random amplified polymorphic DNA (RAPD) and amplified fragment length polymorphisms (AFLP) as dominant markers and a few restriction fragment length polymorphisms (RFLP) and simple-sequence repeats (SSR) as codominant markers. Ninety-five individuals of a cross progeny derived from two highly heterozygous olive cultivars, Leccino and Dolce Agogia, were used by applying the pseudo test-cross strategy. From 61 RAPD primers 279 markers were obtained - 158 were scored for Leccino and 121 for Dolce Agogia. Twenty-one AFLP primer combinations gave 304 useful markers - 160 heterozygous in Leccino and 144 heterozygous in Dolce Agogia. In the Leccino map 249 markers (110 RAPD, 127 AFLP, 8 RFLP and 3 SSR) were linked. This resulted in 22 major linkage groups and 17 minor groups with fewer than four markers. In the Dolce Agogia map, 236 markers (93 RAPD, 133 AFLP, 6 RFLP and 4 SSR) were linked; 27 major linkage groups and three minor groups were obtained. Codominant RFLPs and SSRs, as well as few RAPDs in heteroduplex configuration, were used to establish homologies between linkage groups of both parents. The total distance covered was 2,765 cM and 2,445 cM in the Leccino and Dolce Agogia maps, respectively. The mean map distance between adjacent markers was 13.2 cM in Leccino and 11.9 cM in Dolce Agogia, respectively. Both AFLP and RAPD markers were homogeneously distributed in all of the linkage groups reported. The stearoyl-ACP desaturase gene was mapped on linkage group 4 of cv. Leccino.     

AFLP-Based Genetic Linkage Maps of the Pacific Oyster <Emphasis Type="Italic">Crassostrea gigas</Emphasis> Thunberg

Amplified fragment length polymorphisms (AFLPs) were used for genome mapping in the Pacific oyster Crassostrea gigas Thunberg. Seventeen selected primer combinations produced 1106 peaks, of which 384 (34.7%) were polymorphic in a backcross family. Among the polymorphic markers, 349 were segregating through either the female or the male parent. Chi-square analysis indicated that 255 (73.1%) of the markers segregated in a Mendelian ratio, and 94 (26.9%) showed significant (P < 0.05) segregation distortion. Separate genetic linkage maps were constructed for the female and male parents. The female framework map consisted of 119 markers in 11 linkage groups, spanning 1030.7 cM, with an average interval of 9.5 cM per marker. The male map contained 96 markers in 10 linkage groups, covering 758.4 cM, with 8.8 cM per marker. The estimated genome length of the Pacific oyster was 1258 cM for the female and 933 cM for the male, and the observed coverage was 82.0% for the female map and 81.3% for the male map. Most distorted markers were deficient for homozygotes and closely linked to each other on the genetic map, suggesting the presence of major recessive deleterious genes in the Pacific oyster.     

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.