Identification and mapping on chromosome 9 of RAPD markers linked to Sw-5 in tomato by bulked segregant analysis

Bulked segregant analysis was used to identify random amplified polymorphic DNA (RAPD) markers linked to the Sw-5 gene for resistance to tomato spotted wilt virus (TSWV) in tomato. Using two pools of phenotyped individuals from one segregating population, we identified four RAPD markers linked to the gene of interest. Two of these appeared tightly linked to Sw-5, whereas another, linked in repulsion phase, enabled the identification of heterozygous and susceptible plants. After linkage analysis of an F₂ population, the RAPD markers were shown to be linked to Sw-5 within a distance of 10.5 cM. One of the RAPD markers close to Sw-5 was used to develop a SCAR (sequence characterized amplified region) marker. Another RAPD marker was stabilized into a pseudo-SCAR marker by enhancing the specificity of its primer sequence without cloning and sequencing. RAPD markers were mapped to chromosome 9 on the RFLP tomato map developed by Tanksley et al. (1992). The analysis of 13 F₃ families and eight BC₂ populations segregating for resistance to TSWV confirmed the linkage of the RAPD markers found. These markers are presently being used in marker-assisted plant breeding.     

Development of RAPD and SCAR markers linked to the Russian wheat aphid resistance gene Dn2 in wheat

 RAPD (random amplified polymorphic DNA) analysis was used to identify molecular markers linked to the Dn2 gene conferring resistance to the Russian wheat aphid (Diuraphis noxia Mordvilko). A set of near-isogenic lines (NILs) was screened with 300 RAPD primers for polymorphisms linked to the Dn2 gene. A total of 2700 RAPD loci were screened for linkage to the resistance locus. Four polymorphic RAPD fragments, two in coupling phase and two in repulsion phase, were identified as putative RAPD markers for the Dn2 gene. Segregation analysis of these markers in an F₂ population segregating for the resistance gene revealed that all four markers were closely linked to the Dn2 locus. Linkage distances ranged from 3.3 cM to 4.4 cM. Southern analysis of the RAPD products using the cloned RAPD markers as probes confirmed the homology of the RAPD amplification products. The coupling-phase marker OPB10_880c and the repulsion-phase marker OPN1_400r were converted to sequence characterized amplified region (SCAR) markers. SCAR analysis of the F₂ population and other resistant and susceptible South African wheat cultivars corroborated the observed linkage of the RAPD markers to the Dn2 resistance locus. These markers will be useful for marker-assisted selection of the Dn2 gene for resistance breeding and gene pyramiding. Received: 1 July 1997 / Accepted: 20 October 1997     

Utility of RAPD markers in identifying genetic linkages to genes of economic interest in peach

The identification of molecular markers linked to economically important traits for use in crop improvement is very important in long-lived perennial species. Three-hundred-and-sixty RAPD primers were used with bulked segregant analysis to identify markers linked to loci of specific interest in peach [(Prunus persica) L. Batch] and peach x almond [(Prunus dulcis) Batch] crosses. The traits analyzed included flesh color, adhesion, and texture; pollen fertility; plant stature; and three isozyme loci. The Mendelian behavior of the RAPD loci was established, and RAPD markers were mapped relative to the loci controlling flesh color, adhesion, and texture, and the isozyme loci Mdh-1, 6Pgd-2 and Aat-1, as well as the existing RFLP genetic linkage map constructed previously using a peach x almond F₂ population. This technique has facilitated rapid identification of RAPD and RFLP markers that are linked to the traits under study. Loci controlling these traits mapped predominantly to linkage groups 2 and 3 of the peach genetic linkage map. Linkages to genes with both dominant and co-dominant alleles were identified, but linkages to dominant genes were more difficult to find. In several crosses, RAPD marker bands proved to be allelic. One co-dominant RAPD formed a heteroduplex band in heterozygous individuals and in mixtures of alternate homozygotes. The Mendelian behavior of the RAPD loci studied was established and the results suggest that RAPD markers will be useful for plant improvement in peach.     

Identification of SCAR marker linking to longer frond length of <Emphasis Type="Italic">Saccharina japonica</Emphasis> (Laminariales,Phaeophyta) using bulked-segregant analysis

To construct a molecular-marker-assisted selection (MAS) system, research was done on identifying molecular markers linking to longer frond length, a crucial selection index in the breeding of the commercially important seaweed Saccharina japonica. An F₂-segregant population of 92 individuals was obtained by crossing two prominent S. japonica strains. Genomic DNA from ten individuals with the longest frond and ten individuals with the shortest frond in the F₂-segregant population were mixed to create two DNA pools for screening polymorphic markers. In bulked-segregant analysis (BSA), out of 100 random amplified polymorphic DNA (RAPD) primers only two produced three polymorphic RAPD markers between the two DNA pools. In conversion of the three RAPD markers into sequence-characterized amplified region (SCAR) markers, only one was successfully converted into a SCAR marker FL-569 linking to the trait of longer frond. Test of the marker FL-569 showed that 80% of the individuals with longest fronds in a wild population and 87.5% of individuals with the longest fronds in an inbred line “Zhongke No. 2” could be detected by FL-569. Additionally, genetic linkage analysis showed that the SCAR marker could be integrated into the reported genetic map and QTL mapping showed that FL-569 linking to qL1-1. The obtained marker FL-569 will be beneficial to MAS in S. japonica breeding.     

Evaluation of inter-simple sequence repeat analysis for mapping in Citrus and extension of the genetic linkage map

Inter-simple sequence repeat (ISSR) analysis was evaluated for its usefulness in generating markers to extend the genetic linkage map of Citrus using a backcross population previously mapped with restriction fragment length polymorphism (RFLP), random amplified polymorphic DNA (RAPD) and isozyme markers. ISSR markers were obtained through the simple technique of PCR followed by analysis on agarose gels, using simple sequence repeat (SSR) primers. Optimization of reaction conditions was achieved for 50% of the SSR primers screened, and the primers amplified reproducible polymorphic bands in the parents and progeny of the backcross population. Mendelian segregation of the polymorphic bands was demonstrated, with an insignificant number of skewed loci. Most of the SSR primers produced dominant loci; however co-dominance was observed with loci derived from three primers. A new genetic map was produced by combining the segregation data for the ISSR markers and data for the RFLP, RAPD and isozyme markers from the previous map and creating genetic linkages among all the markers using JoinMap 2.0 mapping software. The new map has an improved distribution of markers along the linkage groups with fewer gaps, and marker order showed partial or complete conservation in the linkage groups. The incorporation of ISSR markers into the genetic linkage map demonstrates that ISSR markers are suitable for genetic mapping in Citrus. Received: 3 February 2000 / Accepted: 12 May 2000     

A Preliminary Linkage Map of the Tick, Ixodes scapularis

A linkage map of the Ixodes scapularis genome was constructed based upon segregation amongst 127 loci. These included 84 random amplified polymorphic DNA (RAPD) markers, 32 Sequence-Tagged RAPD (STAR) markers, 5 cDNAs, and 5 microsatellites in 232 F₁ intercross progeny from a single, field-collected P₁ female. A preliminary linkage map of 616 cM was generated across 14 linkage groups with one marker every 10.8 cM. Assuming a genome size of ∼10⁹ bp, the relationship of physical to genetic distance is ∼300 kb/cM in the I. scapularis genome. This revised version was published online in July 2006 with corrections to the Cover Date.     

A linkage map of chickpea (Cicer arietinum L.) based on populations from Kabuli × Desi crosses: location of genes for resistance to fusarium wilt race 0

Two recombinant inbred line (RIL) populations derived from intraspecific crosses with a common parental line (JG62) were employed to develop a chickpea genetic map. Molecular markers, flower colour, double podding, seed coat thickness and resistance to fusarium wilt race 0 (FOC-0) were included in the study. Joint segregation analysis involved a total of 160 markers and 159 RILs. Ten linkage groups (LGs) were obtained that included morphological markers and 134 molecular markers (3 ISSRs, 13 STMSs and 118 RAPDs). Flower colour (B/b) and seed coat thickness (Tt/tt) appeared to be linked to STMS (GAA47). The single-/double-podding locus was located on LG9 jointly with two RAPD markers and STMS TA80. LG3 included a gene for resistance to FOC-0 (Foc0₁/foc0₁) flanked by RAPD marker OPJ20₆₀₀ and STMS marker TR59. The association of this LG with FOC-0 resistance was confirmed by QTL analysis in the CA2139 × JG62 RIL population where two genes were involved in the resistance reaction. The STMS markers enabled comparison of LGs with preceding maps.     

Identification and mapping of resistance gene analogs and a white rust resistance locus in<Emphasis Type="Italic"> Brassica rapa</Emphasis> ssp.<Emphasis Type="Italic"> oleifera</Emphasis>

The objective of this investigation was to tag a locus for white rust resistance in a Brassica rapa ssp. oleifera F₂ population segregating for this trait, using bulked segregant analysis with random amplified polymorphic DNA (RAPD) markers, linkage mapping and a candidate gene approach based on resistance gene analogs (RGAs). The resistance source was the Finnish line Bor4109. The reaction against white rust races 7a and 7v was scored in 20 seedlings from each self-pollinated F₂ individual. The proportion of resistant plants among these F₃ families varied from 0 to 67%. Bulked segregant analysis did not reveal any markers linked with resistance and, therefore, a linkage map with 81 markers was created. A locus that accounted for 18.4% of the variation in resistance to white rust was mapped to linkage group (LG) 2 near the RAPD marker Z19a. During the study, a bacterial resistance gene homologous to Arabidopsis RPS2 and six different RGAs were sequenced. RPS2 and five of the RGAs were mapped to linkage groups LG1, LG4 and LG9. Unfortunately, none of the RGAs could be shown to be associated with white rust resistance.Communicated by H.C. BeckerThe nucleotide sequence data reported has been deposited in the Genbank under the accession numbers AF315081–AF315087.     

Construction of genetic linkage map of the medicinal and ornamental plant <Emphasis Type="Italic">Catharanthus roseus</Emphasis>

An integrated genetic linkage map of the medicinal and ornamental plant Catharanthus roseus, based on different types of molecular and morphological markers was constructed, using a F₂ population of 144 plants. The map defines 14 linkage groups (LGs) and consists of 131 marker loci, including 125 molecular DNA markers (76 RAPD, 3 RAPD combinations; 7 ISSR; 2 EST-SSR from Medicago truncatula and 37 other PCR based DNA markers), selected from a total of 472 primers or primer pairs, and six morphological markers (stem pigmentation, leaf lamina pigmentation and shape, leaf petiole and pod size, and petal colour). The total map length is 1131.9 cM (centiMorgans), giving an average map length and distance between two markers equal to 80.9 cM and 8.6 cM, respectively. The morphological markers/genes were found linked with nearest molecular or morphological markers at distances varying from 0.7 to 11.4 cM. Linkage was observed between the morphological markers concerned with lamina shape and petiole size of leaf on LG1 and leaf, stem and petiole pigmentation and pod size on LG8. This is the first genetic linkage map of C. roseus.     

Genetic linkage map of ISSR and RAPD markers in Einkorn wheat in relation to that of RFLP markers

 The potential of PCR-based markers for construction of a genetic linkage map in Einkorn wheat was investigated. From a comparison of polymorphisms between two Einkorn wheats, Triticum monococcum (Mn) and T. boeoticum (Bt), we obtained 49 polymorphic bands produced by 33 primers for inter-simple sequence repeat (ISSR) and 36 polymorphic bands shown by 25 combinations of random amplified polymorphic DNA (RAPD) primers for mapping in 66 individuals in the F₂ population. Although 44 ISSR fragments and 29 RAPD fragments statistically showed a 3 : 1 segregation ratio in the F₂ population, only 9 markers each of the ISSR and RAPD bands were able to be mapped on the RFLP linkage map of Einkorn wheat. ISSR markers were distributed throughout the chromosomes. The mapped positions of the ISSR markers seemed to be similar to those obtained by the RFLP markers. On the other hand, 4 of the 9 RAPD markers could map the RFLP marker-poor region on the short arm of 3A^m, suggesting a potential to map novel regions containing repetitive sequences. Comparisons of the genetic linkage map of Einkorn wheat to the linkage map and cytological map of common wheat revealed that the marker orders between the two maps of Einkorn wheat and common wheat coincided except for 4A, which harbors chromosome rearrangements specific for polyploid wheats, indicating a conservatism between the two genomes. Recombinations in Einkorn wheat chromosomes took place more frequently around the centromere and less at the distal part of chromosomes in comparison to those in common wheat. Nevertheless, recombinations even in Einkorn wheat chromosomes were strongly suppressed around the centromere. In fact, the markers located within 1 cM of the centromere were located almost in the central part of the chromosome arm. Received: 7 June 1997 / Accepted: 17 June 1997     

Genetic analysis and molecular mapping of maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) stalk rot resistant gene<Emphasis Type="Italic"> Rfg</Emphasis>1

One single pathogen Fusarium graminearum Schw. was inoculated to maize inbred lines 1,145 (Resistant) and Y331 (Susceptive), and their progenies of F₁, F₂ and BC₁F₁ populations. Field statistical data revealed that all of the F₁ individuals were resistant to the disease and that the ratio of resistant plants to susceptive plants was 3:1 in the F₂ population, and 1:1 in the BC₁F₁ population. The results revealed that a single dominant gene controls the resistance to F. graminearum Schw.. The resistant gene to F. graminearum Schw. was denominated as Rfg1 according to the standard principle of the nomenclature of the plant disease resistant genes. RAPD (randomly amplified polymorphic DNA) combined with BSA (bulked segregant analysis) analysis was carried out in the developed F₂ and BC₁F₁ populations, respectively. Three RAPD products screened from the RAPD analysis with 820 Operon 10-mer primers showed the linkage relation with the resistant gene Rfg1. The three RAPD amplification products (OPD-20₁₀₀₀, OPA-04₁₁₀₀ and OPY-04₉₀₀) were cloned and their copy numbers were determined. The results indicated that only OPY-04₉₀₀ was a single-copy sequence. Then, OPY-04₉₀₀ was used as a probe to map the Rfg1 gene with a RIL F₇ mapping population provided by Henry Nguyen, which was developed from the cross S3×Mo17. Rfg1 was primarily mapped on chromosome 6 between the two linked markers OPY-04₉₀₀ and umc21 (Bin 6.04–6.05). In order to confirm the primary mapping result, 25 SSR (simple sequence repeat) markers and six RFLP (restriction fragment length polymorphism) markers in the Rfg1 gene-encompassing region were selected, and their linkage relation with Rfg1 was analyzed in our F₂ population. Results indicated that SSR marker mmc0241 and RFLP marker bnl3.03 are flanking the Rfg1 gene with a genetic distance of 3.0 cM and 2.0 cM, respectively. This is the first time to name and to map a single resistant gene of maize stalk rot through a single pathogen inoculation and molecular marker analysis.Communicated by H.F. Linskens     

Identification of RAPD markers linked to the gene PM 1 for resistance to powdery mildew in wheat

 Powdery mildew caused by Blumeria graminis DC. f. sp. triticiém. Marchal is an important disease of wheat (Triticum aestivum L. em Thell). We report here the identification of three random amplified polymorphic DNA (RAPD) markers closely linked to a gene for resistance to B. graminis in wheat. RAPD-PCR (polymerase chain reaction) analysis was conducted using bulked segregant analysis of closely related lines developed from a segregating F₅ family. The F₅ family was derived from a cross between the susceptible cultivar Clark and the resistant line Zhengzhou 871124. Genetic analysis indicated that resistance of Zhengzhou 871124 to powdery mildew is conferred by the gene Pm1. After performing RAPD-PCR analysis with 1300 arbitrary 10-mer primers and agarose-gel electrophoresis, two RAPD markers, UBC320₄₂₀ and UBC638₅₅₀, were identified to be co-segregating with the disease resistance. No recombinants were observed between either of the RAPD markers and the gene for resistance to powdery mildew after analysis of 244 F₂ plants. The third RAPD marker, OPF12₆₅₀, was identified with denaturing gradient-gel electrophoresis (DGGE), and was determined to be 5.4±1.9 cM from the resistance gene. UBC320₄₂₀ and UBC638₅₅₀ were present in wheat powdery mildew differential lines carrying the gene Pm1, suggesting linkage between these markers and the Pm1 resistance gene. Co-segregation between Pm1 and the two markers UBC320₄₂₀ and UBC638₅₅₀ was confirmed in a segregating population derived from a cross with CI14114, the wheat differential line carrying Pm1. The method of deriving closely related lines from inbred families that are segregating for a trait of interest should find wide application in the identification of DNA markers linked to important plant genes. The RAPD marker UBC638₅₅₀ was converted to a sequence tagged site (STS). RAPD markers tightly linked to target genes may facilitate selection and enable gene pyramiding for powdery mildew resistance in wheat breeding programs. Received: 10 December 1995 / Accepted: 13 September 1996     

A genetic linkage map of lentil (Lens sp.) based on RAPD and AFLP markers using recombinant inbred lines

 A genetic linkage map of Lens sp. was constructed with 177 markers (89 RAPD, 79 AFLP, six RFLP and three morphological markers) using 86 recombinant inbred lines (F_6:8) obtained from a partially interspecific cross. The map covered 1073 cM of the lentil genome with an average distance of 6.0 cM between adjacent markers. Previously mapped RFLP markers were used as anchor probes. The morphological markers, pod indehiscence, seed-coat pattern and flower-color loci were mapped. Out of the total linked loci, 8.4% showed segregation distortion. More than one-fourth of the distorted loci were clustered in one linkage group. AFLP markers showed more segregation distortion than the RAPD markers. The AFLP and RAPD markers were intermingled and clustering of AFLPs was seldom observed. This is the most extensive genetic linkage map of lentil to-date. The marker density of this map could be used for the identification of markers linked to quantitative trait loci in this population. Received: 6 November 1997 / Accepted: 10 February 1998     

Molecular mapping of the Oregon Wolfe Barleys: a phenotypically polymorphic doubled-haploid population

A phenotypically polymorphic barley (Hordeum vulgare L.) mapping population was developed using morphological marker stocks as parents. Ninety-four doubled-haploid lines were derived for genetic mapping from an F₁ using the Hordeum bulbosum system. A linkage map was constructed using 12 morphological markers, 87 restriction fragment length polymorphism (RFLP), five random amplified polymorphic DNA (RAPD), one sequence-tagged site (STS), one intron fragment length polymorphism (IFLP), 33 simple sequence repeat (SSR), and 586 amplified fragment length polymorphism (AFLP) markers. The genetic map spanned 1,387 cM with an average density of one marker every 1.9 cM. AFLP markers tended to cluster on centromeric regions and were more abundant on chromosome 1 (7H). RAPD markers showed a high level of segregation distortion, 54% compared with the 26% observed for AFLP markers, 27% for SSR markers, and 18% for RFLP markers. Three major regions of segregation distortion, based on RFLP and morphological markers, were located on chromosomes 2 (2H), 3 (3H), and 7 (5H). Segregation distortion may indicate that preferential gametic selection occurred during the development of the doubled-haploid lines. This may be due to the extreme phenotypes determined by alleles at morphological trait loci of the dominant and recessive parental stocks. Several molecular markers were found to be closely linked to morphological loci. The linkage map reported herein will be useful in integrating data on quantitative traits with morphological variants and should aid in map-based cloning of genes controlling morphological traits. Received: 23 August 2000 / Accepted: 15 December 2000     

Identification and Mapping of chi115 Gene and DNA Markers Linked to It in Pea (Pisum sativum L.)

Chlorophyll mutant Chi115 was induced by ethylmethane sulfonate (EMS) treatment of seeds of genotype Torsdag in Moscow State University and is characterized by lighter plant color. The monogenic nature of the mutant was determined by analyzing the F₂ population from a cross between two P. sativum genotypes, WL1238 and Chi115. To establish a local map around the chi115gene, the RAPD and ISSR techniques were used with 45 RAPD and 10 ISSR primers in combination with bulked segregant analysis (BSA). Linkage of 12 RAPDs and 2 ISSRs to the chi115locus was observed in analysis of F₂ single plants. Two RAPD markers that were closely associated with the chi115 gene were converted into the sequence characterized amplified region (SCAR) markers. By lowering the LOD score to 2, the linkage group containing the chi115 gene could be linked to the b gene (color of the flower) on linkage group III. Nevertheless, to prove the result obtained, three CAPS markers Sodmt, TubA1, and Rb were chosen on linkage group III. The results of linkage analysis showed that these CAPS markers were located within the linkage group including thechi115gene.     

Characterization and fine mapping of <Emphasis Type="Italic">RppQ</Emphasis>, a resistance gene to southern corn rust in maize

Southern corn rust (SCR) is a fungal disease caused by Puccinia polysora Underw, which can infect maize and may result in substantial yield losses in maize production. The maize inbred line Qi319 carries the SCR resistance gene RppQ. In order to identify molecular markers linked to the RppQ gene, several techniques were utilized including random amplified polymorphic DNA (RAPD), simple sequence repeat (SSR), and amplified fragment length polymorphism (AFLP). In addition, sequence characterized amplified region (SCAR) techniques combined with bulked segregant analysis (BSA) were used. Seven RAPD markers, eight SSR markers, and sixty-three AFLP primer combinations amplified polymorphisms between two parents and two bulk populations. A large F₂ population was used for genetic analysis and for fine mapping of the RppQ gene region. One AFLP polymorphic band, M-CAA/E-AGC₃₂₄, was converted to a SCAR marker, MA7, which was mapped to a position 0.46 cM from RppQ. Finally, the RppQ gene was mapped between the SCAR marker MA7 and the AFLP marker M-CCG/E-AGA₁₅₇ with distances of 0.46 and 1.71 cM, respectively.     

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.     

An intersubspecific genetic map of<Emphasis Type="Italic"> Lens</Emphasis>

A Lens map was developed based on the segregational analysis of five kinds of molecular and morphological genetic markers in 113 F₂ plants obtained from a single hybrid of Lens culinaris ssp. culinaris × L. c. ssp. orientalis. A total of 200 markers were used on the F₂ population, including 71 RAPDs, 39 ISSRs, 83 AFLPs, two SSRs and five morphological loci. The AFLP technique generated more polymorphic markers than any of the others, although AFLP markers also showed the highest proportion (29.1%) of distorted segregation. At a LOD score of 3.0, 161 markers were grouped into ten linkage groups covering 2,172.4 cM, with an average distance between markers of 15.87 cM. There were six large groups with 12 or more markers each, and four small groups with two or three markers each. Thirty-nine markers were unlinked. A tendency for markers to cluster in the central regions of large linkage groups was observed. Likewise, clusters of AFLP, ISSR or RAPD markers were also observed in some linkage groups, although RAPD markers were more evenly spaced along the linkage groups. In addition, two SSR, three RAPD and one ISSR markers segregated as codominant. ISSR markers are valuable tools for Lens genetic mapping and they have a high potential in the generation of saturated Lens maps.Communicated by H.C. Becker     

A genetic map of Maritime pine based on AFLP, RAPD and protein markers

TheAFLP (amplified fragment length polymorphism) technique was adapted to carry out genetic analysis in maritime pine, a species characterized by a large genome size (24 pg/C). A genetic linkage map was constructed for one F₁ individual based on 239 AFLP and 127 RAPD (randomly amplified polymorphic DNA) markers. Markers were scored on megagametophytes (1n) from 200 germinated F₂ seedlings. Polymorphism rate, labour time and cost of both AFLP and RAPD techniques were compared. The AFLP technique was found to be twice as fast and three-times less costly per marker than the RAPD technique. Thirteen linkage groups were identified with a LOD score ≥6 covering 1873 cM, which provided 93.4% of genome coverage. Proteins were extracted from needles (2n) of the F₂ progeny and revealed by 2-DE (two-dimensional electrophoresis). Thirty one segregating proteins were mapped using a QTL detection strategy based on the quantification of protein accumulation. Two framework maps of the same F₁ individual are now available. The first map (Plomion et al. 1996) uses RAPD markers and the second map, presented in this study, uses mostly AFLP markers. Although the total genetic length of both maps was almost identical, differences among homologous groups were observed. Received: 11 February 1999 / Accepted: 29 April 1999     

A consensus map for <Emphasis Type="Italic">Cucurbita pepo</Emphasis>

Using random amplified polymorphic DNA (RAPD), amplified fragment length polymorphism (AFLP), simple sequence repeats (SSR), and morphological traits, the first genetic maps for Cucurbita pepo (2n=2x=40) were constructed and compared. The two mapping populations consisted of 92 F₂ individuals each. One map was developed from a cross between an oil-seed pumpkin breeding line and a zucchini accession, into which genes for resistance to Zucchini Yellow Mosaic Virus (ZYMV) from a related species, C. moschata, had been introgressed. The other map was developed from a cross between an oil-seed pumpkin and a crookneck variety. A total of 332 and 323 markers were mapped in the two populations. Markers were distributed in each map over 21 linkage groups and covered an average of 2,200 cM of the C. pepo genome. The two maps had 62 loci in common, which enabled identification of 14 homologous linkage groups. Polyacrylamide gel analyses allowed detection of a high number of markers suitable for mapping, 10% of which were co-dominant RAPD loci. In the Pumpkin-Zucchini population, bulked segregant analysis (BSA) identified seven markers less than 7 cM distant from the locus n, affecting lignification of the seed coat. One of these markers, linked to the recessive hull-less allele (AW11-420), was also found in the Pumpkin-Crookneck population, 4 cM from n. In the Pumpkin-Zucchini population, 24 RAPD markers, previously introduced into C. pepo from C. moschata, were mapped in two linkage groups (13 and 11 markers in LGpz1 and LGpz2, respectively), together with two sequence characterized amplified region (SCAR) markers linked to genes for resistance to ZYMV.