ENRIQUE RITTER - Academia.edu (original) (raw)

Papers by ENRIQUE RITTER

Research paper thumbnail of Utilization of SSR and cDNA markers for screening known QTLs for late blight ( Phytophthora infestans ) resistance in potato

Euphytica, 2009

All published QTLs and genes for Phytophthora resistance were projected onto the bins of a high-d... more All published QTLs and genes for Phytophthora resistance were projected onto the bins of a high-density reference map of potato. Further, a transcriptome map containing around 700 cDNA-AFLP (TDF) markers was anchored to this map. We have analysed cDNA markers which are co-located with these resistance QTLs by cloning, sequencing and by performing homology searches in public sequence databases. Several interesting homologies were detected with typical resistance and stress response genes. On the other hand, we have screened all known QTL locations on the 12 potato chromosomes via linked SSR markers for the presence of a selectable QTL for Phytophthora resistance in four genetic backgrounds. Progenies descended from different Solanum wild species as resistance sources. Leaf and tuber resistances were analysed. In all case studies, several selectable QTLs were detected which descended from either parent. Tuber and leaf QTLs varied from progeny to progeny and between leaves and tubers. In none of the progenies were resistance levels of leaf and tuber blight correlated.

Research paper thumbnail of Short communication. Introgression of late blight (Phytophthora infestans L.) resistance from tuber-bearing Solanum wild species into cultivated potato

Research paper thumbnail of Papas Nativas - Un cultivo con potencial de alto valor añadido para la agricultura sostenible

Un consorcio de siete socios de seis países iberoamericanos ha evaluado diferentes propiedades de... more Un consorcio de siete socios de seis países iberoamericanos ha evaluado diferentes propiedades de una colección de Papas Nativas. Las evaluaciones incluyen resistencias a diferentes plagas y enfermedades, cualidades nutricionales y sustancias perjudiciales, comportamiento agronómico, análisis de la aptitud para el procesado y calidad organoléptica. Se han encontrado características favorables para todos los caracteres estudiados en algunos de los genotipos de Papas Nativas. Estos estudios se completaron con un análisis de la biodiversidad molecular existente para genes candidatos de resistencia y calidad.

Research paper thumbnail of Quantitative Resistance to Phytophthora infestans in Potato: A Case Study for QTL Mapping in an Allogamous Plant Species

Phytophthora infestans is the most important fungal pathogen in the cultivated potato (Solanum tu... more Phytophthora infestans is the most important fungal pathogen in the cultivated potato (Solanum tuberosum). Dominant, race-specific resistance alleles and quantitative resistance-the latter being more important for potato breeding-are found in the germplasm of cultivated and wild potato species. Quantitative trait loci (QTLs) for resistance to two races of P . infestans have been mapped in an F, progeny of a cross between non-inbred diploid potato parents with multiple alleles. Interval mapping methods based on highly informative restriction fragment length polymorphism markers revealed 11 chromosome segments on 9 potato chromosomes showing significant contrasts between marker genotypic classes. Whereas phenotypically no difference in quantitative resistance response was observed between the two fungal races, QTL mapping identified at least one race specific QT locus. Two QT regions coincided with two small segments on chromosomes Vand XZI to which the dominant alleles R1, conferring race specific resistance to P. infestans, Rxl and Rx2, both inducing extreme resistance to potato virus X, have been allocated in independent mapping experiments. Some minor QTLs were correlated with genetic loci for specific proteins related to pathogenesis, the expression of which is induced after infection with P. infestans.

Research paper thumbnail of RFLP maps of potato and their alignment with the homoeologous tomato genome

Theoretical and Applied Genetics, 1991

An RFLP linkage map of the potato is presented which comprises 304 loci derived from 230 DNA prob... more An RFLP linkage map of the potato is presented which comprises 304 loci derived from 230 DNA probes and one morphological marker (tuber skin color). The self-incompatibility locus of potato was mapped to chromosome I, which is homoeologous to tomato chromosome I. By mapping chromosome-specific tomato RFLP markers in potato and, vice versa, potato markers in tomato, the different potato and tomato RFLP maps were aligned to each other and the similarity of the potato and tomato genome was confirmed. The numbers given to the 12 potato chromosomes are now in accordance with the established tomato nomenclature. Comparisons between potato RFLP maps derived from different genetic backgrounds revealed conservation of marker order but differences in chromosome and total map length. In particular, significant reduction of map length was observed in interspecific compared to intraspecific crosses. The distribution of regions with distorted segregation ratios in the genome was analyzed for four potato parents. The most prominent distortion of recombination was found to be caused by the self-incompatibility locus.

Research paper thumbnail of The calculation of recombination frequencies in crosses of allogamous plant species with applications to linkage mapping

Research paper thumbnail of Cold Sweetening in Diploid Potato: Mapping Quantitative Trait Loci and Candidate Genes

A candidate gene approach has been used as a first step to identify the molecular basis of quanti... more A candidate gene approach has been used as a first step to identify the molecular basis of quantitative trait variation in potato. Sugar content of tubers upon cold storage was the model trait chosen because the metabolic pathways involved in starch and sugar metabolism are well known and many of the genes have been cloned. Tubers of two F 1 populations of diploid potato grown in six environments were evaluated for sugar content after cold storage. The populations were genotyped with RFLP, AFLP, and candidate gene markers. QTL analysis revealed that QTL for glucose, fructose, and sucrose content were located on all potato chromosomes. Most QTL for glucose content mapped to the same positions as QTL for fructose content. QTL explaining Ͼ10% of the variability for reducing sugars were located on linkage groups I, III, VII, VIII, IX, and XI. QTL consistent across populations and/or environments were identified. QTL were linked to genes encoding invertase, sucrose synthase 3, sucrose phosphate synthase, ADP-glucose pyrophosphorylase, sucrose transporter 1, and a putative sucrose sensor. The results suggest that allelic variants of enzymes operating in carbohydrate metabolic pathways contribute to the genetic variation in cold sweetening.

Research paper thumbnail of Identification of RFLP markers closely linked to the H1 gene conferring resistance to Globodera rostochiensis in potato

Theoretical and Applied Genetics, 1993

Resistance to the root cyst nematode Globodera rostochiensis is an agronomic trait that is at pre... more Resistance to the root cyst nematode Globodera rostochiensis is an agronomic trait that is at present incorporated into most new potato varieties. Major dominant genes are available that originate from wild and cultivated Solanum species closely related to the cultivated European potato (Solanum tuberosum ssp. tuberosum). One of those genes, H1, from S. Tuberosum ssp. andigena, was mapped to a distal position on potato chromosome V using restriction fragment length polymorphism (RFLP) markers. The H1 locus segregates independently from Gro1, a second dominant gene presumably from S. Spegazzinii that confers resistance to G. Rostochiensis and which has been mapped to chromosome VII. One marker, CP113, was linked without recombination to the H1 locus.

Research paper thumbnail of RFLP mapping on potato chromosomes of two genes controlling extreme resistance to potato virus X (PVX

Molecular and General Genetics, 1991

Two different chromosomal locations of major genes controlling extreme resistance to potato virus... more Two different chromosomal locations of major genes controlling extreme resistance to potato virus X (PVX) were found by restriction fragment length polymorphism (RFLP) analysis of two populations segregating for the resistance. The resistance geneRx1 mapped to the distal end of chromosome XII, whereasRx2 was located at an intermediate position on linkage group V in a region where reduced recombination and segregation distortion have also been observed. These linkage anomalies were due to abnormal behaviour of the chromosome contributed by the resistant parent P34. The results presented were obtained using two different strategies for mapping genes of unknown location. One approach was the use of probes revealing polymorphic loci spread throughout the genome and resulted in the mapping ofRx1. The second approach was based on the assumption of possible linkage between the resistance gene and clone-specific DNA fragments introduced from a wild potato species.Rx2 was mapped by adopting this strategy.

Research paper thumbnail of Identification of 2n breeding lines and 4n varieties of potato ( Solanum tuberosum , ssp. tuberosum ) with RFLP-fingerprints

Theoretical and Applied Genetics, 1989

The possibility of genotype identification with RFLP fingerprints was examined with 20 tetraploid... more The possibility of genotype identification with RFLP fingerprints was examined with 20 tetraploid potato varieties and 38 diploid potato lines. By using a sensitive detection system for small restriction fragment length differences and highly variable potato sequences as probes, all genotypes (diploids and tetraploids) were distinguished by a minimum of two probe/enzyme combinations. The best single probe/enzyme combination distinguished 19 out of 20 4n varieties and 33 out of 38 2n lines. Intravarietal variability was very small compared to the intervarietal variability, and patterns obtained with different DNA sources of the same genotype were identical.

Research paper thumbnail of Estimation of Recombination Frequencies and Construction of RFLP Linkage Maps in Plants From Crosses Between Heterozygous Parents

The construction of a restriction fragment length polymorphism (RFLP) linkage map is based on the... more The construction of a restriction fragment length polymorphism (RFLP) linkage map is based on the estimation of recombination frequencies between genetic loci and on the determination of the linear order of loci in linkage groups. RFLP loci can be identified as segregations of singular or allelic DNA-restriction fragments. From crosses between heterozygous individuals several allele (fragment) configurations are possible, and this leads to a set of formulas for the evaluation ofp, the recombination frequency between two loci. Tables and figures are presented illustrating a general outline of gene mapping using heterozygous populations. The method encompasses as special cases the mapping of loci from segregating populations of pure lines. Formulas for deriving the recombination frequencies and information functions are given for different fragment configurations. Information functions derived for relevant configurations are also compared. A procedure for map construction is presented, as it has been applied to RFLP mapping in an allogamous crop.

Research paper thumbnail of Localization by restriction fragment length polymorphism mapping in potato of a major dominant gene conferring resistance to the potato cyst nematode Globodera rostocbiensis

Molecular and General Genetics, 1990

A major dominant locus conferring resistance against several pathotypes of the root cyst nematode... more A major dominant locus conferring resistance against several pathotypes of the root cyst nematode Globodera rostochiensis was mapped on the linkage map of potato using restriction fragment length polymorphism (RFLP) markers. The assessment of resistance versus susceptibility of the plants in the experimental population considered was based on an in vivo (pot) and an in vitro (petri dish) test. By linkage to nine RFLP markers the resistance locus Gro1 was assigned to the potato linkage group IX which is homologous to the tomato linkage group 7. Deviations from the additivity of recombination frequencies between Gro1 and its neighbouring markers in the pot test led to the detection of a few phenotypic misclassifications of small plants with poor root systems that limited the observation of cysts on susceptible roots. Pooled data from both tests provided better estimates of recombination frequencies in the linkage interval defined by the markers flanking the resistance locus.

Research paper thumbnail of RFLP analysis and linkage mapping in Solanum tuberosum

Theoretical and Applied Genetics, 1989

A morphologically and agronomically heterogeneous collection of 38 diploid potato lines was analy... more A morphologically and agronomically heterogeneous collection of 38 diploid potato lines was analysed for restriction fragment length polymorphisms (RFLPs) with 168 potato probes, including random genomic and cDNA sequences as well as characterized potato genes of known function. The use of four cutter restriction enzymes and a fragment separation range from 250 to 2,000 bases on denaturing polyacrylamide gels allowed the detection of RFLPs of a few nucleotides. With this system, 90% of all probes tested showed useful polymorphism, and 95% of those were polymorphic with two or all three enzymes used. On the average, 80% of the probes were informative in all pairwise comparisons of the 38 lines with a minimum of 49% and a maximum of 95%. The percentage of heterozygosity was determined relative to each other for each line and indicated that direct segregation analysis in F1 populations should be feasible for most combinations. From a backcross involving one pair of the 38 lines, a RFLP linkage map with 141 loci was constructed, covering 690 cMorgan of the Solanum tuberosum genome.

Research paper thumbnail of Restriction Fragment Length Polymorphism-Mediated Targeting of the ml-o Resistance Locus in Barley (Hordeum vulgare

Proceedings of The National Academy of Sciences, 1991

The ml-o locus in barley confers resistance to all known races of the fungus Erysiphe graminis f.... more The ml-o locus in barley confers resistance to all known races of the fungus Erysiphe graminis f.sp. hordei. Since the molecular mechanisms underlying ml.o-mediated resistance are currently undefined, experiments have been initiated to isolate the gene by means of its map position. A collection of backcross lines containing ml-o alleles derived from six barley genotypes allowed us to identify a set of DNA markers very tightly linked to the resistance locus. These

Research paper thumbnail of RFLP markers for sugar beet breeding: chromosomal linkage maps and location of major genes for rhizomania resistance, monogermy and hypocotyl colour

Plant Journal, 1992

An RFLP linkage map for the nine chromosomes of sugar beet (Beta vulgaris L. ssp. vulgarisvar. al... more An RFLP linkage map for the nine chromosomes of sugar beet (Beta vulgaris L. ssp. vulgarisvar. altissima Doell) was constructed by using a segregating population from a cross between two plants which were heterozygous for several agronomically interesting characters. One hundred and eleven RFLP loci have been mapped to nine linkage groups using 92 genomic markers. The current RFLP map covers a total length of 540 cM. Evidence for the existence of a major gene for rhizomania resistance ( R r l ) is given, together with its map position on linkage group IV in the interval between loci GS44 and GS28a. The presence of an RFLP fragment at the GS3dlocus is, until now, the best molecular marker for rhizomania-resistant genotypes in segregating populations of sugar beet; GS3d is linked to Rrl with 6.7 cM. The gene MM, controlling the polygerm/monogerm seed type, has been mapped on linkage group IX in a distal position at 4.2 cM from the locus GS7. The gene Rcontrolling the hypocotyl colour maps to linkage group VII and does not recombine with the RFLP locus GS42. The inheritance of a group of RFLP loci revealed the possible presence of a translocation in the population used to establish the map. The data presented are discussed in relation to the possibility of using RFLP markers in sugar beet breeding.

Research paper thumbnail of Analysis of quantitative trait loci (QTLs) and quantitative trait alleles (QTAs) for potato tuber yield and starch content

Theoretical and Applied Genetics, 1998

Using RFLP markers, QTLs for tuber starch-content and tuber yield were mapped in two F1 populati... more Using RFLP markers, QTLs for tuber starch-content and tuber yield were mapped in two F1 populations derived from crossing non-inbred di-haploid potato breeding lines. QTLs were identified and mapped, based on both single-marker tests and interval analyses. A model specifically developed for interval QTL analysis in non-inbred plant species was successfully applied for the first time to experimental data. Results of both methods of QTL analysis were similar but not identical. QTLs for tuber starch-content and tuber yield were analysed in segregating populations K31 and LH in five and two environments, respectively. Population K31 was fully genotyped whereas population LH was selectively genotyped according to high and low tuber-starch content. Eighteen putative QTLs for tuber starch-content were identified on all 12 potato linkage groups and eight putative QTLs for tuber yield were identified on eight linkage groups. Twenty of twenty six putative QTLs were reproducibly detected in at least two environments and/or mapping populations. Few major QTLs for tuber starch-content were highly stable across environments but were detected in only one of the two mapping populations analysed. Most QTLs for tuber yield were linked with QTLs for tuber starch-content suggesting that the effects on both traits are controlled by the same genetic factors. The results are discussed with respect to marker-assisted selection in potato.

Research paper thumbnail of An extended map of the sugar beet genome containing RFLP and RAPD loci

Theoretical and Applied Genetics, 1995

An updated map of sugar beet (Beta vulgaris L. ssp. vulgaris var ‘altissima Doell’) is presented.... more An updated map of sugar beet (Beta vulgaris L. ssp. vulgaris var ‘altissima Doell’) is presented. In this genetic map we have combined 248 RFLP and 50 RAPD loci. Including the loci for rhizomania resistance Rr1, hypocotyl colour R and the locus controlling the monogerm character M, 301 loci have now been mapped to the nine linkage groups covering 815 cM. In addition, the karyotype of some of the Beta vulgaris chromosomes has been correlated with existing RFLP and RAPD linkage maps.

Research paper thumbnail of Discrimination among 136 Tetraploid Potato Varieties by Fingerprints Using Highly Polymorphic DNA Markers

Crop Science, 1992

... Erna, Emtestolz, Eroica, Fantasia, Fausta, Forelle, Fortuna, Franca, Frila, Gabi, Gesa, Glori... more ... Erna, Emtestolz, Eroica, Fantasia, Fausta, Forelle, Fortuna, Franca, Frila, Gabi, Gesa, Gloria, Grandifolia, Granola, Grata, Gusto, Hansa, Heidrun ... Rebecca, Rikea, Rita, Rosita, Roxy, Ruslea, Russet Burbank, Rustica, Sandra, Saphir, Saskia, Saturna, Sekura, Selma, Semena, Sie ...

Research paper thumbnail of Quantitative Resistance to Phytophthora infestans in Potato: A Case Study for QTL Mapping in an Allogamous Plant Species

Phytophthora infestans is the most important fungal pathogen in the cultivated potato (Solanum tu... more Phytophthora infestans is the most important fungal pathogen in the cultivated potato (Solanum tuberosum). Dominant, race-specific resistance alleles and quantitative resistance-the latter being more important for potato breeding-are found in the germplasm of cultivated and wild potato species. Quantitative trait loci (QTLs) for resistance to two races of P . infestans have been mapped in an F, progeny of a cross between non-inbred diploid potato parents with multiple alleles. Interval mapping methods based on highly informative restriction fragment length polymorphism markers revealed 11 chromosome segments on 9 potato chromosomes showing significant contrasts between marker genotypic classes. Whereas phenotypically no difference in quantitative resistance response was observed between the two fungal races, QTL mapping identified at least one race specific QT locus. Two QT regions coincided with two small segments on chromosomes Vand XZI to which the dominant alleles R1, conferring race specific resistance to P. infestans, Rxl and Rx2, both inducing extreme resistance to potato virus X, have been allocated in independent mapping experiments. Some minor QTLs were correlated with genetic loci for specific proteins related to pathogenesis, the expression of which is induced after infection with P. infestans.

Research paper thumbnail of RFLP maps of potato and their alignment with the homoeologous tomato genome

Theoretical and Applied Genetics, 1991

An RFLP linkage map of the potato is presented which comprises 304 loci derived from 230 DNA prob... more An RFLP linkage map of the potato is presented which comprises 304 loci derived from 230 DNA probes and one morphological marker (tuber skin color). The self-incompatibility locus of potato was mapped to chromosome I, which is homoeologous to tomato chromosome I. By mapping chromosome-specific tomato RFLP markers in potato and, vice versa, potato markers in tomato, the different potato and tomato RFLP maps were aligned to each other and the similarity of the potato and tomato genome was confirmed. The numbers given to the 12 potato chromosomes are now in accordance with the established tomato nomenclature. Comparisons between potato RFLP maps derived from different genetic backgrounds revealed conservation of marker order but differences in chromosome and total map length. In particular, significant reduction of map length was observed in interspecific compared to intraspecific crosses. The distribution of regions with distorted segregation ratios in the genome was analyzed for four potato parents. The most prominent distortion of recombination was found to be caused by the self-incompatibility locus.

Research paper thumbnail of Utilization of SSR and cDNA markers for screening known QTLs for late blight ( Phytophthora infestans ) resistance in potato

Euphytica, 2009

All published QTLs and genes for Phytophthora resistance were projected onto the bins of a high-d... more All published QTLs and genes for Phytophthora resistance were projected onto the bins of a high-density reference map of potato. Further, a transcriptome map containing around 700 cDNA-AFLP (TDF) markers was anchored to this map. We have analysed cDNA markers which are co-located with these resistance QTLs by cloning, sequencing and by performing homology searches in public sequence databases. Several interesting homologies were detected with typical resistance and stress response genes. On the other hand, we have screened all known QTL locations on the 12 potato chromosomes via linked SSR markers for the presence of a selectable QTL for Phytophthora resistance in four genetic backgrounds. Progenies descended from different Solanum wild species as resistance sources. Leaf and tuber resistances were analysed. In all case studies, several selectable QTLs were detected which descended from either parent. Tuber and leaf QTLs varied from progeny to progeny and between leaves and tubers. In none of the progenies were resistance levels of leaf and tuber blight correlated.

Research paper thumbnail of Short communication. Introgression of late blight (Phytophthora infestans L.) resistance from tuber-bearing Solanum wild species into cultivated potato

Research paper thumbnail of Papas Nativas - Un cultivo con potencial de alto valor añadido para la agricultura sostenible

Un consorcio de siete socios de seis países iberoamericanos ha evaluado diferentes propiedades de... more Un consorcio de siete socios de seis países iberoamericanos ha evaluado diferentes propiedades de una colección de Papas Nativas. Las evaluaciones incluyen resistencias a diferentes plagas y enfermedades, cualidades nutricionales y sustancias perjudiciales, comportamiento agronómico, análisis de la aptitud para el procesado y calidad organoléptica. Se han encontrado características favorables para todos los caracteres estudiados en algunos de los genotipos de Papas Nativas. Estos estudios se completaron con un análisis de la biodiversidad molecular existente para genes candidatos de resistencia y calidad.

Research paper thumbnail of Quantitative Resistance to Phytophthora infestans in Potato: A Case Study for QTL Mapping in an Allogamous Plant Species

Phytophthora infestans is the most important fungal pathogen in the cultivated potato (Solanum tu... more Phytophthora infestans is the most important fungal pathogen in the cultivated potato (Solanum tuberosum). Dominant, race-specific resistance alleles and quantitative resistance-the latter being more important for potato breeding-are found in the germplasm of cultivated and wild potato species. Quantitative trait loci (QTLs) for resistance to two races of P . infestans have been mapped in an F, progeny of a cross between non-inbred diploid potato parents with multiple alleles. Interval mapping methods based on highly informative restriction fragment length polymorphism markers revealed 11 chromosome segments on 9 potato chromosomes showing significant contrasts between marker genotypic classes. Whereas phenotypically no difference in quantitative resistance response was observed between the two fungal races, QTL mapping identified at least one race specific QT locus. Two QT regions coincided with two small segments on chromosomes Vand XZI to which the dominant alleles R1, conferring race specific resistance to P. infestans, Rxl and Rx2, both inducing extreme resistance to potato virus X, have been allocated in independent mapping experiments. Some minor QTLs were correlated with genetic loci for specific proteins related to pathogenesis, the expression of which is induced after infection with P. infestans.

Research paper thumbnail of RFLP maps of potato and their alignment with the homoeologous tomato genome

Theoretical and Applied Genetics, 1991

An RFLP linkage map of the potato is presented which comprises 304 loci derived from 230 DNA prob... more An RFLP linkage map of the potato is presented which comprises 304 loci derived from 230 DNA probes and one morphological marker (tuber skin color). The self-incompatibility locus of potato was mapped to chromosome I, which is homoeologous to tomato chromosome I. By mapping chromosome-specific tomato RFLP markers in potato and, vice versa, potato markers in tomato, the different potato and tomato RFLP maps were aligned to each other and the similarity of the potato and tomato genome was confirmed. The numbers given to the 12 potato chromosomes are now in accordance with the established tomato nomenclature. Comparisons between potato RFLP maps derived from different genetic backgrounds revealed conservation of marker order but differences in chromosome and total map length. In particular, significant reduction of map length was observed in interspecific compared to intraspecific crosses. The distribution of regions with distorted segregation ratios in the genome was analyzed for four potato parents. The most prominent distortion of recombination was found to be caused by the self-incompatibility locus.

Research paper thumbnail of The calculation of recombination frequencies in crosses of allogamous plant species with applications to linkage mapping

Research paper thumbnail of Cold Sweetening in Diploid Potato: Mapping Quantitative Trait Loci and Candidate Genes

A candidate gene approach has been used as a first step to identify the molecular basis of quanti... more A candidate gene approach has been used as a first step to identify the molecular basis of quantitative trait variation in potato. Sugar content of tubers upon cold storage was the model trait chosen because the metabolic pathways involved in starch and sugar metabolism are well known and many of the genes have been cloned. Tubers of two F 1 populations of diploid potato grown in six environments were evaluated for sugar content after cold storage. The populations were genotyped with RFLP, AFLP, and candidate gene markers. QTL analysis revealed that QTL for glucose, fructose, and sucrose content were located on all potato chromosomes. Most QTL for glucose content mapped to the same positions as QTL for fructose content. QTL explaining Ͼ10% of the variability for reducing sugars were located on linkage groups I, III, VII, VIII, IX, and XI. QTL consistent across populations and/or environments were identified. QTL were linked to genes encoding invertase, sucrose synthase 3, sucrose phosphate synthase, ADP-glucose pyrophosphorylase, sucrose transporter 1, and a putative sucrose sensor. The results suggest that allelic variants of enzymes operating in carbohydrate metabolic pathways contribute to the genetic variation in cold sweetening.

Research paper thumbnail of Identification of RFLP markers closely linked to the H1 gene conferring resistance to Globodera rostochiensis in potato

Theoretical and Applied Genetics, 1993

Resistance to the root cyst nematode Globodera rostochiensis is an agronomic trait that is at pre... more Resistance to the root cyst nematode Globodera rostochiensis is an agronomic trait that is at present incorporated into most new potato varieties. Major dominant genes are available that originate from wild and cultivated Solanum species closely related to the cultivated European potato (Solanum tuberosum ssp. tuberosum). One of those genes, H1, from S. Tuberosum ssp. andigena, was mapped to a distal position on potato chromosome V using restriction fragment length polymorphism (RFLP) markers. The H1 locus segregates independently from Gro1, a second dominant gene presumably from S. Spegazzinii that confers resistance to G. Rostochiensis and which has been mapped to chromosome VII. One marker, CP113, was linked without recombination to the H1 locus.

Research paper thumbnail of RFLP mapping on potato chromosomes of two genes controlling extreme resistance to potato virus X (PVX

Molecular and General Genetics, 1991

Two different chromosomal locations of major genes controlling extreme resistance to potato virus... more Two different chromosomal locations of major genes controlling extreme resistance to potato virus X (PVX) were found by restriction fragment length polymorphism (RFLP) analysis of two populations segregating for the resistance. The resistance geneRx1 mapped to the distal end of chromosome XII, whereasRx2 was located at an intermediate position on linkage group V in a region where reduced recombination and segregation distortion have also been observed. These linkage anomalies were due to abnormal behaviour of the chromosome contributed by the resistant parent P34. The results presented were obtained using two different strategies for mapping genes of unknown location. One approach was the use of probes revealing polymorphic loci spread throughout the genome and resulted in the mapping ofRx1. The second approach was based on the assumption of possible linkage between the resistance gene and clone-specific DNA fragments introduced from a wild potato species.Rx2 was mapped by adopting this strategy.

Research paper thumbnail of Identification of 2n breeding lines and 4n varieties of potato ( Solanum tuberosum , ssp. tuberosum ) with RFLP-fingerprints

Theoretical and Applied Genetics, 1989

The possibility of genotype identification with RFLP fingerprints was examined with 20 tetraploid... more The possibility of genotype identification with RFLP fingerprints was examined with 20 tetraploid potato varieties and 38 diploid potato lines. By using a sensitive detection system for small restriction fragment length differences and highly variable potato sequences as probes, all genotypes (diploids and tetraploids) were distinguished by a minimum of two probe/enzyme combinations. The best single probe/enzyme combination distinguished 19 out of 20 4n varieties and 33 out of 38 2n lines. Intravarietal variability was very small compared to the intervarietal variability, and patterns obtained with different DNA sources of the same genotype were identical.

Research paper thumbnail of Estimation of Recombination Frequencies and Construction of RFLP Linkage Maps in Plants From Crosses Between Heterozygous Parents

The construction of a restriction fragment length polymorphism (RFLP) linkage map is based on the... more The construction of a restriction fragment length polymorphism (RFLP) linkage map is based on the estimation of recombination frequencies between genetic loci and on the determination of the linear order of loci in linkage groups. RFLP loci can be identified as segregations of singular or allelic DNA-restriction fragments. From crosses between heterozygous individuals several allele (fragment) configurations are possible, and this leads to a set of formulas for the evaluation ofp, the recombination frequency between two loci. Tables and figures are presented illustrating a general outline of gene mapping using heterozygous populations. The method encompasses as special cases the mapping of loci from segregating populations of pure lines. Formulas for deriving the recombination frequencies and information functions are given for different fragment configurations. Information functions derived for relevant configurations are also compared. A procedure for map construction is presented, as it has been applied to RFLP mapping in an allogamous crop.

Research paper thumbnail of Localization by restriction fragment length polymorphism mapping in potato of a major dominant gene conferring resistance to the potato cyst nematode Globodera rostocbiensis

Molecular and General Genetics, 1990

A major dominant locus conferring resistance against several pathotypes of the root cyst nematode... more A major dominant locus conferring resistance against several pathotypes of the root cyst nematode Globodera rostochiensis was mapped on the linkage map of potato using restriction fragment length polymorphism (RFLP) markers. The assessment of resistance versus susceptibility of the plants in the experimental population considered was based on an in vivo (pot) and an in vitro (petri dish) test. By linkage to nine RFLP markers the resistance locus Gro1 was assigned to the potato linkage group IX which is homologous to the tomato linkage group 7. Deviations from the additivity of recombination frequencies between Gro1 and its neighbouring markers in the pot test led to the detection of a few phenotypic misclassifications of small plants with poor root systems that limited the observation of cysts on susceptible roots. Pooled data from both tests provided better estimates of recombination frequencies in the linkage interval defined by the markers flanking the resistance locus.

Research paper thumbnail of RFLP analysis and linkage mapping in Solanum tuberosum

Theoretical and Applied Genetics, 1989

A morphologically and agronomically heterogeneous collection of 38 diploid potato lines was analy... more A morphologically and agronomically heterogeneous collection of 38 diploid potato lines was analysed for restriction fragment length polymorphisms (RFLPs) with 168 potato probes, including random genomic and cDNA sequences as well as characterized potato genes of known function. The use of four cutter restriction enzymes and a fragment separation range from 250 to 2,000 bases on denaturing polyacrylamide gels allowed the detection of RFLPs of a few nucleotides. With this system, 90% of all probes tested showed useful polymorphism, and 95% of those were polymorphic with two or all three enzymes used. On the average, 80% of the probes were informative in all pairwise comparisons of the 38 lines with a minimum of 49% and a maximum of 95%. The percentage of heterozygosity was determined relative to each other for each line and indicated that direct segregation analysis in F1 populations should be feasible for most combinations. From a backcross involving one pair of the 38 lines, a RFLP linkage map with 141 loci was constructed, covering 690 cMorgan of the Solanum tuberosum genome.

Research paper thumbnail of Restriction Fragment Length Polymorphism-Mediated Targeting of the ml-o Resistance Locus in Barley (Hordeum vulgare

Proceedings of The National Academy of Sciences, 1991

The ml-o locus in barley confers resistance to all known races of the fungus Erysiphe graminis f.... more The ml-o locus in barley confers resistance to all known races of the fungus Erysiphe graminis f.sp. hordei. Since the molecular mechanisms underlying ml.o-mediated resistance are currently undefined, experiments have been initiated to isolate the gene by means of its map position. A collection of backcross lines containing ml-o alleles derived from six barley genotypes allowed us to identify a set of DNA markers very tightly linked to the resistance locus. These

Research paper thumbnail of RFLP markers for sugar beet breeding: chromosomal linkage maps and location of major genes for rhizomania resistance, monogermy and hypocotyl colour

Plant Journal, 1992

An RFLP linkage map for the nine chromosomes of sugar beet (Beta vulgaris L. ssp. vulgarisvar. al... more An RFLP linkage map for the nine chromosomes of sugar beet (Beta vulgaris L. ssp. vulgarisvar. altissima Doell) was constructed by using a segregating population from a cross between two plants which were heterozygous for several agronomically interesting characters. One hundred and eleven RFLP loci have been mapped to nine linkage groups using 92 genomic markers. The current RFLP map covers a total length of 540 cM. Evidence for the existence of a major gene for rhizomania resistance ( R r l ) is given, together with its map position on linkage group IV in the interval between loci GS44 and GS28a. The presence of an RFLP fragment at the GS3dlocus is, until now, the best molecular marker for rhizomania-resistant genotypes in segregating populations of sugar beet; GS3d is linked to Rrl with 6.7 cM. The gene MM, controlling the polygerm/monogerm seed type, has been mapped on linkage group IX in a distal position at 4.2 cM from the locus GS7. The gene Rcontrolling the hypocotyl colour maps to linkage group VII and does not recombine with the RFLP locus GS42. The inheritance of a group of RFLP loci revealed the possible presence of a translocation in the population used to establish the map. The data presented are discussed in relation to the possibility of using RFLP markers in sugar beet breeding.

Research paper thumbnail of Analysis of quantitative trait loci (QTLs) and quantitative trait alleles (QTAs) for potato tuber yield and starch content

Theoretical and Applied Genetics, 1998

Using RFLP markers, QTLs for tuber starch-content and tuber yield were mapped in two F1 populati... more Using RFLP markers, QTLs for tuber starch-content and tuber yield were mapped in two F1 populations derived from crossing non-inbred di-haploid potato breeding lines. QTLs were identified and mapped, based on both single-marker tests and interval analyses. A model specifically developed for interval QTL analysis in non-inbred plant species was successfully applied for the first time to experimental data. Results of both methods of QTL analysis were similar but not identical. QTLs for tuber starch-content and tuber yield were analysed in segregating populations K31 and LH in five and two environments, respectively. Population K31 was fully genotyped whereas population LH was selectively genotyped according to high and low tuber-starch content. Eighteen putative QTLs for tuber starch-content were identified on all 12 potato linkage groups and eight putative QTLs for tuber yield were identified on eight linkage groups. Twenty of twenty six putative QTLs were reproducibly detected in at least two environments and/or mapping populations. Few major QTLs for tuber starch-content were highly stable across environments but were detected in only one of the two mapping populations analysed. Most QTLs for tuber yield were linked with QTLs for tuber starch-content suggesting that the effects on both traits are controlled by the same genetic factors. The results are discussed with respect to marker-assisted selection in potato.

Research paper thumbnail of An extended map of the sugar beet genome containing RFLP and RAPD loci

Theoretical and Applied Genetics, 1995

An updated map of sugar beet (Beta vulgaris L. ssp. vulgaris var ‘altissima Doell’) is presented.... more An updated map of sugar beet (Beta vulgaris L. ssp. vulgaris var ‘altissima Doell’) is presented. In this genetic map we have combined 248 RFLP and 50 RAPD loci. Including the loci for rhizomania resistance Rr1, hypocotyl colour R and the locus controlling the monogerm character M, 301 loci have now been mapped to the nine linkage groups covering 815 cM. In addition, the karyotype of some of the Beta vulgaris chromosomes has been correlated with existing RFLP and RAPD linkage maps.

Research paper thumbnail of Discrimination among 136 Tetraploid Potato Varieties by Fingerprints Using Highly Polymorphic DNA Markers

Crop Science, 1992

... Erna, Emtestolz, Eroica, Fantasia, Fausta, Forelle, Fortuna, Franca, Frila, Gabi, Gesa, Glori... more ... Erna, Emtestolz, Eroica, Fantasia, Fausta, Forelle, Fortuna, Franca, Frila, Gabi, Gesa, Gloria, Grandifolia, Granola, Grata, Gusto, Hansa, Heidrun ... Rebecca, Rikea, Rita, Rosita, Roxy, Ruslea, Russet Burbank, Rustica, Sandra, Saphir, Saskia, Saturna, Sekura, Selma, Semena, Sie ...

Research paper thumbnail of Quantitative Resistance to Phytophthora infestans in Potato: A Case Study for QTL Mapping in an Allogamous Plant Species

Phytophthora infestans is the most important fungal pathogen in the cultivated potato (Solanum tu... more Phytophthora infestans is the most important fungal pathogen in the cultivated potato (Solanum tuberosum). Dominant, race-specific resistance alleles and quantitative resistance-the latter being more important for potato breeding-are found in the germplasm of cultivated and wild potato species. Quantitative trait loci (QTLs) for resistance to two races of P . infestans have been mapped in an F, progeny of a cross between non-inbred diploid potato parents with multiple alleles. Interval mapping methods based on highly informative restriction fragment length polymorphism markers revealed 11 chromosome segments on 9 potato chromosomes showing significant contrasts between marker genotypic classes. Whereas phenotypically no difference in quantitative resistance response was observed between the two fungal races, QTL mapping identified at least one race specific QT locus. Two QT regions coincided with two small segments on chromosomes Vand XZI to which the dominant alleles R1, conferring race specific resistance to P. infestans, Rxl and Rx2, both inducing extreme resistance to potato virus X, have been allocated in independent mapping experiments. Some minor QTLs were correlated with genetic loci for specific proteins related to pathogenesis, the expression of which is induced after infection with P. infestans.

Research paper thumbnail of RFLP maps of potato and their alignment with the homoeologous tomato genome

Theoretical and Applied Genetics, 1991

An RFLP linkage map of the potato is presented which comprises 304 loci derived from 230 DNA prob... more An RFLP linkage map of the potato is presented which comprises 304 loci derived from 230 DNA probes and one morphological marker (tuber skin color). The self-incompatibility locus of potato was mapped to chromosome I, which is homoeologous to tomato chromosome I. By mapping chromosome-specific tomato RFLP markers in potato and, vice versa, potato markers in tomato, the different potato and tomato RFLP maps were aligned to each other and the similarity of the potato and tomato genome was confirmed. The numbers given to the 12 potato chromosomes are now in accordance with the established tomato nomenclature. Comparisons between potato RFLP maps derived from different genetic backgrounds revealed conservation of marker order but differences in chromosome and total map length. In particular, significant reduction of map length was observed in interspecific compared to intraspecific crosses. The distribution of regions with distorted segregation ratios in the genome was analyzed for four potato parents. The most prominent distortion of recombination was found to be caused by the self-incompatibility locus.