A reexamination of infraspecific taxa of a wild potato,Solanum microdontum (Solanum sect.Petota:Solanaceae)

Current taxonomic interpretations ofSolanum microdontum Bitter partition the species into two or three infraspecific taxa, variously recognized as subspecies or varieties. The present study reexamines these taxa using morphological data from four individuals each of 69 accessions from most of the range of the species, planted in a common field plot. Our results show that the character states used to recognize infraspecific taxa inS. microdontum often vary within accessions and have no correlation with geography. We conclude that past hypotheses have used typological concepts and that infraspecific taxa are not warranted. This study questions other hypotheses of infraspecific taxa in sect.Petota.     

Plant regeneration from the protoplasts of Solanum tuberosum, S. nigrum and S. bulbocastanum

The mesophyll protoplasts were isolated from the Solanum tuberosum (S. tbr) clones of different ploidy level (4x Bzura cv., 2x H-8105, and 2x ZEL-1136) as well as from the wild species: S. bulbocastanum (S. blb, 2x) and two accessions of S. nigrum (S. ngr, 6x). Additionally, the protoplasts were isolated from the cell suspensions of Bzura cv. and H-8105 clone. The conditions of protoplast isolation as well as the media for their culturing and regeneration, were selected and optimized for the studied genotypes. For mesophyll protoplasts, the shooting calli were produced by all the cultured protoclones except that of S. bulbocastanum. The shoots excised from the protoplast-derived calli developed into whole plants in all the studied potato clones but only in one accession of S. nigrum, i.e. S. ngr var. gigantea. As for suspension-cell-derived protoplasts, only H-8105 clone produced the regenerative type of calli, though normal shoots could not be obtained. The regenerative capacity of the protoplasts isolated from leaves and cell suspensions is compared and discussed. We regret to report the death of M. Sc. Maria Borkowska after the completion of this work.     

Taxonomy of North and Central American diploid wild potato (Solanum sect. Petota) species: AFLP data

Solanum section Petota, the potato and its wild relatives, includes about 200 wild species distributed from the southwestern United States to central Argentina and adjacent Chile, with about 30 species in North and Central America. The North/Central American region and the South American region all include diploids, tetraploids, and hexaploids. Chloroplast DNA restriction enzyme data from a prior study showed that 13 of the North/Central American species formed a clade containing only diploids, but there was low resolution within the clade. This Amplified Fragment Length Polymorphism (AFLP) study is conducted to provide additional resolution within the North/Central American diploids and complements the chloroplast results, and prior morphological results. Wagner parsimony and phenetic analyses mostly agreed with the morphological data in supporting currently recognized species except that they suggest that S. brachistotrichium and S. stenophyllidium are conspecific. Our new AFLP data, in combination with the cpDNA and morphological data, also support sister taxon relationships for the following diploid species from North and Central America: 1) S. cardiophyllum subsp. ehrenbergii and S. stenophyllidium, 2) S. tarnii and S. trifidum, 3) S. jamesii and S. pinnatisectum, 4) S. lesteri and S. polyadenium, and 5) S. clarum and S. morelliforme.This work represents partial fulfillment for the requirements of a Ph.D. degree in Plant Breeding and Genetics at the University of Wisconsin-Madison. We thank committee members Paul Berry, Michael Havey, Thomas Osborn, and Kenneth Sytsma. We also thank John Bamberg and Staff of the Unites States Potato Genebank for germplasm and locality data; Charles Nicolet and staff of the University of Wisconsin Biotechnology Center for technical help; Lynn Hummel and staff at Walnut Street Greenhouse for help in growing plants; and lab partners Brian Karas, Iris Peralta, Celeste Raker, and Sarah Stephenson for technical advice. This study was supported by CONACYT (Mexico) scholarship number 116742 granted to Sabina I. Lara-Cabrera, and the United States Department of Agriculture. Names are necessary to report data. However, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable.     

The use and limits of AFLP data in the taxonomy of polyploid wild potato species in Solanum series Conicibaccata

Solanum sect. Petota (tuber-bearing wild and cultivated potatoes) are a group of approximately 190 wild species distributed throughout the Americas from the southwestern United States south to Argentina, Chile, and Uruguay. Solanum series Conicibaccata are a group of approximately 40 species within sect. Petota, distributed from central Mexico to central Bolivia, composed of diploids (2n = 2x = 24), tetraploids (2n = 4x = 48) and hexaploids (2n = 6x = 64); the polyploids are thought to be polysomic polyploids. This study initially was designed to address species boundaries of the four Mexican and Central American species of series Conicibaccata with AFLP data with the addition of first germplasm collections of one of these four species, Solanum woodsonii, as a follow-up to prior morphological, chloroplast DNA, and RAPD studies; and additional species of series Conicibaccata from South America. AFLP data from 12 primer combinations (1722 polymorphic bands) are unable to distinguish polyploid species long thought to be distinct. The data suggest a complex reticulate history of the tetraploids or the need for a broad downward reevaluation of the number of species in series Conicibaccata, a trend seen in other series of sect. Petota. Separately, through flow cytometry, we report the first ploidy level of S. woodsonii, as tetraploid (2n = 48). The U.S. Government’s right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.     

Assessment of genetic diversity among and within Achillea species using amplified fragment length polymorphism (AFLP)

Amplified fragment length polymorphism (AFLP) markers were used to assess the genetic diversity of 57 Achillea accessions belonging to five species, A. millefolium, A. filipendulina, A. tenuifolia, A. santolina and A. biebersteinii. Nine AFLP primer combinations were used, which produced 301 polymorphic bands. In most species, a high level of genetic variation was detected among the genotypes. The Jaccard's similarity indices (J), based on AFLP profiles, were subjected to UPGMA cluster analysis. Application of Mantel's test for cophenetic correlation to the cluster analysis indicated the high fitness of the accessions to a group (r = 0.918). The dendrogram generated revealed five major groups corresponding to five species. The principle coordinate analysis (PCoA) data confirmed the results of the clustering. Among the species, A. teunifolia and A. santolina showed the greatest and the least genetic diversity, respectively. A. filipendulina accessions were acquired primarily from the same ecological regions of western Iran. Accessions belonging to A. biebersteinii originated from the Isfahan province and were separated from other species at the root of the dendrogram. The results of the clustering method, based on AFLP markers, corresponded closely with the geographical origins of the genotypes. The results of the present study could contribute to a better understanding and management of conservation and exploitation of the Achillea germplasm.     

Crossing relationships and chromosome numbers of Solanum section Solanum in Uganda

The ability of taxa to cross/hybridize is useful information for plant systematists and breeders. Crossability reflects reproductive isolation and the biological species concept stresses the need for reproductive isolation between species to maintain morphological distincness. For plant breeders knowledge on crossing ability facilitate selection of taxa for character improvement breeding. In this study, the crossing relationships and chromosome numbers within and among Ugandan species of Solanum sect. Solanum is studied by making 800 crosses involving 246 combinations. Less than half of these combinations were successful, producing F1 offspring. All studied accessions are self‐compatible and most accessions crossed readily with accessions of their own species. Interspecific crossings failed either to yield seeds, yielded F1 seeds that did not germinate, or resulted in F1s that did not have stainable pollen – implying a crossing barrier; or stainable pollen, but with chromosome numbers that indicated reproduction by apomixis. The results support the taxonomic treatment of Solanum based on classical, numerical and partly molecular evidences. The material studied represents eight Ugandan taxa: S. americanum, a diploid (2n = 2x = 24); five tetraploids (2n = 4x = 48) S. florulentum, S. memphiticum, S. tarderemotum, S. villosum ssp. villosum and S. villosum ssp. miniatum; and two hexaploids (2n = 6x = 72) S. scabrum subsp. scabrum and S. scabrum subsp. laevis. In addition to confirming the ploidy levels of the Ugandan accessions, the ploidy levels of S. florulentum, S. memphiticum and S. tarderemotum are reported for the first time. Non‐Ugandan material of Solanum sarrachoides was found to be diploid. Knowledge of the crossing behaviour and ploidy levels in Solanum will facilitate breeding for character improvement in these important species that are used commonly as food and/or medicine in eastern Africa.     

Origin of chloroplast DNA diversity in the Andean potatoes

Summary Wide chloroplast DNA (ctDNA) diversity has been reported in the Andean cultivated tetraploid potato, Solanum tuberosum ssp. andigena. Andean diploid potatoes were analyzed in this study to elucidate the origin of the diverse ctDNA variation of the cultivated tetraploids. The ctDNA types of 58 cultivated diploid potatoes (S. stenotomum, S. goniocalyx and S. phureja), 35 accessions of S. sparsipilum, a diploid weed species, and 40 accessions of the wild or weed species, S. chacoense, were determined based on ctDNA restriction fragment patterns of BamHI, HindIII and PvuII. Several different ctDNA types were found in the cultivated potatoes as well as in weed and wild potato species; thus, intraspecific ctDNA variation may be common in both wild and cultivated potato species and perhaps in the higher plant kingdom as a whole. The ctDNA variation range of cultivated diploid potatoes was similar to that of the tetraploid potatoes, suggesting that the ctDNA diversity of the tetraploid potato could have been introduced from cultivated diploid potatoes. This provided further evidence that the Andean cultivated tetraploid potato, ssp. andigena, could have arisen many times from the cultivated diploid populations. The diverse but conserved ctDNA variation noted in the Andean potatoes may have occurred in the early stage of species differentiation of South American tuber-bearing Solanums.     

High-resolution Mapping and Analysis of the Resistance Locus <Emphasis Type="Italic">Rpi-abpt</Emphasis> Against <Emphasis Type="Italic">Phytophthora infestans</Emphasis> in Potato

Introduction of more durable resistance against Phytophthora infestans causing late blight into the cultivated potato is of importance for sustainable agriculture. We identified a new monogenically inherited resistance locus that is localized on chromosome 4. The resistance is derived from an ABPT clone, which is originally a complex quadruple hybrid in which Solanum acaule, S. bulbocastanum, S. phureja and S. tuberosum were involved. Resistance data of the original resistant accessions of the wild species and analysis of mobility of AFLP markers linked to the resistance locus suggest that the resistance locus is originating from S. bulbocastanum. A population of 1383 genotypes was screened with two AFLP markers flanking the Rpi-abpt locus and 98 recombinants were identified. An accurate high-resolution map was constructed and the Rpi-abpt locus was localized in a 0.5 cM interval. One AFLP marker was found to co-segregate with the Rpi-abpt locus. Its DNA sequence was highly similar with sequences found on a tomato BAC containing several resistance gene analogues on chromosome 4 and its translated protein sequence appeared to be homologous to several disease resistance related proteins. The results indicated that the Rpi-abpt gene is a member of an R gene cluster.     

RFLP analysis of the wild potato species,Solanum acaule Bitter (Solanum sect. Petota)

Summary Intraspecific variation of a wild potato species, Solanum acaule Bitt., was analyzed by RFLPs of genomic DNA. One hundred and five accessions were selected throughout the distribution area, including all subspecies, i.e., ssp. albicans (hexaploid), ssp. punae (tetraploid), ssp. acaule (tetraploid) and ssp. aemulans (tetraploid). Twenty-seven low-copy DNA clones (probes) were Southern hybridized with EcoRI, EcoRV, HindIII, and XbaI digests of total DNA of all accessions. In total, 238 RFLPs were detected from 94 enzyme x probe combinations. Among them, 49 RFLPs were specific to ssp. albicans, suggesting that the additional third genome is distinct from its two other genomes. RFLPs between and within subspecies were analyzed by principal component analysis. DNA similarities between subspecies coincided with a former taxonomic treatment in the sense that ssp. albicans is the most distantly related to ssp. acaule and ssp. aemulans is distantly related. Subspecies acaule and ssp. punae were indistinguishable. In addition, RFLPs could be used to distinguish groups within subspecies. Subspecies aemulans, confined to Argentina, was divided into two populations, one from the province of La Rioja and the other from the province of Jujuy. In ssp. acaule, some accessions from the southernmost distribution area were clearly distinguishable, while the others varied continuously, showing a geographical cline from Peru to Argentina.Reference to a specific brand or firm name does not constitute endorsement by the US Department of Agriculture over others of similar nature not mentioned     

Anther culture of Solanum genotypes

Anther culture response was examined in five Solanum genotypes. Large genotypic differences exist in response to culture and liquid culture media were found to be superior to agar solidified media systems. Pre-treatment effects on embryoid induction were also investigated and two of the genotypes displayed differential response to temperature stress pretreatment. In general the beneficial effect of charcoal in the media was confirmed. Successful embryoid production and plantlet regeneration was obtained from the wild potato species, Solanum papita. The influence of sucrose concentration on embryoid production was also investigated. Large genotype by sucrose interactions were detected and this was mainly due to the differential response of the tuberosum clones to increasing sucrose concentration when compared with S. papita. Embryoids were produced from this species in media containing 15% sucrose although the optimum concentration of sucrose for embryoid production was 9%. The possible role of anther culture techniques in gene introgression and potato improvement is discussed.     

The Mitochondrial Genome of Xiphinema americanum sensu stricto (Nematoda: Enoplea): Considerable Economization in the Length and Structural Features of Encoded Genes

The complete sequence of the mitochondrial genome of the plant parasitic nematode Xiphinema americanum sensu stricto has been determined. At 12626bp it is the smallest metazoan mitochondrial genome reported to date. Genes are transcribed from both strands. Genes coding for 12 proteins, 2 rRNAs and 17 putative tRNAs (with the tRNA-C, I, N, S1, S2 missing) are predicted from the sequence. The arrangement of genes within the X. americanum mitochondrial genome is unique and includes gene overlaps. Comparisons with the mtDNA of other nematodes show that the small size of the X. americanum mtDNA is due to a combination of factors. The two mitochondrial rRNA genes are considerably smaller than those of other nematodes, with most of the protein encoding and tRNA genes also slightly smaller. In addition, five tRNAs genes are absent, lengthy noncoding regions are not present in the mtDNA, and several gene overlaps are present. [Reviewing Editor: Dr. Yues van de Peer] F. Lamberti: Deceased, 2004     

Electrofusion of protoplasts from Solanum tuberosum, S. nigrum and S. bulbocastanum

Leaf protoplasts of two wild species, Solanum nigrum var. gigantea (S. ngr gig) and S. bulbocastanum Dun. (S. blb), were electrofused with leaf protoplasts of two diploid potato clones, H-8105 and ZEL-1136, respectively, in order to confer the late blight-resistance from the wild species to the cultivated potato. The S. ngr gig mesophyll (+) H-8105 mesophyll combination resulted in regenerants of mostly normal ngr phenotype. Two regenerants from this combination were proved to be true hybrids by RAPD analysis but they rooted poorely in vitro and did not survive the transfer to soil. The S. ngr gig (+) H-8105 fusion combination was also performed with H-8105 cell suspension derived protoplasts enabling an easy identification of interspecific fusants on basis of their intermediate morphology. From the S. ngr gig mesophyll (+) H-8105 cultured cell combination, many abnormal shoots were regenerated. The two lines which survived had normal ngr phenotype but the presence of tuberosum (tbr) genome in those regenerants was not confirmed by RAPD analysis. No plants with tbr phenotype were obtained from both of S. ngr gig (+) H-8105 combinations. On the contrary, when S. blb mesophyll protoplasts were electrofused with ZEL-1136 mesophyll protoplasts, all regenerated plants had tbr phenotype, indicating much lower morphogenetic potential of S. bulbocastanum in comparison with that of S. nigrum var. gigantea. However, the hybridity of those regenerants has not been confirmed by RAPD analysis with two different primers. The efficiency of the applied fusion procedure and analysis of the regenerants is discussed.     

Protoplast-fusion-derived Solanum cybrids: application and phylogenetic limitations

Summary We established interspecific Solanum cybrids in order to study the intrageneric nuclear-organelle compatibility and the introgression of advantageous plasmone-coded breeding traits into potato. Cybridization was performed by the donor-recipient protoplast-fusion procedure. We found that the plastomes of S. chacoense, S. brevidens, and S. etuberosum could be transferred into the cybrids having S. tuberosum nuclear genomes; chondriome components were likewise transferred from the former species into these cybrids. The combination with S. chacoense as organelle donor and potato as recipient resulted in green fertile plants with potato morphology. By using S. etuberosum as an organelle donor and potato as recipient, male-sterile cybrid plants, most of them having pigmentation abnormalities, were obtained. The combination of S. brevidens with potato resulted in palegreen (almost albino) regenerants. The latter albino plantlets had both the chloroplast DNA and the mitochondrial DNA of the donor (S. brevidens) and did not survive the transfer into the greenhouse. An immediately applicative result of this study is the de novo establishment of male-sterile plants in a potato cultivar. Such plants should be useful as seed parents in the production of hybrid, true-potato seeds.     

Allozyme variation in the eggplant,Solanum melongena L. (Solanaceae)

Enzyme electrophoretic studies were made in cultivated Solanum melongena L. (eggplant) and similar wild and weedy forms, several of which have been thought to be different species/taxa. Twenty-nine accessions of S. melongena, 33 accessions of weedy forms (referred to as insanum) and 2 accessions of wild forms (referred to as incanum) were surveyed for 29 isozyme loci. In S. melongena, 22 of the 29 loci were monomorphic, and nearly all of its genes were either also monomorphic or in similar frequencies in insanum and incanum. The results demonstrate that the three taxa have a very close genetic relationship. The high genetic identities between them (0.913–0.967) suggests that they are conspecific even though they include extensive morphological diversity.     

Identification of RipAZ1 as an avirulence determinant of Ralstonia solanacearum in Solanum americanum

Ralstonia solanacearum causes bacterial wilt disease in many plant species. Type III-secreted effectors (T3Es) play crucial roles in bacterial pathogenesis. However, some T3Es are recognized by corresponding disease resistance proteins and activate plant immunity. In this study, we identified the R. solanacearum T3E protein RipAZ1 (Ralstonia injected protein AZ1) as an avirulence determinant in the black nightshade species Solanum americanum. Based on the S. americanum accession-specific avirulence phenotype of R. solanacearum strain Pe_26, 12 candidate avirulence T3Es were selected for further analysis. Among these candidates, only RipAZ1 induced a cell death response when transiently expressed in a bacterial wilt-resistant S. americanum accession. Furthermore, loss of ripAZ1 in the avirulent R. solanacearum strain Pe_26 resulted in acquired virulence. Our analysis of the natural sequence and functional variation of RipAZ1 demonstrated that the naturally occurring C-terminal truncation results in loss of RipAZ1-triggered cell death. We also show that the 213 amino acid central region of RipAZ1 is sufficient to induce cell death in S. americanum. Finally, we show that RipAZ1 may activate defence in host cell cytoplasm. Taken together, our data indicate that the nucleocytoplasmic T3E RipAZ1 confers R. solanacearum avirulence in S. americanum. Few avirulence genes are known in vascular bacterial phytopathogens and ripAZ1 is the first one in R. solanacearum that is recognized in black nightshades. This work thus opens the way for the identification of disease resistance genes responsible for the specific recognition of RipAZ1, which can be a source of resistance against the devastating bacterial wilt disease.     

Successive domestication and evolution of the Andean potatoes as revealed by chloroplast DNA restriction endonuclease analysis

Five chloroplast DNA (ctDNA) types (W, T, C, S, and A) have previously been identified in the Andean tetraploid cultivated potatoes (Solanum tuberosum ssp. andigena) and three types (C, S, and A) in diploid cultivated potatoes (S. stenotomum). In this study, ctDNA types were determined for an additional 35 accessions of S. stenotomum and 97 accessions of putative ancestral wild species (15 of S. brevicaule, 26 of S. bukasovii, 4 of S. candolleanum, 25 of S. canasense, 17 of S. leptophyes, and 10 of S. multidissectum). The first five ctDNA types were also identified in S. stenotomum. The wild species were also polymorphic for ctDNA types except for S. brevicaule, which had only W-type ctDNA. T-type ctDNA was not found in any of the wild species and could have originated from W-type ctDNA after S. stenotomum arose. The other types of ctDNA evolved in wild species. The geographical distribution of each ctDNA type indicated that A-type ctDNA arose in central Peru and T-type ctDNA in the Bolivia-Argentine boundary. It is implied that potatoes were successively domesticated and that, in parallel, several wild species were differentiated from time to time and place to place from the ancestral species complex. Subsequent sexual polyploidization formed a wide ctDNA diversity among the Andean tetraploid potatoes, and selection from them formed the limited ctDNA diversity found in Chilean tetraploid potatoes (ssp. tuberosum).Hawkes' (1990) classification system is tentatively adopted throughout this text. Synonyms indicated by Hawkes (1990) for the species names described by various authors are presented in parentheses.     

Random amplified polymorphic DNA variation in the eggplant,Solanum melongena L. (Solanaceae)

RAPD analysis was carried out on 52 accessions of Solanum melongena (eggplant) and related weedy forms known as insanum. Twenty-two primers amplified 130 fragments. Solanum melongena exhibited 117 of the fragments, all of which were also present in insanum. Insanum displayed an additional 13 fragments not found in S. melongena. Overall, the insanum accessions were more diverse than those of S. melongena. The calculated similarity between them was 0.947. The RAPD results were closely concordant with the results of an electrophoretic isozyme survey performed on the same accessions. The concordance of the results shows that even though S. melongena and insanum are highly diverse morphologically, it is no longer appropriate to distinguish them taxonomically.     

Acrylamide gel electrophoresis of seed proteins from someSolanum (sectionSolanum) species

Polyacrylamide gel electrophoresis was used to investigate the seed proteins of 36 accessions belonging toSolanum sect.Solanum (Solanaceae). These accessions represented 20 species, of four differing ploidy levels, and included infraspecific morphological variants. The resultant band patterns tended to reflect the morphological differences and genetical isolation displayed by many of the species. The most variable band patterns were encountered in the taxa with the greatest infraspecific variation, while many of the more morpho-genetically distinct taxa seemed to have species-specific band patterns.Good matches were found between the band patterns of artificial hybrids, those of their known parents, and mixtures of the parental protein extracts. This illustrates the potential use of such a technique for pinpointing possible genome donors of natural hybrids, and especially of polyploids. These comparative band patterns confirmed experimental work on the origin of the hexaploidS. nigrum from the diploidS. americanum and the tetraploidS. villosum, and also supported the suggestion thatS. nigrum contains two genomes from the diploidS. sarrachoides, but not four genomes of the diploidS. americanum.     

AFLP analysis of the diversity and phylogeny of Lens and its comparison with RAPD analysis

AFLP and RAPD marker techniques have been used to evaluate and study the diversity and phylogeny of 54 lentil accessions representing six populations of cultivated lentil and its wild relatives. Four AFLP primer combinations revealed 23, 25, 52 and 48 AFLPs respectively, which were used to partition variation within and among Lens taxa. The results of AFLP analysis is compared to previous RAPD analysis of the same material. The two methods provide similar conclusions as far as the phylogeny of Lens is concerned. The AFLP technique detected a much higher level of polymorphyism than the RAPD analysis. The use of 148 AFLPs arising from four primer combinations was able to discriminate between genotypes which could not be distinguished using 88 RAPDs. The level of variation detected within the cultivated lentil with AFLP analysis indicates that it may be a more efficient marker technology than RAPD analysis for the construction of genetic linkage maps between carefully chosen cultivated lentil accessions.     

Somatic hybrids between Solanum etuberosum and diploid,tuber bearing Solanum clones

Electrofusion was used to obtain somatic hybrids between Solanum etuberosum (2n=2x=24) and two diploid potato lines. These hybridizations were conducted to determine if haploidxwild species hybrids are better fusion partners than conventional S. tuberosumGp. Tuberosum haploids. Restriction fragment length polymerase (RFLP) analyses of the putative somatic hybrids confirmed that each parental genome was present. The somatic hybrids between S. etuberosum and a haploid S. tuberosum clone, US-W730, were stunted and had curled, purple leaves. In contrast, somatic hybrids between S. etuberosum and a haploidxwild species hybrid (US-W 730 haploidx S. berthaultii), were vigorous and generally tuberized under field conditions. These hybrids were designated as E+BT somatic hybrids. Analyses of 23 E+BT somatic hybrids revealed a statistically significant bias towards the retention of S. etuberosum chloroplasts. Stylar incompatibilities were observed when the E+BT somatic hybrids were used as pollen donors in crosses with S. tuberosum cultivars. Reciprocal crosses did not show this incompatibility. The progeny were vigorous and had improved tuber traits when compared to the maternal E+BT parent. RFLP analyses of three sexual progeny lines confirmed the presence of all 12 S. etuberosum chromosomes. In two of these lines, RFLPs that marked each of the 24 chromosome arms of S. etuberosum were present. However, RFLP markers specific for regions on chromosomes 2, 7, and 11 were missing from the third clone. Because other markers for these chromosomes were present in the progeny line, these results indicated the likelihood of pairing and recombination between S. etuberosum and S. tuberosum chromosomes.