The novel, major locus Rpi-phu1 for late blight resistance maps to potato chromosome IX and is not correlated with long vegetation period

Despite the long history of breeding potatoes resistant to Phytophthora infestans, this oomycete is still economically the most important pathogen of potato worldwide. The correlation of high levels of resistance to late blight with a long vegetation period is one of the bottlenecks for progress in breeding resistant cultivars of various maturity types. Solanum phureja was identified as a source of effective late blight resistance, which was transferred to the cultivated gene pool by interspecific crosses with dihaploids of Solanum tuberosum. A novel major resistance locus, Rpi-phu1, derived most likely from S. phureja and conferring broad-spectrum resistance to late blight, was mapped to potato chromosome IX, 6.4 cM proximal to the marker GP94. Rpi-phu1 was highly effective in detached leaflet, tuber slice and whole tuber tests during 5 years of quantitative phenotypic assessment. The resistance did not show significant correlation with vegetation period length. Our findings provide a well-characterized new source of resistance for breeding early and resistant-to-P. infestans potatoes.Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at .     

Application of somatic hybrids between dihaploids of potato Solanum tuberosum L. and wild diploid species from Mexico in breeding: Generation and backcrossing of dihaploids of somatic hybrids

The efficiency of an original approach to involvement of the valuable genetic pool of wild diploid potato species from Mexico is estimated. The essence of this method is in generation of dihaploids (2n = 2x = 24) of tetraploid somatic hybrids (2n = 4x = 48) followed by backcrossing with dihaploids of Solanum tuberosum. A haploid producer, S. phureja IvP35, was used to generate ten dihaploids of S. tuberosum + S. pinnatisectum, all of which crossed with fertile S. tuberosum dihaploids and developed plump viable seeds. This gives the possibility of an efficient introgression of the genes valuable for breeding from wild species to the bred plants at a diploid level, which has several advantages compared with the corresponding procedure at a tetraploid level. A part of the dihaploids produced was compatible (the pollen tubes reached the ovary) with diploid and tetraploid forms of S. pinnatisectum; however, no viable seeds were developed. The attempt to generate the dihaploids of S. tuberosum + S. bulbocastanum somatic hydrides using the haploid producer S. phureja IvP35 was unsuccessful.     

Variation patterns of parthenogenetic plants derived from “unreduced” embryo-sacs of Solanum tuberosum subspecies andigena (Juz. et Buk.) Hawkes

Summary Parthenogenetic seed induction was performed on one clone of Solanum tuberosum subspecies andigena (2n=4x=48) using S. phureja (2n=2x=24) marker inducer clones. The parthenogenetic population when grown was found to contain both diploid and tetraploid individuals presumably arising from reduced and unreduced gametes, respectively. Variation patterns in the diploid and tetraploid sub-populations, as well as a population obtained by selfing the parental clone, were compared to try and elucidate the origin of the tetraploid parthenotes. From the results of this one generation it appeared that the tetraploid parthenogenetic plants had been produced by a mechanism equivalent to second division restitution (SDR).     

Resistance to late blight in Solanum bulbocastanum is mapped to chromosome 8

Somatic hybrids between potato and Solanum bulbocastanum, a wild diploid (2n=2x=24) Mexican species, are highly resistant to late blight, caused by Phytophthora infestans. Both randomly amplified polymorphic DNA (RAPD) and restriction fragment length polymorphism (RFLP) markers that are closely linked to the resistance have been noted by analysis of three different backcross-2 populations derived from two different somatic hybrids. With reference to previously published potato and tomato maps, resistance appears to be on the long arm of chromosome 8 and is flanked by RFLP markers CP53 and CT64. In a population of BC₂ plants derived from a cross between the BC₁ line J10lK6 [(S. tuberosum PI 203900+S. bulbocastanum PI 243510) ×Katahdin)]×Atlantic, late blight resistance cosegregated with RFLP marker CT88 and RAPD marker OPG02–625. Received: 26 November 1999 / Accepted: 22 December 1999     

Exploitation of colinear relationships between the genomes of<Emphasis Type="Italic"> Lotus japonicus</Emphasis>,<Emphasis Type="Italic"> Pisum sativum</Emphasis> and<Emphasis Type="Italic"> Arabidopsis thaliana</Emphasis>, for positional cloning of a legume symbiosis gene

The Lotus japonicus LjSYM2 gene, and the Pisum sativum orthologue PsSYM19, are required for the formation of nitrogen-fixing root nodules and arbuscular mycorrhiza. Here we describe the map-based cloning procedure leading to the isolation of both genes. Marker information from a classical AFLP marker-screen in Lotus was integrated with a comparative genomics approach, utilizing Arabidopsis genome sequence information and the pea genetic map. A network of gene-based markers linked in all three species was identified, suggesting local colinearity in the region around LjSYM2/PsSYM19. The closest AFLP marker was located just over 200 kb from the LjSYM2 gene, the marker SHMT, which was converted from a marker on the pea map, was only 7.9 kb away. The LjSYM2/PsSYM19 region corresponds to two duplicated segments of the Arabidopsis chromosomes AtII and AtIV. Lotus homologues of Arabidopsis genes within these segments were mapped to three clusters on LjI, LjII and LjVI, suggesting that during evolution the genomic segment surrounding LjSYM2 has been subjected to duplication events. However, one marker, AUX-1, was identified based on colinearity between Lotus and Arabidopsis that mapped in physical proximity of the LjSym2 gene.Communicated by J.S. Heslop-Harrison     

Introgression of resistance to root-knot nematodes from wild Central American Solanum species into S. tuberosum ssp. tuberosum

 Crossing experiments were conducted to introduce resistance to the root-knot nematodes, Meloidogyne chitwoodi and M. fallax, from various polyploid Central American Solanum spp. into the cultivated potato, S. tuberosum ssp. tuberosum. The most effort was put into producing tetraploid hybrids through inter-EBN (Endosperm Balance Number) crosses. From the crosses of tetraploid S. tuberosum (4 EBN) with tetraploid S. stoloniferum and S. fendleri (both 2 EBN), few seeds were derived that led to viable plants. In vitro culture of immature seeds also yielded several hybrid plants. From crosses of diploid S. tuberosum (2 EBN) with hexaploid S. hougasii (4 EBN) four hybrids were obtained through in vitro culture. Backcrosses were made with selected hybrids and a variable number of seeds was produced depending on the hybrid genotype. The successful introgression of resistance into backcross populations is shown. A scheme is presented for the introgression of traits at a tetraploid level from allotetraploid Solanum species into autotetraploid S. tuberosum through sexual crosses. The relevance of EBN for potato breeding is discussed. Received: 25 November 1996 / Accepted: 14 February 1997     

Mapping genes for resistance to<Emphasis Type="Italic"> Verticillium albo-atrum</Emphasis> in tetraploid and diploid potato populations using haplotype association tests and genetic linkage analysis

Verticillium wilt disease of potato is caused predominantly by Verticillium albo-atrum and V. dahliae. StVe1 —a putative QTL for resistance against V. dahliae —was previously mapped to potato chromosome 9. To develop allele-specific, SNP-based markers within the locus, the StVe1 fragment from a set of 30 North American potato cultivars was analyzed. Three distinct and highly diverse haplotypes can be distinguished at the StVe1 locus. These were detected in 97%, 33%, and 10% of the cultivars analyzed. We tested for haplotype association and for genetic linkage between the StVe1 haplotypes and resistance of tetraploid potato to V. albo-atrum. Moreover, field resistance was assessed in diploid populations with known molecular linkage maps in order to identify novel QTLs. Resistance QTLs against V. albo-atrum were detected on four chromosomes (2, 6, 9, and 12) at the diploid level, with one QTL on chromosome 2 contributing over 40% to the total phenotypic variation of the trait. At the tetraploid level, a significant association between the StVe1-839-C haplotype and susceptibility to the disease was detected, suggesting that resistance-related genes directed against V. albo-atrum and V. dahliae are located in the same genomic region of chromosome 9. However, on the basis of the present analysis, we cannot determine whether these genes are closely linked or if a single gene provides resistance against both Verticillium species. To assess the usefulness of the StVe1-839-C haplotype for marker-assisted selection, we subjected the resistance data to Bayesian analysis, and calculated positive (0.65) and negative (0.75) predictive values, and overall predictive accuracy (0.72). Our results indicate that tagging of additional genes for resistance to Verticillium with molecular markers will be required for efficient marker-assisted selection.Communicated by M.-A. Grandbastien     

Novel somatic hybrids (Solanum tuberosum L. + Solanum tarnii) and their fertile BC1 progenies express extreme resistance to potato virus Y and late blight

Solanum tarnii, a wild diploid, tuber-bearing Mexican species belonging to the series Pinnatisecta is highly resistant to Potato virus Y (PVY) and Colorado potato beetle and shows a strong hypersensitive reaction to Phytophthora infestans. Therefore, it could be a potential source of resistance to pathogens for potato breeders. S. tarnii (2n = 2x = 24) is reproductively isolated from tetraploid Solanum tuberosum and hence difficult to include in potato breeding programmes. In this study, interspecific somatic hybrids were produced for the first time by protoplast electrofusion of the cells of potato cv. Delikat (Solanum tuberosum L.) and Solanum tarnii. The hybrid nature of the regenerants was confirmed by simple sequence repeat (SSR) and amplified fragment length polymorphism (AFLP) markers and by morphological analysis and flow cytometry. Selected somatic hybrids were successfully backcrossed with cv. Delikat. Parental lines, primary somatic hybrids and BC₁ progeny were assessed for resistance to PVY by mechanical inoculation, grafting and exposure to viruliferous aphid vectors in the field, and resistance to late blight (P. infestans) by detached leaflet and whole tuber tests. The somatic hybrids showed no symptoms of viral infection and most of them displayed high levels of resistance to foliage blight. The BC₁ progenies were highly resistant to PVY and a few were resistant to foliage blight. Selected hybrids and BC₁ clones were evaluated in the field for tuber quality and tuber yield. Some BC₁ clones produced yields of good quality tubers. The results confirm that both the resistance to PVY and to late blight of S. tarnii is expressed in somatic hybrids, and PVY resistance is transferred to BC₁ progeny, whereas blight resistance is harder to transfer. Somatic hybridization again proved to be a valuable tool for producing pre-breeding material with increased genetic diversity.     

Genetic relationships of tetraploid<Emphasis Type="Italic"> Elymus</Emphasis> species and their genomic donor species inferred from polymerase chain reaction-restriction length polymorphism analysis of chloroplast gene regions

The genetic relationships of 38 individuals from 13 Elymus tetraploid species, two Pseudoroegneria species and one Hordeum species were examined using polymerase chain reaction-restriction length polymorphism analysis of chloroplast gene regions. The 13 Elymus species contain SH and SY genomes with either a single spikelet or multiple spikelets per rachis node. The Pseudoroegneria and Hordeum species contain an S genome with single spikelet per rachis node and an H genome with multiple spikelets per rachis node, respectively. Four chloroplast gene regions, trnD-trnT intron, trnK [tRNA-Lys (UUU) exon1]–trnK [tRNA-Lys (UUU) exon2], trnC-trnD, and rbcL were amplified with specific primers and subsequently digested with up to 16 different restriction enzymes. Interspecific variation was detected in the four regions. A dendrogram based on similarity matrices using the unweighted pair group method with arithmetic average algorithm separated the 38 individuals into two distinct groups: the Elymus and Pseudoroegneria species as one group and Horduem as a second group. This result corresponded well with previous findings, and strongly suggested that a Pseudoroegneria species is the maternal donor to tetraploid Elymus species. Unlike previous studies using nuclear genes, the chloroplast DNA used in this study could not clearly separate the SY-genome species from SH-genome species. No clear separation between the species with a single spikelet per rachis node and the species with multiple spikelets per rachis node was found. Intra-specific variation was detected for the species studied. These observations provide molecular evidence for the highly diverse nature of the Elymus gene pool based on morphological characteristics.Communicated by H.F. Linskens     

CENTRORADIALIS/TERMINAL FLOWER 1 gene homolog is conserved inN. tabacum, a determinate inflorescence plant

A mutation in theCENTRORADIALIS (CEN) gene ofAntirrhinum and in theTERMINAL FLOWER 1 (TFL1) gene ofArabidopsis causes their indeterminate inflorescence to determinate. We clonedCEN/TFL1 homologs fromNicotiana tabacum, the wild-type of which has a determinate inflorescence. TheCEN gene was expressed in the inflorescnece meristem and kept its inflorescence meristem identity, whereas the tobacco homolog (NCH) was expressed at a low level throughout the plant’s development. AlthoughCEN andNCH are highly homologous genes, they may have been recruited to different developmental functions during their evolution. TwoNCH genes are derived from amphidiploidN. tabacum, but both of them hybridized with its diploid parents,N. sylvestris andN. tomentosiformis. Southern blotting, and the genomic organization ofTFL1 inArabidopsis revealed that anotherCEN homolog exists in the genome ofArabidopsis. These results suggest that there are two copies of theCEN homolog per diploid plant. The extended abstract of a paper presented at the 13th International Symposium in Conjugation with Award of the International Prize for Biology “Frontier of Plant Biology” These two authors contributed to this work equally.     

Tagging QTLs for late blight resistance and plant maturity from diploid wild relatives in a cultivated potato (Solanum tuberosum) background

Phytophthora infestans causes an economically important disease of potato called late blight. The epidemic is controlled chemically but resistant potatoes can become an environment-friendly and financially justified alternative solution. The use of diploid Solanum tuberosum derived from European tetraploid cultivars enabled the introgression of novel genes encoding foliage resistance and tuber resistance from other species into the modern cultivated potato gene pool. This study evaluated the resistance of the obtained hybrids, its quality, expression in leaflets and tubers and its relation to the length of vegetation period. We also identified genetic loci involved in late blight resistance and the length of vegetation period. A family of 156 individuals segregating for resistance to late blight was assessed by three laboratory methods: detached leaflet, tuber slice and whole tuber test, repeatedly over 5 years. Length of vegetation period was estimated by a field test over 2 years. The phenotypic distributions of all traits were close to normal. Using sequence-specific PCR markers of known chromosomal position on the potato genetic map, six quantitative trait loci (QTLs) for resistance and length of vegetation period were identified. The most significant and robust QTL were located on chromosomes III (explaining 17.3% of variance observed in whole tuber tests), IV (15.5% of variance observed in slice tests), X (15.6% of variance observed in leaflet tests) and V (19.9% of variance observed in length of vegetation period). Genetic characterization of these novel resistance sources can be valuable for potato breeders and the knowledge that the most prominent QTLs for resistance and vegetation period length do not overlap in this material is promising with respect to breeding early potatoes resistant to P. infestans. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Allozyme variability and phylogenetic relationships in the cultivated potato (Solanum tuberosum) and related species

Gene frequencies at 13 isozyme loci were determined in three South American taxa of cultivated potatoes [the diploid group (gp.) Stenotomum, the diploid subgroups (subgp.) Goniocalyx, and the tetraploid gp. Andigena ofS. tuberosum], in the diploid weed speciesS. sparsipilum, and in most of the main cultivars now raised in the Northern Hemisphere (the tetraploid gp. Tuberosum ofS. tuberosum). High levels of genetic variability (mean number of alleles per locus, percentage of polymorphic loci, and mean heterozygosity) were detected, being higher in tetraploid potatoes. An equilibrium among the evolutionary factors which increase genetic variability and artificial selection for maximum yield would explain the high uniformity of heterozygosity values we observed in both Andigena (0.36 ± 0.02) and Tuberosum (0.38 ± 0.01) cultivars.—The low value of genetic distance (D = 0.044) between Stenotomum and Goniocalyx does not support the status of species forS. goniocalyx.—In most isozyme loci, the electromorphs of gp. Andigena were a combination of those found in both gp. Stenotomum andS. sparsipilum, suggesting an amphidiploid origin of gp. Andigena from that two diploid taxa. The presence in Andigena of unique electromorphs, which were lacking in both gp. Stenotomum andS. sparsipilum, suggests that other diploid species could be also implied in the origin of tetraploid Andean potatoes. Furthermore, since Andigena were more related to Stenotomum (D = 0.052) than toS. sparsipilum (D = 0.241), the autopolyploidization of Stenotomum individuals and the subsequent hybridization with gp. Andigena may also have occurred. Thus, our study suggests a multiple origin (amphidiploidy, autoploidy, and hybridization at tetraploid level) of gp. Andigena.—Most of the electromorphs of gp. Tuberosum were also found in gp. Andigena; both the direct derivation of that group from the Andean tetraploid potatoes and the repeated introgression provided by breeding programmes could explain this result. However, the allele c of Pgm-B, present in 30 out of 76 Tuberosum cultivars from Northern Hemisphere as well as in 3 Chilean Tuberosum cultivars, lacks in the 258 Andigena genotypes sampled, suggesting that Chilean germplasm could have taken part in the origin of at least the 39% of the potato cultivars from Europe and North America analyzed here.—The distanceWagner procedure provides an estimate of a 30% of heterogeneity in the evolutionary divergence shown by different groups of cultivated potatoes. Diploid groups show a higher (22.5%) evolutionary rate than tetraploids, which can be attributed to both tetrasomic inheritance and facultative autofecundation that exists in Andigena and Tuberosum groups. Thus, artificial selection acting since 10000 years has not resulted in a higher rate of molecular evolution at the isozyme level in the tetraploids.     

AFLP analysis to assess genomic stability in Solanum regenerants derived from wild and cultivated species

The cultivated potato as well as its tuber-bearing relatives are considered model plants for cell and tissue culture, and therefore for exploiting the genetic variation induced by in vitro culture. The association between molecular stability and tissue culture in different genetic backgrounds and ploidy levels has already been explored. However, it still remains to be ascertained whether somaclonal variation differs between callus-derived chromosome-doubled and undoubled regenerants. Our research aimed at investigating, through amplified fragment length polymorphism (AFLP) markers, the genetic changes in marker-banding patterns of diploid and tetraploid regenerants obtained from one clone each of Solanum bulbocastanum Dunal and S. cardiophyllum Lindl (both 2n = 2x = 24) and tetraploids from cultivated S. tuberosum L. (2n = 4x = 48). Pairwise comparisons between the banding patterns of regenerants and parents allowed detecting considerable changes associated to in vitro culture both at diploid and tetraploid level. The percentages of polymorphic bands between diploid and tetraploid regenerants were, respectively, 57 and 69% in S. bulbocastanum and 58 and 63% in S. cardiophyllum. On average, the frequencies of lost parental fragments in regenerants were significantly higher than novel bands both in S. bulbocastanum (48 vs. 22%) and S. tuberosum (36 vs. 18%) regenerants. By contrast, in S. cardiophyllum, a similar incidence of the two events was detected (32 vs. 29%). Our results revealed that structural changes after tissue culture process strongly affected the genome of the species studied, but diploid and tetraploids regenerated plants responded equally.     

The origin of the cultivated tetraploid potato based on chloroplast DNA

Summary By using restriction enzyme analysis of chloroplast DNA, a geographical cline from the Andean region to coastal Chile was found for the tetraploid potato (Solanum tuberosum). This supports the Andean origin of Chilean ssp. tuberosum. One of the relic cultivars of the early introduction of potato to Europe had ssp. andigena type chloroplast DNA. Its derivatives were largely lost in the mid-19th century due to the late blight epidemic and were replaced by ssp. tuberosum originally introduced from Chile. Therefore, the present common potato has the same type chloroplast DNA as Chilean ssp. tuberosum.     

Expression of wild-type GBSS transgenes in the off-spring of partially and fully complementedamylose-free transformants of potato

Theamylose-free (amf) potato mutant can easily be complemented through introduction of the wild-type gene coding for granule-bound starch synthase (GBSS). After iodine staining the starch of theamf mutant is red whereas that of the wild type and the complementedamf mutant is blue. The level of complementation of selected transformants and their sexual off-spring after backcrossing withamf was investigated using sporophytic tuber cells and gametophytic microspore cells. Two diploid and two tetraploid transformants with full complementation demonstrated the expected segregation patterns of 1:1 (one active insert) or 3:1 (two independently segregating active inserts) in the microspores and in the F1 offspring based on staining of tubers. All expected genotypes in the F1 generation were found, based on microspore segregation patterns of the individual F1 plants. Two transformants with partial complementation (mixed phenotypes) were investigated. One of them, B1, was tetraploid and duplex for the GBSS insert, which had originated through mitotic doubling of the transformed diploid cells. In the F1 generation three phenotypic classes were found:amf, fully complemented and partially complemented. The latter two classes exist independently of a simplex or duplex gene status. The second transformant with partial complementation, B10, appeared to have a complex molecular composition. One cluster of five transgenes caused the partial complementation. Fully and partially complemented phenotypic classes were found after crossing B10 with theamf mutant. Indications were found that the ploidy level of the tissue in which the genes were introduced and expressed played an important role. Firstly, partial complementation was found after transformation of the diploid and not of the tetraploidamf genotypes. Secondly, the level of complementation was higher in tissue with lower ploidy levels, as illustrated by the colour of the starch inin vitro tubers (2x–4x cells) versus field-grown tubers (16x–64x).     

A map of barley chromosome 2 using isozymic and morphological markers

The F₂ progeny of a cross between a chromosome 2 multiple marker stock and an adapted cultivar of barley were analyzed for four morphological markers and electrophoretic patterns of eight leaf isozymes. TheIdh-2 locus was linked to thePer-5 locus (27.96±5.07 cM) and to thee locus (10.26±3.13 cM). Also, thePer-5 ande loci were located on the short arm of chromosome 2. In additionIdh-2 was also located on barley chromosome 2 and was linked to thev locus (13.18±3.56 cM), which is located on the long arm of chromosome 2. Two other marker genes,li andwst,,B, were linked (26.50±5.24 cM) on chromosome 2 but segregate independently of the other loci evaluated. This project was supported by funds from the U.S.-Spain Joint Committee for Scientific and Technological Cooperation.     

Relationships among genetic distance,forage yield and heterozygosity in isogenic diploid and tetraploid alfalfa populations

Isogenic diploid and tetraploid alfalfa (Medicago sativa L.) was studied with molecular markers to help understand why diploid performance and breeding behavior does not always predict that of tetraploids. In a previous study of partially heterozygous alfalfa genotypes, we detected a low correlation between yields of isogenic diploid (2x) and tetraploid (4x) single-cross progenies, and genetic distances were more highly correlated with yields of tetraploids than diploids. These differences may be related to the level of RFLP heterozygosity expected among progenies derived from heterozygous parents at the two ploidy levels. The objectives of this study were to determine the relationships among genetic distance, forage yield and heterozygosity in isogenic 2 x and 4 x alfalfa populations. Four diploid genotypes were chromosome doubled to produce corresponding isogenic autotetraploids, and these genotypes were mated in 4 × 4 diallels to produce 6 single-cross families at each ploidy level for field evaluation. Allele compositions of parents were determined at 33 RFLP loci by monitoring segregation of homologous restriction fragments among individuals within progenies, and these were used to estimate RFLP heterozygosity levels for all single-cross progenies at both ploidy levels. RFLP heterozygosity rankings were identical between progenies of isogenic diploid and tetraploid parents; but significant associations (P < 0.05) between estimated heterozygosity levels and forage yield were detected only at the tetraploid level. Since tetraploid families were nearly 25% more heterozygous than the corresponding diploid families, inconsistencies in the association between molecular marker diversity and forage yields of isogenic 2 x and 4 x single crosses may be due to recessive alleles that are expressed in diploids but masked in tetraploids. The gene action involved in heterosis may be the same at both ploidy levels; however, tetraploids benefit from greater complementary gene interactions than are possible for equivalent diploids. Present address: AgResearch Grasslands, New Zealand Pastoral Agriculture Research Institute, Palmerston North, New Zealand     

Mapping and marker-assisted selection for a gene for extreme resistance to potato virus Y

The chromosomal location of the major gene Ry _adg controlling extreme resistance to potato virus Y (PVY) in Solanum tuberosum subsp. andigena was identified by RFLP analysis of a diploid potato population. A total of 64 tomato and potato RFLP markers were screened with the bulked segregant analysis (BSA) on segregants extremely resistant, hypersensitive or susceptible to PVY. Four markers TG508, GP125, CD17 and CT168 at the proximal end of chromosome XI showed close linkage with extremely resistant phenotypes. TG508 was identified as the closest marker linked with the Ry _adg locus with the maximum map distance estimated as 2.0 cM. The 4 markers linked with the Ry _adg locus were tested on independent tetraploid and diploid potato clones and were subsequently found useful for marker-assisted selection for plants containing Ry _adg . Received: 5 July 1996 / Accepted: 19 July 1996     

Plant regeneration from in vitro culture of anthers of Solanum chacoense Bitt. and interspecific diploid hybrids S. tuberosum L. x S. chacoense Bitt.

Summary Production of plants from cultured anthers of Solanum chacoense clone IP 33, of its interspecific diploid hybrids with S. tuberosum clones IP 354 and IP 372, and of a complex Solanum hybrid containing in its genome S. ajanhuiri is reported. Genotypic differences were found to influence both the induction phase and the regeneration process. Hybrids derived from clone IP 354 of S. tuberosum were much more responsive in culture than hybrids from clone IP 372. Altogether, 507 plants were regenerated and 309 were cytologically analyzed. Of these, 52% were haploid, 47% diploid and 1% mixoploid or tetraploid. A number of diploid plants probably originated from unreduced microspores and some genetic consequences of this event are discussed.