Pairing analysis and in situ Hybridisation reveal autopolyploid-like behaviour in Solanum commersonii × S. tuberosum (potato) interspecific hybrids (original) (raw)
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Agronomy
We applied a genomic in situ hybridization (GISH) to analyze the genomic constitution of and meiotic pairing in interspecific somatic hybrids, and in a wide subset of backcrossing derivatives (BC1–BC5), from three interspecific combinations involving the cultivated potato, Solanum tuberosum (AAAA genome), and three diploid (1 EBN) wild Mexican potato species (genome BB)—S. tarnii, S. pinnatisectum, and S. bulbocastanum. The theoretically expected genomic composition was detected in the somatic hybrids (AAAABB) and in the BC1 progeny (AAAAB), whereas in the subsequent BC2–BC4 generations, the partial loss of alien chromosomes was observed and almost all the BC5 genotypes showed a complete chromosome elimination of wild species. GISH revealed a homoeologous pairing between the chromosomes of the A- and the B-genomes in each of the hybrid progenies. Using GISH, we selected introgression lines with a single chromosome of the wild species in a potato genome background, as well as introgr...
Genome, 1999
Four somatic hybrids derived from a diploid wild species Solanum etuberosum and a diploid tuber-bearing Solanum clone 463-4, together with five BC1 and three BC2 plants, were analyzed by genomic in situ hybridization (GISH). None of the four somatic hybrids had the expected chromosome constitutions, i.e., 24 chromosomes from each fusion parent. Either one chromosome from S. etuberosum or one from the potato parent 463-4 was lost in the hybrids. Three BC1 plants had exactly one set of S. etuberosum chromosomes. The other two BC1 plants either had one extra or one fewer S. etuberosum chromosome, possibly because their somatic hybrid parents had an extra or had lost one S. etuberosum chromosome. The presence of one set, or close to one set, of S. etuberosum chromosomes in all BC1 plants suggests a preferential pairing and segregation of the S. etuberosum chromosomes in the somatic hybrids. Two of the three BC2 plants had 52 chromosomes, deviating significantly from the expected chromos...
Heredity, 1995
Backcross progenies, BC1 and BC2, derived from crossing a hexaploid potato (+) tomato fusion hybrid to tetraploid potato, were monitored for the presence of alien tomato chromosomes. For discriminating the tomato chromosomes from those of potato, both mitotic and meiotic chromosome preparations were labelled differentially through total genomic DNA in situ hybridization (GISH). The presence or absence of individual tomato chromosomes in the BC progeny was identified through RFLP analyses using chromosome-specific DNA probes. The results indicated that the BC 1 plant possessed only nine chromosomes of tomato instead of the expected haploid set of 12. Of the nine persistent tomato chromosomes, there were three pairs that formed bivalents and three singles that formed univalents at meiosis. One of the single chromosomes was strikingly longer as a result of some structural mutation and could easily be identified in the hexaploid parent, the BC1 and in some of the BC2 plants. From the analyses of BC2 progeny there were indications of the presence in the BC1 of tomato chromosomes 1, 3 and 6 in duplicate, and chromosomes 8, 9 and 10 in the haploid condition. The number of tomato chromosomes transmitted to BC2 plants varied from one to six. The results of GISH revealed that a few BC2 plants possessed more tomato chromosomes than those deduced from RFLP analysis. This indicated the presence of some tomato chromosomes in duplicate and others in the haploid condition. The potential value of these genotypes for establishing potato lines with additions and substitutions of tomato chromosomes is discussed.
Theor Appl Genet, 1992
Electrofusion was carried out between mesophyll protoplasts from the transformed diploid S. tuberosum clone 413 (2n = 2x = 24) which contains various genetic markers (hormone autotrophy, opine synthesis, kanamycin resistance,/%glucuronidase activity) and mesophyll protoplasts of a diploid wild-type clone of N. plumbaginifolia (2n = 2x = 20). Hybrid calli were obtained after continuous culture on selection medium containing kanamycin. Parental chromosome numbers, determined at 2 months after fusion, revealed hybrid-specific differences between the individual calli. On the basis of these differences three categories of hybrids were distinguished. Category I hybrids contained between 8 and 24 potato chromosomes and more than 20 N. plumbaginifolia chromosomes; category II hybrids had between I and 20 N. plumbaginifolia chromosomes and more than 24 potato chromosomes; category III hybrids contained diploid or subdiploid numbers of chromosomes from both parents. The hybrids were evenly distributed over the three categories. After a 1-year culture of 24 representative hybrid callus lines on selection medium the karyotype of 10 hybrids remained stable, whereas 8 hybrids showed polyploidization of the genome of one parent, together with no or minor changes of the chromosome numbers of the other parent. Six hybrids showed slight changes in the hybrid karyotype. The elimination of chromosomes of a particular parent was not correlated to their metaphase location. The processes of spontaneous biparental chromosome elimination leading to the production of asymmetric hybrids of different categories are discussed.
Plant Breeding, 1999
Intraspeci_c somatic hybrids have been produced by protoplast fusion in eight combinations involving 09 dihaploids "1n 1x 13# in an attempt to provide new material for potato breeding[ Cytological analy! sis revealed extensive variation in chromosome number\ such as aneu! ploid\ aneusomatic and mixoploid hybrids[ Most of the hybrids represented the expected chromosome number of 37^however\ the frequency of aneuploids reached 49) in some combinations[ Some hybrids carried structurally rearranged chromosomes and exhibited a high frequency of aberrant anaphases[ Isozyme and random ampli_ed polymorphic DNA "RAPD# patterns of the hybrids from the same fusion combination were uniform[ In the _eld\ somatic hybrids showed wide phenotypic variation in 19 morphological characters[ There was a signi_cant correlation between certain leaf characters and the ploidy level\ which may be used to distinguish the tetraploid hybrids from hexaploids and octoploids[ Tuber yield and~owering intensity were highest in tetraploid hybrids "1n 3x 37#[ Eighteen of the 62 hybrids reached higher yields than the standard variety {Adretta|[ Floral devel! opment and fertility were restored in hybrids derived from fusions between non!~owering or sterile dihaploids[
Introgressive Hybridization in Potato Revealed by Novel Cytogenetic and Genomic Technologies
American Journal of Potato Research
Potato is the third most important food crop in the world and is crucial to ensure food security. However, increasing biotic and abiotic stresses jeopardize its stable production. Fortunately, breeders count on a rich pool of wild relatives that provide sources for disease resistance and tolerance to environmental stresses. To use such traits effectively, breeders require tools that facilitate exploration and exploitation of the genetic diversity of potato wild relatives. Introgression programs to incorporate such alien chromatin into the crop have so far relied on cytogenetic and genetic studies to tap desired traits from these wild resources. The available genetic and cytogenetic tools, supplemented with more recent genomic technologies, can assist in the use of potato relatives in pre-breeding. This information can also facilitate cisgenesis and genome editing to improve potato cultivars. Despite the abundant and rapidly growing genomic information of potato, that of its wild relatives is still limited. Resumen La papa es el tercer alimento más importante en el mundo y es crucial para garantizar la seguridad alimentaria. No obstante, el aumento de los factores adversos bióticos y abióticos pone en riesgo la estabilidad de la producción. Afortunadamente, los mejoradores cuentan con rico acervo de parientes silvestres que suministran fuentes de resistencia a enfermedades y tolerancia a factores ambientales adversos. Para utilizar tales caracteres efectivamente, los mejoradores requieren de herramientas que faciliten la exploración y explotación de la diversidad genética de los parientes silvestres de la papa. Los programas de introgresión para incorporar tal cromatina ajena al cultivo hasta ahora han recurrido a estudios citogenéticos y genéticos para captar caracteres deseables de esas fuentes silvestres. Las herramientas genéticas y citogenéticas disponibles, suplementadas con tecnologías genómicas más recientes, pueden asistir en el uso de los parientes de la papa en pre-mejoramiento. Esta información también puede facilitar la cisgénesis y la edición genómica para mejorar las variedades de papa. A pesar del abundante y rápido crecimiento de la información genómica de la papa, la de los parientes silvestres es aún limitada.
Genome, 2016
A major bottleneck to introgressive hybridization is the lack of genome collinearity between the donor (alien) genome and the recipient crop genome. Structural differences between the homeologs may create unbalanced segregation of chromosomes or cause linkage drag. To assess large-scale collinearity between potato and two of its wild relatives (Solanum commersonii and Solanum chacoense), we used BAC-FISH mapping of sequences with known positions on the RH potato map. BAC probes could successfully be hybridized to the S. commersonii and S. chachoense pachytene chromosomes, confirming their correspondence with linkage groups in RH potato. Our study shows that the order of BAC signals is conserved. Distances between BAC signals were quantified and compared; some differences found suggest either small-scale rearrangements or reduction/amplification of repeats. We conclude that S. commersonii and S. chacoense are collinear with cultivated Solanum tuberosum on the whole chromosome scale, ...
TAG Theoretical and Applied Genetics, 2002
In order to assess the potential for interspecific recombination between the cultivated Solanum tuberosum (tbr) and the sexually isolated wild species Solanum commersonii (cmm), genetic analysis of a F 2 progeny obtained by selfing one tetraploid cmm (+) tbr somatic hybrid was performed through molecular markers. For this purpose, the extent of disomic and/or tetrasomic inheritance of species-specific RAPD and AFLP markers was determined by following their segregation in a 90-genotype progeny, and testing all the possible segregation ratios in a selfed tetraploid progeny. The RAPD analysis performed using 16 primers revealed that the cmmspecific RAPDs were mainly (93.7%) duplex markers and were equally distributed between loci with a disomic (46.7%) and tetrasomic (53.3%) inheritance. The AFLP analysis led to the identification of 272 (58%) informative AFLPs, which were either cmm-or tbr-specific markers. About 63% of cmm-specific AFLPs were duplex loci, most of which (92.6%) were inherited as tetrasomic loci. As regards the tbr-specific AFLPs, the percentage of simplex loci (52.9%) was higher than that of duplex loci (32.6%), and among the latter most (88.5%) were inherited as tetrasomic loci. Overall, 130 duplex markers were found, of which 53.1% were cmm-specific and 46.9% were tbr-specific. Out of 130 markers, 18 (13.8%) were inherited as disomic, and 112 (86.2%) as tetrasomic, loci. This implies that the majority of duplex markers were located on chromosomes which at meiosis tend to randomly pair as bivalents or to form tetravalents. The total number of simplex loci was 119, and most of them (82.3%) were tbr-specific loci. In some cases the observed segregation ratios even allowed us to clearly determine whether a random chromosome or chromatid segregation was detected. This was the case of three cmm-specific RAPDs, 19 cmm-and 25 tbr-specific AFLPs, which fit a 20.8:1 or 2.5:1 ratio, both cases for which a clear random chromatid segregation can be assumed, since they represent the limit of segregation expected when the distance between the locus and the centromere always leads to a cross-over event. The percentage of ascertained crossing-over events was around 37% out of the tetrasomically inherited loci clearly identified (128 loci), a value indicating that the flow of genes from the sexually isolated S. commersonii to the cultivated potato is possible, for at least a large proportion of genes.
Genome, 1999
BC 1 pentaploid to near-pentaploid Solanum commersonii-S. tuberosum genotypes obtained from 3x × 4x crosses have been used for cytological and molecular studies on chromosome pairing and meiotic recombination. Microsporogenesis analysis at diakinesis revealed that chromosomes had a tendency to pair as bivalents, though multivalents were also observed in many cells. Meiosis resulted in a high production of tetrads and pollen stainability was high, ranging from 34.5% to 92.1%. DNA from S. commersonii and S. tuberosum was amplified with 87 decameric primers, resulting in the identification of 26 S. commersonii-specific RAPDs. The analysis of these RAPDs in BC 1 genotypes showed that a number of commersonii-specific markers was present in all BC 1 genotypes. On the other hand, markers which were missing in one or more of the BC 1 genotypes suggested that in some cases homoeologous pairing occurred. Two linked markers were transmitted together in all of the BC 1 genotypes except two. This provided evidence that a recombination event between these markers occurred during megasporogenesis of their triploid parents. The possibility of demonstrating other recombination events is discussed.
Interspecific Hybridization in Potato by Unilateral Sexual Polyploidization
XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on New Developments in Plant Genetics and Breeding, 2012
This work was carried out in the Laboratory of Plant Biotechnology at University of Passo Fundo, in South Brazil. The objective of these experiments was to test, for local condition, the hybridization technique strategy by sexual unilateral polyploidization in potato in order to transfer genes from wild diploid into the tetraploid cultivated species. Initially, the temperature effect on the occurrence of unreduced (2n) pollen grains in two diploid clones at temperature of 10, 15, 20, 25, 30 and 35°C was evaluated. The highest frequency of unreduced pollen grains was observed in temperatures of 15°C with an average of 30.7% for one clone and 7.6% for the other. Both clones were used as male parents in crosses with tetraploid cultivars. A total of 109 crosses were performed, and in 14 of them, 2,4-D was applied after pollinations. After pollination, three fruits were obtained from 14 flowers that were treated with 2,4D. However, only one of them was fertile, producing five plants, which presented morphological traits from both parents, eliminating the self-pollination hypothesis. The number of mitotic chromosomes of F 1 plants was 48. This tetraploid ploidy level shows that the tetraploid cultivar oosfere was fertilized by the unreduced pollen of diploid species. This indicated the overcoming of a critical restriction for the genes transference between plants with different ploidy levels had occurred. Although this strategy needs to be optimized, this work shows the possibility of using non reduced pollen grain as a bridge to transfer desirable traits from wild gene pool to the cultivated one under our conditions. This enlarges the genetic variability of the crop, increasing the potential of developing new potato cultivars having disease resistance, good eating quality and superior agronomic traits.