In Situ Localization of Parental Genomes in a Wide Hybrid

In situ hybridization enabled DNA originating from the two parentalgenomes to be distinguished in plant hybrids. A probe of biotinylatedtotal genomic DNA from Secale africanum labelled the chromosomesof S. africanum origin but not those from Hordeum chilense inroot-tip chromosome spreads of the sexual hybrid between thetwo species. Hybridization of total genomic DNA from S. africanumto DNA on filters (dot blots) confirmed the distinction betweenDNA from Hordeum and Secale. The total genomic probe hybridizedto the whole length of the chromosomes from S. africanum remarkablyuniformly, labelling both euchromatin and heterochromatin, exceptat the centromeric region. The probe binding was visualizedas a yellow colour by the fluorescein-coupled detection systemwhich contrasted with the red fluorescing counterstain of theunlabelled chromatin. The chromosomes originating from bothparents could be seen and distinguished as red and yellow fluorescenceat all stages of the cell cycle. At interphase and prophase,the chromatin originating from the two parental genomes didnot mix. Chromosomes or groups of chromosomes occupied distinctdomains and also tended to be arranged in a Rabl configurationwith the centromeres clustered at one end of the nucleus. Wepropose calling the technique using total genomic DNA as a probe‘genomic in situ hybridization.’ Hordeum chilense, Secale africanum, hybrids, genomic in situ hybridization, DNA, repetitive sequences, chromosomes, chromosome disposition, nuclear order     

Discrimination between closely related Triticeae species using genomic DNA as a probe

Summary Labelled total genomic DNA was used as a probe in combination with blocking DNA to discriminate between taxonomically closely related species in the genera Hordeum and Secale. Discrimination was possible both by Southern hybridization to size-fractionated restriction enzyme digests of genomic DNA and by in situ hybridization to chromosome preparations. To distinguish between two species (e.g. H. vulgare and H. bulbosum), genomic DNA from one species was used as the labelled probe, while unlabelled DNA from the other species was applied at a much higher concentration as a block. The blocking DNA presumably hybridized to sequences in common between the block and the labelled probe, and between the block and DNA sequences on the membrane or chromosomes in situ. If so, mainly species-specific sequences would remain as sites for probe hybridization. These species-specific sequences are dispersed and represent a substantial proportion of the genome (unlike many cloned, species-specific sequences). Consequently, rapid nonradioactive methods detected probe hybridization sites satisfactorily. The method was able to confirm the parentage of hybrid plants. It has potentially wide application in plant breeding for the detection of alien DNA transfer, and it can be easily adapted to many species.     

Genomic Origin and Organization of the Hybrid Poa jemtlandica(Poaceae) Verified by Genomic In Situ Hybridization and Chloroplast DNA Sequences

Chloroplast DNA sequencing and genomic in situ hybridization(GISH) were used to investigate the genomic origin and organizationof the alpine grass Poa jemtlandica. Using genomic probes ofP. alpina and P. flexuosa, GISH clearly distinguished betweenthese two putative parental genomes and thus confirmed the hybridnature of P. jemtlandica. The chloroplast trn L intron and trnL–trn F intergenic spacer (IGS) sequence genotypes ofP. flexuosa and P. jemtlandica were 100% identical but differedfrom those of P. alpina by a total of ten or 11 nucleotide substitutionsand six indels over 866 aligned positions, identifying P. flexuosaas the maternal parent of the P. jemtlandica population studiedhere and supporting a relatively recent origin of the hybrid.GISH revealed the presence of intergenomic translocations inthe hybrid genome, indicating that the two parental genomeshave undergone some rearrangements following hybridization.It is likely that some of these chromosome changes took placesoon after hybridization in order to overcome the adverse interactionsbetween the nuclear and the cytoplasmic genomes and to facilitatethe successful establishment of the newly formed hybrid. Thepresence of intergenomic chromosome changes may play an importantrole in the evolution of natural hybrids and the establishmentof new evolutionary lineages. Copyright 2000 Annals of BotanyCompany Natural hybridization, genome origin, intergenomic translocations, GISH, chloroplast DNA sequences, Poa jemtlandica     

Extensive mitochondrial heteroplasmy in hybrid water frog (Pelophylax spp.) populations from Southeast Europe

Water frogs of the genus Pelophylax (previous Rana) species have been much studied in Europe for their outstanding reproductive mechanism in which sympatric hybridization between genetically distinct parental species produces diverse genetic forms of viable hybrid animals. The most common hybrid is P. esculentus that carries the genomes of both parental species, P. ridibundus and P. lessonae, but usually transfers the whole genome of only one parent to its offsprings (hybridogenesis). The evolutionary cost of transfer of the intact genome and hence the hemiclonal reproduction is the depletion of heterozygosity in the hybrid populations. Pelophylax esculentus presents an excellent example of the long‐term sustained hybridization and hemiclonal reproduction in which the effects of the low genetic diversity are balanced through the novel mutations and periodic recombinations. In this study, we analyzed the mitochondrial (mt) and microsatellites DNA variations in hybrid Pelophylax populations from southern parts of the Pannonian Basin and a north–south transect of the Balkan Peninsula, which are home for a variety of Pelophylax genetic lineages. The mtDNA haplotypes found in this study corresponded to P. ridibundus and P. epeiroticus of the Balkan – Anatolian lineage (ridibundus–bedriagae) and to P. lessonae and a divergent lessonae haplotype of the lessonae lineage. The mtDNA genomes showed considerable intraspecific variation and geographic differentiation. The Balkan wide distributed P. ridibundus was found in all studied populations and its nuclear genome, along with either the lessonae or the endemic epeiroticus genome, in all hybrids. An unexpected finding was that the hybrid populations were invariably heteroplasmic, that is, they contained the mtDNA of both parental species. We discussed the possibility that such extensive heteroplasmy is a result of hybridization and it comes from regular leakage of the paternal mtDNA from a sperm of one species that fertilizes eggs of another. In this case, the mechanisms that protect the egg from heterospecific fertilization and further from the presence of sperm mtDNA could become compromised due to their differences and divergence at both, mitochondrial and nuclear DNA. The heteroplasmy once retained in the fertilized egg could be transmitted by hybrid backcrossing to the progeny and maintained in a population over generations. The role of interspecies and heteroplasmic hybrid animals due to their genomic diversity and better fitness compare to the parental species might be of the special importance in adaptations to miscellaneous and isolated environments at the Balkan Peninsula.     

Hybrid Identification in Clivia(Amaryllidaceae) using Chromosome Banding and Genomic In Situ Hybridization

Giemsa C-banding and genomic in situ hybridization (GISH) wereused to identify parental genomes in hybrids of Clivia(Amaryllidaceae).Of the three groups reputed to be hybrids, onlyC. cyrtanthiflorawas shown to be of hybrid origin. The ‘German hybrids’and ‘Belgian hybrids’ were both shown to be karyotypicallyand genomically similar to C. miniata, and are either selectionsor intraspecific hybrids of that species. Successful genomedifferentiation in F₁hybrids by GISH required high stringencyand high ratios of blocking DNA to probe. The spatial dispositionof different genomes with C-band or GISH markers in the hybridswas investigated in two dimensions on the spread. In five artificiallyproduced hybrids, either C-banding or GISH was used to locatethe position of parental genomes in mitotic metaphase cells.In all cases there was a significant tendency for centromeresof the different parental genomes to occupy two distinct concentricdomains on the metaphase plate. The presence or absence of centromericheterochromatin was not correlated with genome disposition.Results show that chromosome analyses can be a useful way ofidentifying Clivia hybrids in their vegetative phase. Copyright2001 Annals of Botany Company Clivia, genomic in situ hybridization, cultivar origin, parental genome separation     

Rearrangements in the mitochondrial genome of somatic hybrid cell lines of Pennisetum americanum (L.) K. Schum. + Panicum maximum Jacq.

Summary Mitochondrial DNA from three somatic hybrid cell lines of Pennisetum americanum + Panicum maximum was compared with mitochondrial DNA of the parents. Gel electrophoresis of BamHI-restricted mitochondrial DNA indicated that extensive rearrangements had occurred in each of the three hybrid lines. The hybrid restriction patterns showed a combination of some bands from each parent plus novel fragments not present in either parent. Additional evidence for rearrangements was obtained by hybridization of eight DNA probes, carrying sequences of known coding regions, to Southern blots. Each of the somatic hybrids exhibited a partial combination of the parental mitochondrial genomes. These data suggest recombination or amplification of the mitochondrial genomes in the somatic hybrids.     

Dialect-I,species-specific repeated DNA sequence from barley,Hordeum vulgare

Summary Dialect-1, species-specific repetitive DNA sequence of barley Hordeum vulgare, was cloned and analysed by Southern blot and in situ hybridization. Dialect-1 is dispersed through all barley chromosomes with copy number 5,000 per genome. Two DNA fragments related to Dialect-1 were revealed in phage library, subcloned and mapped. All three clones are structurally heterogenous and it is suggested that the full-length genomic repeat encompassing Dialect-1 is large in size. The Dialect-1 DNA repeat is represented in the genomes of H. vulgare and ssp. agriocrithon and spontaneum in similar form and copy number; it is present in rearranged form with reduced copy number in the genomes of H. bulbosum and H. murinum, and it is absent from genomes of several wild barley species as well as from genomes of wheat, rye, oats and maize. Dialect-1 repeat may be used as a molecular marker in taxonomic studies and for identification of barley chromosomes in interspecies hybrids.     

Identification of the Genomic Constitution ofMusaL. Lines (Bananas, Plantains and Hybrids) Using Molecular Cytogenetics

The genomic constitutions of someMusaL. lines (bananas, plantainsand artificial hybrids) were identified using molecular cytogenetictechniques. Double targetin situDNA:DNA hybridization to chromosomespreads using as probes, total genomic DNA isolated from diploidMusalinesof known AA (labelled with biotin-11-dUTP) and BB (labelledwith digoxigenin-11-dUTP) genome constitution was carried out.The use of 60% acetic acid combined with heating over a flamegave high quality chromosome spreads free of cytoplasm forinsituhybridization. Total genomic A DNA labelled broad centromericregions of all 22 chromosomes of the diploid line, Calcutta4 (M. acuminataColla. ssp.burmanniccoides; A genome) with somechromosomes showing stronger hybridization. Labelled DNA fromthe B genome hybridized strongly to the centromeric regionsof all 22 chromosomes of Butohan 2 (M. balbisianaColla; B genome).The two satellited chromosomes of genome B labelled stronglywith genomic A DNA.In situhybridization of labelled A and Bgenomic DNA to metaphase chromosomes of triploid AAB and ABBcultivars discriminated between A and B genome chromosomes.The plantains Agbagba, Obino l'Ewai and Mbi Egome showed 22genome A and 11 genome B chromosomes while the cooking bananasBluggoe and Fougamou showed 11 genome A and 22 genome B chromosomes.Hybridization of labelled A and B genomic DNA to chromosomesof the hybrids showed that TMP2x 2829-62 has all 22 genome Achromosomes while TMPx 4698-1 has 33 genome A and 11 genomeB chromosomes.In situhybridization of labelled total genomicDNA to chromosomes has immense potential for identificationof chromosome origin and can be used to characterize cultivarsand hybrids produced inMusabreeding.Copyright 1997 Annals ofBotany Company Genomicin situhybridization; banana; plantain; hybrids; plant breeding; genome organization; biodiversity     

Identification,cloning and sequence analysis of a dwarf genome-specific RAPD marker in rubber tree [<Emphasis Type="Italic">Hevea brasiliensis</Emphasis> (Muell.) Arg.]

High-yielding dwarf clones of Hevea brasiliensis are tolerant to wind damage and therefore useful for high-density planting. The identification of molecular markers for the dwarf character is very important for isolating true-to-type high-yielding dwarf hybrid lines in the early stage of plant breeding programs. We have identified a dwarf genome-specific random amplified polymorphic DNA (RAPD) marker in rubber tree. A total of 115 random oligonucleotide 10-mer primers were used to amplify genomic DNA by PCR, of which 19 primers produced clear and detectable bands. The primer OPB-12 generated a 1.4-kb DNA marker from both natural and controlled F₁ hybrid progenies (dwarf stature) derived from a cross between a dwarf parent and a normal cultivated clone as well as from the dwarf parent; it was absent in other parent (RRII 118). To validate this DNA marker, we analyzed 22 F₁ hybrids (13 with a dwarf stature and nine with a normal stature); the dwarf genome-specific 1.4-kb RAPD marker was present in all dwarf-stature hybrids and absent in all normal-stature hybrids. This DNA marker was cloned and characterized. DNA marker locus specificity was further confirmed by Southern blot hybridization. Our results indicate that Southern blot hybridization of RAPD using probes made from cloned DNA fragments allows a more accurate analysis of the RAPD pattern based on the presence/absence of specific DNA markers than dye-stained gels or Southern blot analysis of RAPD blots using probes made from purified PCR products. Detection of RAPD markers in the hybrid progenies indicates that RAPD is a powerful tool for identifying inherited genome segments following different hybridization methods in perennial tree crops.     

Differential fate of plastid and mitochondrial genomes in Petunia somatic hybrids

Summary The chloroplast (cp) and mitochondrial (mt) DNAs of Petunia somatic hybrid plants, which were derived from the fusion of wild-type P. parodii protoplasts with albino P. inflata protoplasts, were analyzed by endonuclease restriction and Southern blot hybridization. Using ³²P-labelled probes that distinguished the two parental cpDNAs at a BamH1 site and at a HpaII site, only the P. parodii chloroplast genome was detected in the 10 somatic hybrid plants analyzed. To examine whether cytoplasmic mixing had resulted in rearrangement of the mitochondrial genome in the somatic hybrids, restriction patterns of purified somatic hybrid and parental mtDNAs were analyzed. Approximately 87% of those restriction fragments which distinguish the two parental genomes are P. inflata-specific. Restriction patterns of the somatic hybrid mtDNAs differ both from the parental patterns and from each other, suggesting that an interaction occurred between the parental mitochondrial genomes in the somatic fusion products which resulted in generation of the novel mtDNA patterns. Southern blot hybridization substantiates this conclusion. In addition, somatic hybrid lines derived from the same fusion product were observed to differ in mtDNA restriction pattern, reflecting a differential sorting-out of mitochondrial genomes at the time the plants were regenerated.     

Nuclear and cytoplasmic genome composition of Solanum bulbocastanum (+) S. tuberosum somatic hybrids.

Somatic hybrids between the wild incongruent species Solanum bulbocastanum (2n = 2x = 24) and S. tuberosum haploids (2n = 2x = 24) have been characterized for their nuclear and cytoplasmic genome composition. Cytologic observations revealed the recovery of 8 (near-)tetraploid and 3 hexaploid somatic hybrids. Multicolor genomic in situ hybridization (GISH) analysis was carried out to study the genomic dosage of the parental species in 5 somatic hybrids with different ploidy. The GISH procedure used was effective in discriminating parental genomes in the hybrids; most chromosomes were unambiguously colored. Two (near-)tetraploid somatic hybrids showed the expected 2:2 cultivated-to-wild genomic dosage; 2 hexaploids revealed a 4:2 cultivated-to-wild genomic dosage, and 1 hexaploid had a 2:4 cultivated-to-wild genomic dosage. Characterization of hybrid cytoplasmic genomes was performed using gene-specific primers that detected polymorphisms between the fusion parents in the intergenic regions. The analysis showed that most of the somatic hybrids inherited the plastidial and mitochondrial DNA of the cultivated parent. A few hybrids, with a rearranged mitochondrial genome (showing fragments derived from both parents), were also identified. These results confirmed the potential of somatic hybridization in producing new variability for genetic studies and breeding.     

Reciprocal allopolyploid grasses (Festuca × Lolium) display stable patterns of genome dominance

Allopolyploidization entailing the merger of two distinct genomes in a single hybrid organism, is an important process in plant evolution and a valuable tool in breeding programs. Newly established hybrids often experience massive genomic perturbations, including karyotype reshuffling and gene expression modifications. These phenomena may be asymmetric with respect to the two progenitors, with one of the parental genomes being “dominant.” Such “genome dominance” can manifest in several ways, including biased homoeolog gene expression and expression level dominance. Here we employed a k-mer–based approach to study gene expression in reciprocal Festuca pratensis Huds. × Lolium multiflorum Lam. allopolyploid grasses. Our study revealed significantly more genes where expression mimicked that of the Lolium parent compared with the Festuca parent. This genome dominance was heritable to successive generation and its direction was only slightly modified by environmental conditions and plant age. Our results suggest that Lolium genome dominance was at least partially caused by its more efficient trans-acting gene expression regulatory factors. Unraveling the mechanisms responsible for propagation of parent-specific traits in hybrid crops contributes to our understanding of allopolyploid genome evolution and opens a way to targeted breeding strategies.     

Production of a highly asymmetric somatic hybrid between rice and Zizania latifolia (Griseb): evidence for inter-genomic exchange

 A highly asymmetric and fertile somatic hybrid plant was obtained via protoplast fusion in an intergenric combination. Gamma-ray-irradiated Zizania latifolia (Griseb). Turcz. ex Stapf mesophyll protoplasts were electrofused with idoacetamide-inactivated rice protoplasts derived from a 2-month-old suspension cell culture. Two of the six putative hybrid calli regenerated plants. Cytological observation showed that the somatic chromosome numbers of both plants were the same as the rice parent (2n=24). Nevertheless, the hybrid nature and inter-genomic exchange events of one of the plants, i.e. SH6 (SH for somatic hybrid), were confirmed by Southern analysis using both total genomic DNA and moderate-copy, Z. latifolia-abundant DNA sequences as probes; in both cases, parental specific and/or new intergenomic recombinant hybridization fragments were detected. In both plant and seed morphology, the hybrid (SH6) was distinct from its rice parental cultivar, as well as from the wild donor species, Z. latifolia. Received: 15 August 1998 / Accepted: 30 September 1998     

Independent segregation of the plastid genome and cytoplasmic male sterility in Petunia somatic hybrids

Summary The chloroplast genomes of three sets of Petunia somatic hybrids were analyzed to examine the relationship between chloroplast DNA (cpDNA) composition and cytoplasmic male sterility (CMS). Chloroplast genomes of somatic hybrid plants were identified either by restriction and electrophoresis of purified cpDNAs or by hybridization of total DNA digests with cloned cpDNA probes that distinguish the parental genomes.The chloroplast genomes of a set of seven somatic hybrids derived from the fusion of Petunia CMS line 2423 and fertile line 3699 were analyzed. All seven plants were fertile, and all exhibited the cpDNA restriction pattern of the sterile cytoplasm. Similarly, four fertile somatic hybrids derived from the fusion of CMS line 3688 and fertile line 3677 were found to contain the CMS chloroplast genome. The cpDNA compositions of four fertile and two sterile somatic hybrids derived from the fusion of CMS line 3688 and fertile line 3704 were determined by restriction analysis of purified cpDNAs; all six plants exhibited the cpDNA restriction pattern of line 3704. Thus the CMS phenotype segregates independently of the chloroplast genome in Petunia somatic hybrids, indicating that CMS in Petunia is not specified by the chloroplast genome.     

Isolation and chromosomal distribution of a novel Ty1-copia-like sequence fromSecale, which enables identification of wheat—Secale africanum introgression lines

A repetitive sequence of 411 bp, named pSaO5₄₁₁, was identified in theSecale africanum genome (R^a) by random amplified polymorphic DNA (RAPD) analysis of wheat and wheat—S. africanum amphiploids. GenBank BLAST search revealed that the sequence of pSaO5₄₁₁ was highly homologous to a part of a Ty1-copia retrotransposon. Fluorescence in situ hybridization (FISH) analyses indicated that pSaO5₄₁₁ was significantly hybridized toS. africanum chromosomes of a wheat—S. africanum amphiploid, and it was dispersed along theSecale chromosome arms except the terminal regions. Basing on the sequence of pSaO5₄₁₁, a pair of sequence-characterized amplified region (SCAR) primers were designed, and the resultant SCAR marker was able to target both cultivated rye and the wildSecale species, which also enabled to identify effectively theS. africanum chromatin introduced into the wheat genome.     

Isolation and characterization of genome-specific DNA sequences in Triticeae species

Two contrasting genome-specific DNA sequences were isolated from Aegilops speltoides (wild goat grass) and Hordeum chilense (wild barley), each representing more than 1 % of the genomes. These repetitive DNA fragments were identified as being genome-specific before cloning by genomic Southern hybridization (using total genomic DNA as a probe), and hence extensive screening of clones was not required. For each fragment, up to six recombinant plasmid clones were screened and about half were genome-specific. Clone pAesKB52 from Ae. speltoides was a 763 by EcoRI fragment, physically organized in simple tandem repeats and shown to localize to sub-telomerec chromosome regions of species with the Triticeae S-genome by in situ hybridization to chromosomes. The sequence data showed an internal duplication of some 280 bp, which presumably occurred before sequence amplification and dispersion, perhaps by unequal crossing-over or reciprocal translocation. In situ hybridization showed that the sequence distribution varied between closely related (S-genome) species. Clone pHcKB6 was a 339 by DraI fragment from H. chilense, also tandemly repeated but more variable; loss of the DraI site resulting in a ladder pattern in Southern blots which had little background smear. In situ hybridization showed that the tandem repeats were present as small clusters dispersed along all chromosome arms except at a few discrete regions including the centromeres and telomeres. The clone hybridized essentially specifically to the H-genome of H. chilense and hence was able to identify the origin of chromosomes in a H. chilense x Secale africanum hybrid by in situ hybridization. It has a high A + T content (66%), small internal duplications, and a 50 by degenerate inverted repeat. We speculate that it has dispersed by retrotransposition in association with other sequences carrying coding domains. The organization and evolution of such sequences are important in understanding long-range genome organization and the types of change that can occur on evolutionary and plant breeding timescales. Genome-specific sequences are also useful as markers for alien chromatin in plant breeding.     

Genomic alterations in the interspecific hybrid Helianthus annuus×Helianthus tuberosus

 The genome of a Helianthus annuus (2n=34) ×Helianthus tuberosus (2n=102) hybrid was studied at cytological, biochemical and molecular levels and compared to those of the parental species. Cytophotometric analyses showed that the hybrid has a 4C DNA content higher than expected and with a larger variability than in the parents. This high variability is probably not related to chromosome-number variations since the hybrid always had 2n=68 chromosomes. Moreover, hybrid interphase nuclei showed lower heterochromatin condensation than the parental ones. Thermal denaturation of genomic DNAs indicated that quantitative variation of some DNA families occurred in the hybrids compared to parents. Finally, molecular analyses of DNAs restricted with different enzymes, after Southern blotting and hybridization with HR probes, showed restriction patterns in the hybrid different from those observed in parents. These results indicate that interspecific hybridization between H. annuus and H. tuberosus may determine quantitative variation of some DNA families and differential DNA methylations that probably modify the nuclear structure. These phenomena are probable responses to a “genomic shock” following the interspecific cross. Received: 22 May 1998 / Accepted: 4 June 1998     

Genomic in situ hybridization to identify alien chromosomes and chromosome segments in wheat

Summary Genomic in situ hybridization was used to identify alien chromatin in chromosome spreads of wheat, Triticum aestivum L., lines incorporating chromosomes from Leymus multicaulis (Kar. and Kir.) Tzvelev and Thinopyrum bessarabicum (Savul. and Rayss) Löve, and chromosome arms from Hordeum chilense Roem. and Schult, H. vulgare L. and Secale cereale L. Total genomic DNA from the introgressed alien species was used as a probe, together with excess amounts of unlabelled blocking DNA from wheat, for DNA:DNA in-situ hybridization. The method labelled the alien chromatin yellow-green, while the wheat chromosomes showed only the orange-red fluorescence of the DNA counterstain. Nuclei were screened from seedling root-tips (including those from half-grains) and anther wall tissue. The genomic probing method identified alien chromosomes and chromosome arms and allowed counting in nuclei at all stages of the cell cycle, so complete metaphases were not needed. At prophase or interphase, two labelled domains were visible in most nuclei from disomic lines, while only one labelled domain was visible in monosomic lines. At metaphase, direct visualization of the morphology of the alien chromosome or chromosome segment was possible and allowed identification of the relationship of the alien chromatin to the wheat chromosomes. The genomic in-situ hybridization method is fast, sensitive, accurate and informative. Hence it is likely to be of great value for both cytogenetic analysis and in plant breeding programmes.     

Parental genome composition and genetic classifications of derivatives from intergeneric crosses of Festuca mairei and Lolium perenne

Intergeneric hybridization between Festuca and Lolium has been a long-term goal of forage and turfgrass breeders to generate improved cultivars by combining stress tolerance of Festuca and rapid establishment of Lolium. However, wide-distance hybridizations usually result in the wild genome being eliminated from the hybrid due to incomplete chromosome pairing and crossovers. In this study, random amplified polymorphic DNA (RAPD) and simple sequence repeat (SSR) markers were used to detect the parental genome composition of F₁ hybrids and backcross, generated from crosses between Festuca mairei St. Yves (Fm) and Lolium perenne L. (Lp). Each of the hybrids exhibited integration of Fm and Lp genomes with varying levels of Fm/Lp genome ratios. However, cluster and principle component analyses of the progeny consistently revealed four groups depending on the amount of genome introgression from both parents. The parental genome composition and classifications of intergeneric progeny would be useful for breeding material selection. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The allopolyploid origin of Narcissus obsoletus (Alliaceae): identification of parental genomes by karyotype characterization and genomic in situ hybridization

Karyological and genomic in situ hybridization (GISH) approaches provided evidence of the parentage and origin of the hybrid species Narcissus obsoletus. Here, we demonstrate that the putative parental species, N. serotinus L. and N. elegans (Haw.) Spach, recently proposed because of their intermediate morphological traits, have participated in the hybridization process forming this taxon. Karyotype characterization of parental genomes in populations from S Spain and N Morocco has revealed differences in chromosome length and karyotype asymmetry, highlighting their diploid nature. Multicolour GISH on metaphase plates of N. obsoletus, with N. serotinus and N. elegans DNA used as probes, showed differential fluorescent staining of 10 and 20 chromosomes from parental genomes, respectively. Both parental genomes were detected in the allopolyploid, albeit in a duplicated manner. Secondary hybridization between N. obsoletus and N. serotinus was also detected karyologically. Little karyological differentiation between different geographic regions was found in either N. serotinus or N. obsoletus. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159 , 477–498.