Alloploid Nature Research Articles

Distribution, Polymorphism and Function Characteristics of the GST-Encoding Fhb7 in Triticeae.

Encoding a glutathione S-transferase (GST) and conferring resistance to Fusarium head blight (FHB), Fhb7 was successfully isolated from the newly assembled Thinopyrum elongatum genome by researchers, with blasting searches revealing that Thinopyrum gained Fhb7 through horizontal gene transfer from an endophytic Epichloë species. On the contrary, our molecular evidence reveals that the homologs of Fhb7 are distributed commonly in Triticeae. Other than Thinopyrum, the Fhb7 homologs were also detected in four other genera, Elymus, Leymus, Roegneria and Pseudoroegneria, respectively. Sequence comparisons revealed that the protein sequences were at least 94% identical across all of the Fhb7 homologs in Triticeae plants, which in turn suggested that the horizontal gene transfer of the Fhb7 might have occurred before Triticeae differentiation instead of Thinopyrum. The multiple Fhb7 homologs detected in some Triticeae accessions and wheat-Thinopyrum derivatives might be attributed to the alloploid nature and gene duplication during evolution. In addition, we discovered that some wheat-Thinopyrum derivatives carrying the Fhb7 homologs had a completely different reaction to Fusarium head blight, which made us question the ability of the GST-encoding Fhb7 to resist FHB.

Sympatric and allopatric niche shift of endemic Gypsophila (Caryophyllaceae) taxa in the Iberian Peninsula.

Several species of the Gypsophila genus are endemic to the Iberian Peninsula, including gypsophytes of particular ecological, evolutionary and biochemical interest, and taxa that have undergone both sympatric and allopatric genetic differentiation. The niche shift among these taxa has been assessed using ecological niche modelling and ordination techniques, adopting a niche overlap approach to compare the similarity and equivalency of the ecological niches. We used the Maximum Entropy method to study the potential distribution of these taxa in different eras: the Last Glacial Maximum (LGM), the Mid Holocene and the current conditions. We present evidence of niche shift during the speciation of G. bermejoi, with a strong niche overlap between the parental taxa (G. struthium subsp. struthium and G. tomentosa), yet both overlap much more weakly with the hybrid species. This phenomenon may be explained by genetic and epigenetic interactions, and it has been described in other species. We also studied the sister subspecies G. struthium subsp. struthium and G. struthium subsp. hispanica, with mostly allopatric distributions and with the Iberian System mountain range acting as a geographical barrier. The Iberian System and other mountain ranges may have favored differences in the climatic conditions on either side of the mountain range, which is consistent with an incipient process of bioclimatic ecological speciation. These results seem to indicate that niche shift can occur over very different timespans. In the case of G. bermejoi, speciation may have produced significant niche shifting in one or two generations due to its alloploid nature. By contrast, G. struthium subsp. struthium and G. struthium subsp. hispanica seem to have undergone a more gradual process of allopatric genetic differentiation driven by bioclimatic factors. Both these processes are relatively recent and they will have been strongly influenced by the climate change at the end of LGM.

Isoenzyme variation in barley (Hordeum L.) 2. Aspartate aminotransferase and 6-phosphoglyconate dehydrogenase

Isoenzymes of aspartate aminotransferase (AAT) and 6-phosphoglyconate dehydrogenase (PGD) have been studied by polyacrylamide gel electrophoresis (PAGE) to elucidate phylogenetic relationships among Eurasian barley species. H. vulgare, H. spontaneum and H. bulbosum share the same electrophoretic phenotype of AAT different from those of the Murina group. This supports the inclusion of H. bulbosum in the type section, but argues against the inclusion of the Murina group. H. murinum s. str. (4x) and H. hrasdanicum (6x) of the Murina group have different heterozygous phenotypes of PGD, suggesting their alloploid nature. H. hrasdanicum reveals fixation of additional heterozygosity at two AAT loci. No accession of H. glaucum (2x) was found, fitting the donor of any of the genomes of H. murinum and H. hrasdanicum. The annuals of the series Marina differ distinctly from the Murina annuals of the section Trichostachys in some isoenzymes. They are removed from the section Trichostachys in a new section Marina (NEVSKI) JAASKA stat.nov. H. marinum ssp. gussoneanum tetraploids (= H. geniculalum auct.) show fixation of heterozygosity at two AAT loci, suggesting their alloploid nature. The outcrossing perennials H. bulbosum and H. brevisubulatum s. 1. show allozymic polymorphism of AAT-B and AAT-C, but are invariant in PGD-A. H. secalinum and H. jubatum share fixed heterozygosity of AAT-B, favouring their alloploid nature.

Isoenzyme variation in barley (Hordeum L.)

Isoenzymes of aspartate aminotransferase (AAT) and 6-phosphoglyconate dehydrogenase (PGD) have been studied by polyacrylamide gel electrophoresis (PAGE) to elucidate phylogenetic relationships among Eurasian barley species. H. vulgare, H. spontaneum and H. bulbosum share the same electrophoretic phenotype of AAT different from those of the Murina group. This supports the inclusion of H. bulbosum in the type section, but argues against the inclusion of the Murina group. H. murinum s. str. (4x) and H. hrasdanicum (6x) of the Murina group have different heterozygous phenotypes of PGD, suggesting their alloploid nature. H. hrasdanicum reveals fixation of additional heterozygosity at two AAT loci. No accession of H. glaucum (2x) was found, fitting the donor of any of the genomes of H. murinum and H. hrasdanicum. The annuals of the series Marina differ distinctly from the Murina annuals of the section Trichostachys in some isoenzymes. They are removed from the section Trichostachys in a new section Marina (Nevski) Jaaska stat.nov. H. marinum ssp. gussoneanum tetraploids (=H. geniculalum auct.) show fixation of heterozygosity at two AAT loci, suggesting their alloploid nature. The outcrossing perennials H. bulbosum and H. brevisubulatum s. 1. show allozymic polymorphism of AAT-B and AAT-C, but are invariant in PGD-A. H. secalinum and H. jubatum share fixed heterozygosity of AAT-B, favouring their alloploid nature.

Intergeneric hybridization between Hordeum and Secale II. Analysis of meiosis in hybrids

Forty-one (41) intergeneric cross combinations between Hordeum and Secale were analysed for meiotic MI chromosome pairing. Hordeum taxa used in these hybrids included diploid, tetraploid, and hexaploid cytotypes. Differences between the sizes of the chromosomes of Hordeum and Secale allowed distinction between auto- and allosyndetic pairing. Allosyndesis was very rare, indicating lack of homology between any of the genomes of Hordeum (H, I, “X”, “Y”) and the R-genome of Secale. Autosyndetic pairing among Hordeum chromosomes occurred in the hybrids involving polyploid species of Hordeurn. The segmental alloploid nature of H. brachyantherum, H. jubatum, H. lechleri, H. arizonicum, H. procerum, H. capense. and H. secalinum was confirmed, but it is suggested that the annual H. depressum is an autotetrdploid. In general the level of autosyndetic pairing among the Hordeum chromosomes was higher in the intergeneric combinations with Secale than in corresponding Hordeum polyhaploids. It is suggested that the genome of Secale exerts influence during synaptonemal complex formation, allowing a higher level of crossing-over between the chromosomes of Hordeum.

Isoenzyme Data on the Genetic Divergence and Allopolyploidy in the Section Genea of the Grass Genus Bromus (Poaceae)

~Electrophoretic variation of isoenzyme characters of ten enzymes (ADH, AAD, MDH, SKD, AAT, SOD, PRX, PGD, PGI, LAP) has been studied in five brome species, comprising the section Genea of the genus Bromus. The three polyploids, B. madritensis, B. rubens and B. diandrus (incl. B. rigidus), exhibited different fixed heterozygosities of several heterozymes, suggesting their alloploid nature. The morphologically similar polyploids B. madritensis and B. rubens differed in seven heterozymes out of fourteen studied, supporting their specific recognition. The two diploids, B. sterilis and B. rectorurn, differed in four heterozymes. One genome of the polyploid species corresponded closely to that of B. sterilis. All species of the section could be distinguished from each other by diagnositic isoenzyme phenotypes. Bromus diandrus and B. rigidus revealed identical zymograms, providing new support for their conspecific recognition.

Isoenzyme diversity and phylogenetic affinities in the section Bromus of the grass genus Bromus (Poaceae)

Abstract Allozyme variation of eleven heterozymes of nine enzymes was analyzed for fourteen annual brome species in the type section of the genus Bromus with the use of PAGE. Diploids B . japonicus and B. squarrosus had identical zymograms, providing new evidence about their very close genetic relationships. Tetraploids B. secalinus and B . commutatus had very similar enzyme phenotypes, indicating their strong genetic affinity, but still differed in PRX-F homoeozymes of one composite genome. Diploid B. alopecuros appears to be the donor of one genome in the tetraploid B. lanceolatus . Bromus pseudosecalinus could not be one of the diploid progenitors for B . secalinus . 6-PGD gene is duplicated and diverged in several diploids of the section Bromus. All tetraploids studied exhibited different fixed heterozygosities of several heterozymes, suggesting their alloploid nature.

Molecular characterization and chromosome location of repeated DNA sequences in Hordeum species and in the amphiploid tritordeum (x Tritordeum Ascherson et Graebner).

Genomic DNA from 19 species and subspecies representing the four basic genomes (H, I, X, and Y) of Hordeum was restricted with HaeIII and hybridized with two repeated DNA sequences of Hordeum chilense. The potential use of repeated sequences in ascertaining genomic affinities within the genus Hordeum was studied by comparing restriction fragment patterns. The study demonstrated the following: (i) species that shared a basic genome showed more similar hybridization fragment patterns than species with different genomes, whether with pHch1 or pHch3; (ii) hybridization with pHch1 revealed the presence of certain fragments limited to the species with a H genome; and (iii) the alloploid nature of species like H. jubatum was confirmed. The chromosomal distribution of the two repeated sequences was studied in species representing each basic genome and in the amphiploid tritordeum using fluorescent in situ hybridization. No interspecific differences were found between the diploid species. In situ experiments indicated the alloploid nature of H. depressum. Both sequences allow H. chilense chromatin to be distinguished from wheat chromosomes in tritordeum.

Cytological Studies in the South Indian Acanthaceae. 1. Genus Barleria L.

Cytology of eight species of Barleria from South India is reported. All the species have n=20 and 2n=40. Meiosis was fairly normal in all except one species (B. courtallica) in which IV, III, II and Is were consistently noticed. Somatic chromosomes were large sized, and the karyotypes were fairly symmetrical and unspecialised (2B) in all except B. acwninata (3B).All the known species are tetraploids based on x=10. Meiotic behaviour in all the present species except B. courtallica was suggestive of their alloploid nature, while B. courtallica auto-tetraploid.Cytological evidence is shown to support separation of Barleria (large sized chromosomes) from Bentham and Hooker's Justicieae as done by Lindau and Bremekamp. Further, the delinking of Barleria (x=10, large chromosomes and trinucleate pollen) and Lepidagathis, (x=11, small chromosomes, and binucleate pollen) from Lindau's same tribal fold and their placement in different tribes proposed by Bremekamp is pointed out to be appropriate.

The Diploidised Meiosis of Tetraploid Beta macrocarpa and its Possible Application in Breeding Sugar Beet

AbstractAccessions of Beta macrocarpa Guss., collected on the Canary Islands, were tetraploid (2n = 36). Three of these accessions were studied in detail. The plants were rather uniform in their morphological appearance, both within and between accessions, and were annual and fully self‐compatible. Meiosis was completely diploidised, suggesting an alloploid nature of the tetraploid species. Crosses with diploid B. vulgaris yielded triploid hybrids which were sterile or nearly so; a few descendants of such hybrids were highly aneuploid. Crosses between tetraploid B. macrocarpa and autotetraploid cytotypes of B. vulgaris showed variable results, only part of these crosses yielded tetraploid hybrids. The tetraploid hybrids exhibited somewhat higher fertility than the triploids. An F2 generation showed partial hybrid dwarfness, partial fertility and segregation for carliness and coloration of the hypocotyl. All hybrids had multivalents at meiosis (averages: 2.5—5.4 multivalents per pollen mother cell), indicating suppression of the diploidised meiosis. The possibilities of application of the diploidised meiosis in breeding sugar beet are discussed.

Assessment of chromosome associations in haploids and their parental accessions in Hordeum

Meiotic pairing was studied in the following species and their haploid derivatives: Hordeum cordobense 2x, H. marinum 2x and 4x, H. secalinum 4x, H. capense 4x, H. jubatum 4x, H. brachyantherum 4x and 6x, H. lechleri 6x, and H. procerum 6x. The study revealed (i) homologous pairing in diploid species and very little nonhomologous associations in their mono-haploids; (ii) the alloploid nature of the polyploid taxa; (iii) a certain degree of homoeologous pairing in polyhaploids despite the diploid-like meiotic behaviour of the polyploids; (iv) genetic variation in the suppression of homoeologous chromosome pairing in different Hordeum species.Key words: Hordeum, meiotic pairing, haploids.

Genome Analysis of the Tetraploid Pseudoroegneri tauri1

The alloploid nature of some tetraploid accessions of Pseudoroegneria tauri (Boiss. & Bal.) A. Löve and P. spicata (Pursh) A. Löve was investigated by conducting meiotic analyses of the following hybrids: P. tauri (2n=28) ✕ P. libanotica (Hackel) D.R. Dewey (2n=14, genomes SS); P. tauri ✕ P. spicata (2n=14, genomes SS); P. tauri ✕ P. spicata (allo‐4x, 2n=28, genomes SSXX); P. tauri ✕ Agropyron cristatum (L.) Gaertn. (2n=14, genomes PP); and P. tauri ✕ A. cristatum (2n=28, genomes PPPP). Meiotic data of these hybrids showed that P. tauri possessed both the S and P genomes, and it had only the S genome in common with the allotetraploid P. spicata. Mitotic cells showed 14 short and 14 long chromosomes in P. tauri; 14 short and 7 long chromosomes in P. tauri ✕ P. libanotica; and 14 long and 7 short chromosomes in P. tauri ✕ A. cristatum. It is concluded that two tetraploid accessions of P. tauri from Iran used in this study have the PPSS genome formula in which the long chromosomes are those of the P genome and the short ones are those of the S genome. An unknown (X) genome present in allotetraploid P. spicata differs from both the S and the P genomes, and possibly is an H genome. This study revealed that the alloploid nature of P. tauri, and possibly some tetraploid P. spicata accessions, is not due to the presence of a Ph‐like genetic system because of the high frequencies of nonhomologous pairing or incomplete preferentiality observed in these triploid and tetraploid hybrids. In view of these findings, forage grass breeders should not use these amphiploids in crosses with autotetraploid species in the genus Pseudoroegneria. Taxonomists must find a way to classify the natural amphiploid species with PPSS genomes.

Cytology of woody species

Cytological studies have been made on 59 woody species of Polypetalae. Two genera (Gynocardia odorata,n=23;Pahudia martabanica,n=12) and 9 species (Talauma candollei,n=19;Cratoxylon polyanthum,n=11;Sterculia villosa,n=20;Grewia hirsuta,n=9;Millettia brandisiana, 2n=22+0−2B;Phanera glauca,n=14;Terminalia oliveri,n=12;Psidium coriaceum, 2n=77;P. pumilum,n=11) are counted for the first time. Additional and/or varied chromosome numbers are recorded for 8 species. Presence ofB-Chromosomes has been detected inCrataeva nurvala (n=13+0−3B),Erythrina caffra (n=21+0−3B) andMillettia brandisiana (2n=22+0−2B). Existence of some multivalents in the tetraploid taxa ofEugenia jambolana (2n=44) andHydnocarpus laurifolia (2n=48) indicates their segmental alloploid nature. But the presence of cent per cent trivalents (11III) in the triploid cytotype ofEugenia uniflora (2n=33) reveals the autotriploid nature. Presence of some univalents in diploid taxa ofMillettia brandisiana (2n=22) may be due to asynapsis and/or desynapsis. Variation in chromosome number inPMCs and some pollen sterility inHydnocarpus kurzii seems to be the consequence of cytomixis. Abnormalities in microsporogenesis in one of the cultivated trees ofFirmiana pallens (2n=40) are due to spindle irregularities.

Allozymes and genetic variability in Medicago turbinata, M. truncatula, and their hybrids

The genetic variability in the diploid annual species (2n = 2x = 16) Medicago turbinata L. and M. truncatula Gaernt. was studied at three loci for the enzymes peroxidase, Prx1-1, and leucine-aminopeptidase, Lap1-1 and Lap1-2. Eight accessions of each species, including all the taxonomic forms were surveyed by starch gel electrophoresis. No variation was observed among plants within each accession. Among the M. turbinata forms, four alleles were observed at locus Lap1-2. No variation was detected for the other two loci studied. For the M. truncatula forms, four alleles were found for Prx1-1 and three alleles for Lap1-2. No variation was observed for locus Lap1-1. Form uncinata of M. truncatula, of uncertain taxonomic status, has at least one M. turbinata allele. Both species can be differentiated by their specific allozymes. In general, the alleles of the isozymic loci segregated in a Mendelian fashion in the expected ratios for monomeric enzymes. The presence of chlorophyll-deficient plants on some of the progenies involving different taxonomic forms of the species M. turbinata indicates the presence of isolation barriers between these forms. The lack of segregation at locus Lap1-1 in the tetraploidized interspecific hybrid proves its alloploid nature.

Meiosis in polyhaploid Hordeum: hemizygous ineffective control of diploid-like behaviour in a hexaploid?

Meiotic chromosome behaviour was studied in the hexaploid Hordeum parodii (2n=6x=42) and in six haploids (2n=3x=21) obtained from a cross between H. parodii and H. bulbosum (2n=2x=14) whereby all bulbosum chromosomes were selectively eliminated. The alloploid nature of H. parodii was evident from the exclusive bivalent formation at the hexaploid level and the low and variable number of bivalents in its haploid derivatives. In haploids, both nonhomologous (intragenomic) and homoeologous (intergenomic) chromosomes paired at prophase. Foldbacks in single chromosomes, bivalents and trivalents were observed at prophase and metaphase I. At diakinesis, the associations involved a maximum of 20 chromosomes which decreased to 12 by metaphase I. This decrease was attributed to the failure of the non-homologous associations to persist until metaphase I. A “hemizygous-ineffective” control for the diploid-like behaviour of the hexaploid parodii is proposed to explain the homeologous chromosome pairing in its haploid derivatives.