The heterochromatin distribution and genome evolution in diploid species of Elymus and Agropyron
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The acetocarmine–Giemsa C-banding technique was used to study heterochromatin distribution in somatic chromosomes of diploid Elymus junceus (= Psathyrostachys juncea) (2n = 14) (genome designation Ju = N) and nine diploid Agropyron species (2n = 14): A. cristatum (C = P), A. imbricatum (C = P), A. elongatum (= Elytrigia elongata = Thinopyrum elongatum) (E = J), A. junceum (= E. bessarabicum = T. bessarabicum) (J = E), A. spicatum (= Pseudoroegneria spicata) (S), A. libanoticum (= P. libanotica) (S), A. ferganense (S), A. stipifolium (= P. stipifolia) (S), and A. velutinum (V). With the exception of A. elongatum and A. velutinum, which were self-fertile, all species were cross-pollinating and self-sterile. The cross-pollinating species showed large terminal C-bands and a high level of C-band polymorphism. Agropyron elongatum, moderately self-fertile, showed small terminal and interstitial bands and a minimal C-band polymorphism. Agropyron velutinum, fully self-fertile, almost totally lacked C-bands. The Ju, C, E, and J genomes appeared to be distinctive and the equivalence of the E and J genomes was not supported from their C-banding patterns. Four species sharing the S genome, A. spicatum, A. libanoticum, A. ferganense, and A. stipifolium had C-band patterns similar to one another, although C-bands were less prominent in A. stipifolium than others.Key words: C-banding, karyotype, wheatgrass, cytology.Keywords:
Elymus
Agropyron
Agropyron cristatum
Constitutive heterochromatin
Polyploid
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The acetocarmine–Giemsa C-banding technique was used to study heterochromatin distribution in somatic chromosomes of diploid Elymus junceus (= Psathyrostachys juncea) (2n = 14) (genome designation Ju = N) and nine diploid Agropyron species (2n = 14): A. cristatum (C = P), A. imbricatum (C = P), A. elongatum (= Elytrigia elongata = Thinopyrum elongatum) (E = J), A. junceum (= E. bessarabicum = T. bessarabicum) (J = E), A. spicatum (= Pseudoroegneria spicata) (S), A. libanoticum (= P. libanotica) (S), A. ferganense (S), A. stipifolium (= P. stipifolia) (S), and A. velutinum (V). With the exception of A. elongatum and A. velutinum, which were self-fertile, all species were cross-pollinating and self-sterile. The cross-pollinating species showed large terminal C-bands and a high level of C-band polymorphism. Agropyron elongatum, moderately self-fertile, showed small terminal and interstitial bands and a minimal C-band polymorphism. Agropyron velutinum, fully self-fertile, almost totally lacked C-bands. The Ju, C, E, and J genomes appeared to be distinctive and the equivalence of the E and J genomes was not supported from their C-banding patterns. Four species sharing the S genome, A. spicatum, A. libanoticum, A. ferganense, and A. stipifolium had C-band patterns similar to one another, although C-bands were less prominent in A. stipifolium than others.Key words: C-banding, karyotype, wheatgrass, cytology.
Elymus
Agropyron
Agropyron cristatum
Constitutive heterochromatin
Polyploid
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There is a high level of genetic isolation between Agropyron Gaertn. species and other Triticeae genera and hybrids. However, genetic distances between Hordeum spp. and Agropyron spp. are lacking. By crossing a tetraploid‐induced Hordeum chilense Roem. et Schult. and a tetraploid Agropyron cristatum (L.) Gaertn, euploid (2n=4x=28) and aneuploid (2n=4x=29) hybrids plants were obtained by embryo rescue. One of the euploid hybrids exhibited complete autosyndetic chromosome pairing during meiosis by forming 14 bivalents. In addition, this euploid was partially fertile. In situ hybridization with genomic DNA proved that the hybrid plants were true amphiploids. At metaphase I of meiosis in the amphiploid, two sets of paired and differentially stained chromosomes were observed. The meiotic pairing was higher between H. chilense (0.45 univalents) than between A. cristatum chromosomes (1.98 univalents). The amphiploid morphology is intermediate between those of the parents, although the spike morphology is generally closer to Agropyron.
Agropyron cristatum
Agropyron
Triticeae
Elymus
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Evolutionary chromosome change involves significant variation in DNA amount in diploids and genome downsizing in polyploids. Genome size and karyotype parameters of Hippeastrum species with different ploidy level were analysed. In Hippeastrum, polyploid species show less DNA content per basic genome than diploid species. The rate of variation is lower at higher ploidy levels. All the species have a basic number x = 11 and bimodal karyotypes. The basic karyotypes consist of four short metacentric chromosomes and seven large chromosomes (submetacentric and subtelocentric). The bimodal karyotype is preserved maintaining the relative proportions of members of the haploid chromosome set, even in the presence of genome downsizing. The constancy of the karyotype is maintained because changes in DNA amount are proportional to the length of the whole-chromosome complement and vary independently in the long and short sets of chromosomes. This karyotype constancy in taxa of Hippeastrum with different genome size and ploidy level indicates that the distribution of extra DNA within the complement is not at random and suggests the presence of mechanisms selecting for constancy, or against changes, in karyotype morphology.
Polyploid
Genome size
Nuclear DNA
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Citations (43)
Spermatocyte
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Karyotypes of eight tetraploid (2n = 28) South American species of Elymus, were symmetrical (arm ratios: 0 70-0.78) and uniform (intrachromosomal asymmetry index: 0.105-0 133). Significant differences in arm ratio and asymmetry index were found among tetraploid species and also among geographically isolated populations within one species. Variation was nearly continuous, and significant differences were found only between the extreme values. The opposite situation was found among three hexaploid species (2n = 42) that can be readily differentiated by significant differences in karyotype parameters Significantly higher intrachromosomal asymmetry indexes in E. erianthus (6x, 2n = 42) and E mendocinus (8x, 2n = 56) indicated relatively larger differences in chromosome size between the genomes of the progenitors of these polyploid species Low variation in the tetraploid species and high variation in the hexaploid and octoploid species were also found in the number and morphology of chromosomes with secondary constrictions (CSCs). Tetraploid species with the genome formula SSHH (S from Pseudoroegneria and H from Hordeum) showed only four CSCs from the S genome of Pseudoroegneria. The presence of CSCs from both S and H genomes in synthetic SSHH tetraploids and in natural SSHHHH hexaploids indicated absence of suppression of nucleolar organizing region (NOR) activity (amphiplasty) between the NORs from the S and H genomes. On the basis of karyotype and molecular data, it was hypothesized that the nucleolar organizing regions from the H genome were eliminated or highly reduced during the evolution of the tetraploid species.
Triticeae
Polyploid
Elymus
Hordeum
Chromosome number
Genome size
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The present study covers chromosome counts, male meiosis and pollen fertility in 164 species of dicots from the Parvati Valley, Kullu district, Himachal Pradesh. Gathered cytological information generates first ever chromosome counts, new diploid/polyploid cytotypes and varied chromosome counts. As many as 41 species (25%) showed intraspecific euploid cytotypes. Role of aneuploidy causing chromosomal variation is apparent from the existence of 71 species (43.29%) depicting aneuploid/dysploid cytotypes at diploid and/or polyploid levels and 114 genera showing dibasic/polybasic nature. The existence of abnormalities in several species resulted in the production of genetically imbalanced and sterile pollen grains. The viable gametes with variable chromosome numbers might have played a part in the origin of aneuploids, polyploids and species complexes. Also the non-viable gametes produced as a consequence of meiotic irregularities might have resulted in reduction of reproductive success of species through seeds. Consequently, the plants have adopted alternate means of propagation through asexual and vegetative modes which is quite prevalent in the plants of area.
Polyploid
Parthenogenesis
Chromosome number
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Agropyron mongolicum Keng, the narrow linear-spiked diploid species (2n = 14), was hybridized with the broad pectinate-spiked diploid (2n = 14), A. cristatum (L.) Gaertner. The F 1 hybrids were all diploids and morphologically intermediate to their parents. Chromosome pairing at metaphase I in the hybrids averaged 1.40 I, 5.59 II, 0.35 III, and 0.09 IV per cell, demonstrating that the two parental genomes are very similar. The F 1 hybrids were partially fertile. The F 2 progeny showed a broad array of variations in spike morphology and chromosome pairing behavior. Cytological data of the F 1 hybrids and the F 2 progeny revealed that these two diploid species contain the same basic P genome but differ by structural rearrangements of some chromosomes. The patterns of multivalent associations were the result of a heterozygous reciprocal translocation between a long and a very short chromosome segment. The colchicine-induced C 0 amphiploids were fully fertile with regular chromosome pairing behavior. These two diploid species are the likely source of morphological variation in the tetraploid crested wheatgrasses.Key words: Agropyron, cytogenetics, chromosome pairing, interspecific hybrids.
Agropyron cristatum
Agropyron
Chromosome pairing
Polyploid
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Citations (19)
Polyploid
Callus
Plant biochemistry
Doubled haploidy
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Triticum aestivum cv. Chinese Spring (2n = 6x = 42, ABD genomes) was crossed with diploid Inner Mongolian Agropyron Gaertn. species A. cristatum and A. mongolicum and reciprocal hybrids between them (2n = 2x = 14, P genome, with or without B chromosomes). Intergeneric hybrids with 2n = 27, 28, 32, and 33 chromosomes were produced by the aid of embryo rescue. The extra chromosomes in two hybrids were assumed to be B chromosomes transmitted by the male Agropyron parent. Average meiotic pairing in the euploid hybrid with 28 chromosomes was 14.38 univalents + 4.92 bivalents + 1.26 trivalents. This level of pairing higher than expected was likely due to homeologous associations between wheat chromosomes. This data indicates that the P genome of diploid as well as tetraploid Agropyron originating from Inner Mongolia possess a genetic system interfering with 5B homoeologous restricting system of wheat.Key words: intergeneric hybrids, Triticum aestivum, diploid Agropyron species, chromosome pairing.
Agropyron cristatum
Agropyron
Elymus
Chromosome pairing
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SUMMARYKaryotypes of some diploid Triticum and Aegilops strains related to polyploid wheats: T. boeoticum and T. urarlu (genome A), Ae. speltoides var. ligustica (genome S), Ae. mutica genome Mt), Ae. bicornis (genome Sb) and Ae. squarrosa (genome D) have been analyzed.Karyotypes of two strains of diploid Triticum analyzed seem to be very similar thus confirming their belonging to the same species. Rather slight differences were found among karyotypes of Ae. speltoides and Ae. mutica, both being quite different from karyotypes presented by Ae. bicornis and Ae. squarrosa. Results obtained seem to ascertain — on a chromosome morphology basis — a higher affinity of Ae. speltoides with Ae. mutica than with Ae. bicornis. Relationships between chromosome morphology of diploid species and Triticum polyploids are rather clear when Ae. squarrosa is considered, while no evident affinities are shown with T. boeoticum and Ae. speltoides (or Ae. bicornis and Ae. mutica).
Polyploid
Aegilops
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Citations (31)