Ib Linde-Laursen

Elimination and duplication of particular Hordeum vulgare chromosomes in aneuploid interspecific Hordeum hybrids

SummarySeeds formed in crosses Hordeum lechleri (6x) x H. vulgare (2x and 4x), H. arizonicum (6x) x H. v. (2x), H. parodii (6x) x H. v. (2x), and H. tetraploidum (4x) x H. v. (2x) produced plants at high or rather high frequencies through embryo rescue. Giemsa C-banding patterns were used to analyze chromosomal constitutions and chromosomal locations on the methaphase plate. Among 100 plants obtained from H. vulgare (2x) crosses, 32 plants were aneuploid with 2n=29 (1), 28 (3), 27 (13), 26 (5), 25 (4), 24 (4), or 22 (2); 50 were euploid (12 analyzed), and 18 were polyhaploid (5 analyzed). Four plants had two sectors differing in chromosome number. Two of four hybrids with H. vulgare (4x) were euploid and two were aneuploid. Parental genomes were concentrically arranged with that of H. vulgare always found closest to the metaphase centre. Many plants showed a certain level of intraplant variation in chromosome numbers. Except for one H. vulgare (4x) hybrids, this variation was restricted to peripherally located non-H. vulgare genomes. This may reflect a less firm attachment of the chromosomes from these genomes to the spindle. Interplant variation in chromosome numbers was due to the permanent elimination or, far less common, duplication of the centrally located H. vulgare chromosomes in all 34 aneuploids, and in a few also to loss/gain of non-H, vulgare chromosomes. This selective elimination of chromosomes of the centrally located genome contrasts conditions found in diploid interspecific hybrids, which eliminate the peripherally located genome. The difference is attributed to changed “genomic ratios’. Derivatives of various H. vulgare lines were differently distributed among euploid hybrids, aneuploids, and polyhaploids. Chromosomal constitutions of hypoploid hybrids revealed a preferential elimination of H. vulgare chromosomes 1, 5, 6, and 7, but did not support the idea that H. vulgare chromosomes should be lost in a specific order. H. vulgare SAT-chromosomes 6 and 7 showed nucleolar dominance. Aneuploidy is ascribed to the same chromosome elimination mechanism that produces haploids in cross-combinations with H. vulgare (2x). The findings have implications for the utilization of interspecific Hordeum hybrids.

Haploid barley from the intergeneric cross Hordeum vulgare x Psathyrostachys fragilis

SummaryThe intergeneric hybrid Hordeum vulgare x Psathyrostachys fragilis was fairly easily obtained. During each growing season the intermediate, perennial hybrid yielded haploid tillers of H. vulgare. Late in one season few, hybrid tillers headed. The morphology, cytology and enzymatic patterns of hybrid and haploid tillers were investigated.

Comparison of the Giemsa C-banded and N-banded karyotypes of twoElymus species,E. dentatus andE. glaucescens (Poaceae: Triticeae)

The karyotypes ofElymus dentatus from Kashmir andE. glaucescens from Tierra del Fuego, both carrying genomesS andH, were investigated by C- and N-banding. Both taxa had 2n = 4x = 28. The karyotype ofE. dentatus was symmetrical with large chromosomes. It had 18 metacentric, four submetacentric and six satellited chromosomes. The karyotype ofE. glaucescens resembled that ofE. dentatus, but a satellited chromosome pair was replaced by a morphologically similar, non-satellited pair. The C-banding patterns of both species had from one to five conspicuous and a few inconspicuous bands per chromosome. N-banding differentiated the chromosomes of the constituent genomes by producing bands in theH genome only. TheS genomes of both species were similar with five metacentric and two satellited chromosomes having most conspicuous C-bands at telomeric and distal positions. They resembled theS genome of the genusPseudoroegneria. TheH genomes had four similar metacentric and two submetacentric chromosomes. The seventhH genome chromosome ofE. dentatus was satellited, that ofE. glaucescens nonsatellited, but otherwise morphologically similar. The C-bands were distributed at no preferential positions. TheH genome ofE. dentatus resembles theH genomes of some diploidHordeum taxa.

Giemsa C-banded karyotypes of diploid and tetraploid Hordeum bulbosum (Poaceae).

The similar-looking basic genomes ofHordeum bulbosum (2x and 4x) have five rather similar metacentric, one submetacentric, and one satellited choromosome. C-banding patterns are characterized by one or two centromeric, or juxtacentromeric, small to larger bands in most chromosomes, by bands at the nucleolar organizers, by small or very small telomeric bands, and by the nearly complete lack of intercalary bands. Banding pattern polymorphism is widespread. Banding patterns supported by chromosome morphology enable identification of homologues, and discrimination between non-homologues inH. bulbosum (2x). The C-banded karyotype ofH. bulbosum (4x) supports an autopolyploid origin, but it was possible to identify only homologues of submetacentrics and SAT-chromosomes.

Comparison of the karyotypes ofPsathyrostachys juncea andP. huashanica (Poaceae) studied by banding techniques

The karyotypes ofP. juncea (Elymus junceus) andP. huashanica (both outbreeders) were investigated by Feulgen-staining and by C-, N-, and Agbanding, based on a single plant in cach case. Both species have 2n=2x=14 and large chromosomes, possibly a generic character. The karyotype ofP. juncea has 8 metacentrics and 6 SAT-chromosomes with minute, heterochromatic satellites while that ofP. huashanica has 9 metacentrics and 5 SAT-chromosomes only, 2 of which with small, heterochromatic satellites. The C-banding patterns ofP. juncea chromosomes comprise from one to five, mostly small, bands at distal, and terminal positions, while those ofP. huashanica chromosomes are characterized by large telomeric bands in most arms. Banding patterns and chromosome morphology allow identification of the homologues of the seven chromosome pairs inP. juncea, but of two pairs inP. huashanica only. The patterns of both taxa are polymorphic, supporting that both taxa are outbreeders. The karyotypic characters suggest thatP. juncea is more closely related toP. fragilis than either is toP. huashanica. N-banding stains weakly. Silver nitrate staining demonstrates that nucleolus organizers of both species have different nucleolus forming capacities. The presence of micronucleoli suggests that both species have an extra unidentified chromosome with nucleolus forming capacity.

Giemsa C-banded karyotypes of two subspecies ofHordeum brevisubulatum from China

C-banding patterns ofH. brevisubulatum subsp.brevisubulatum (2x) and subsp.turkestanicum (4x) had conspicuous telomeric C-bands in at least one chromosome arm with a minor difference in average band size between subspecies. Other conspicuous bands were few in number as in other taxa of the species complex. The C-banded area of the chromosomes was estimated to be 7 to 8 and 6 per cent, respectively. C-banding- and SAT-chromosome polymorphisms were observed in both subspecies. The latter and previous observations indicate that the number of SAT-chromosomes is a less reliable diagnostic character. Nucleolar organizer region polymorphisms were demonstrated through silver nitrate staining of nucleoli. C-banding patterns corroborated that tetra- and hexaploid cytotypes of subsp.turkestanicum form an autopolyploid series. Reliable identification ofH. brevisubulatum taxa based on cytological criteria should include the simultaneous use of C-banding patterns, and number and morphology of marker chromosomes.

Genome and chromosome disposition at somatic metaphase in a Hordeum × Psathyrostachys hybrid

The distribution of chromosomes by centromeres and telomeres was studied in 100 squashed, somatic metaphases of a Hordeum vulgare (2n=2x=14) × Psathyrostachys fragilis (2n=2x=14) hybrid. The chromosomes and chromosome arms were individually identified in each of the parental genomes by their Giemsa C-banding patterns. The P. fragilis chromosomes were more widely scattered on the metaphase plate, and were therefore, also, on average located further from the cell centre than the H. vulgare chromosomes. Within the parental genomes, the only exception from a random distribution of the chromosomes was that the two satellited chromosomes of H. vulgare were located closer to each other and to the cell centre than can be attributed to chance. This association was most clearly expressed for the telomeres of the chromosome arms carrying the satellites. The data suggest that the parental chromosome complements constitute separate units. This was supported by the observation that five cells had their genomes arranged side-by-side.

The chromosome complement of Erysiphe graminis f.sp. hordei analysed by light microscopy and field inversion gel electrophoresis

Light microscopy studies of somatic barley powdery mildew fungal cells at metaphase revealed seven to eight chromosomes of at least three different sizes. Separation of fungal chromosomal DNA by field inversion gel electrophoresis (FIGE) was achieved using a combination of very short and long pulses. FIGE showed distinct bands representing chromosomal DNA, mitochondrial DNA and extrachromosomal plasmid DNA. By combining the results from the two techniques used, the haploid genome of the barley powdery mildew fungus is found to contain five very small chromosomes (0·2–0·8 Mb) and a group of at least two larger chromosomes.

Complex interspecific hybridization in barley (Hordeum vulgare L.) and the possible occurrence of apomixis

SummarySeveral complex hybrids were produced from the combination [(Hordeum lechleri, 6x xH. procerum, 6 x) × H. vulgare, 2 x]. Crosses with six diploid barley lines resulted in triple hybrids, most of which had a full complement of barley chromosomes (no. 1–7), but were mixoploid with respect to alien chromosomes (19–22). In one combination, chromosome no. 7 was duplicated. Meiosis in triple hybrids showed low, but variable pairing (1.3–5.5 chiasmata per cell). The syndesis probably did not include the barley chromosomes. Direct back-crosses to di- and tetraploid barley lines were unsuccessful. Chromosome doubling of the triple hybrid based on cv ‘Pallas’ resulted in a plant with 2n = 53–56, which had an increased fertility. Backcrosses to one di- and one tetraploid barley line resulted in offspring. The cross made with the tetraploid line (‘Haisa II’), produced a 28-chromosomic plant in which the male parental genome was absent. We suspect that this plant may have arisen through parthenogenetic development of a reduced female gamete. The other cross with a diploid line (‘9208/9’) resulted in plant with 2n = 51–53. The most likely explanation for this second plant is that an unreduced gamete from the amphiploid was fertilized by a normal gamete from the backcross parent, and during early embryo development, some chromosomes were eliminated.

Intergeneric hybridization and C-banding patterns in Hordelymus ( Triticeae, Poaceae)

Crosses ofHordelymus europaeus (2n = 4x = 28) with four genera in theTriticeae were attempted. Adult hybrids were obtained in combinations withHordeum bogdanii (2x),Hordeum depressum (4x), andSecale cereale (2x). The meiotic pairing was very low in the hybrids withH. bogdanii andSecale cereale (0.12 and 0.30 chiasmata/cell, respectively), whereas high pairing (9.90 chiasmata/cell) was found in hybrids withH. depressum due to autosyndetic pairing ofH. depressum chromosomes. The chromosome complement ofHordelymus europaeus comprised 16 metacentrics, 8 submetacentrics, and 4 SAT-chromosomes. The Giemsa C-banding patterns of the chromosomes were characterized by small to minute bands at no preferential positions. It is hypothesized thatHordelymus europaeus may genomically be closest related toTaeniatherum andPsathyrostachys spp.