J. M. González

Identification of C-banded chromosomes in meiosis of common wheat, Triticum aestivum L.

SummaryThe C-banding pattern of nine meiotic chromosomes of common wheat (Triticum aestivum L.) as described. In F1s of crosses between monosomics of ‘Chinese Spring’ and two Spanish wheat cultivars, univalent chromosomes were used to aid the recognition and analysis of the C-banding pattern for the individual chromosomes. The identification of one chromosome involved in one translocation in ‘Chinese Spring’ x ‘Pané 247’ has been made through heterochromatin bands observed in the chromosomes involved in multivalents.

The meiotic pairing of nine wheat chromosomes.

SummaryThe meiotic identification of nine pairs of chromosomes at metaphase I of meiosis of Triticum aestivum (B genome, 4A and 7A) has been achieved using a Giemsa C-banding technique. As a result, the analysis of the pairing of each chromosome arm in disomic and monosomic intervarietal hybrids between ‘Chinese Spring’ and the Spanish cultivar ‘Pané 247’ could be carried out. Differences in the chiasmata frequencies per chromosome arm cannot be explained on the basis of relative arm lengths only. Possible effects of arm-to-arm heterochromatic differences on meiotic pairing are discussed.

Meiotic pairing of the amphiploid Hordeum chilense X Triticum turgidum conv. durum studied by means of Giemsa C-banding technique

SummaryThe meiotic behaviour of the amphiploid Hordeum chilense X Triticum turgidum conv. durum using a C-banding staining method is studied. Nine pairs of chromosomes at metaphase-1 (4A, 7A and the seven of the B genome) were identified and the remaining wheat chromosomes (1A, 2A, 3A, 5A and 6A) and seven of the chilense (1 to 7 Hchchromosomes) were assigned to its particular genome. A similar mean number of univalents from parental genomes (wheat and wild barley) were found. No meiotic pairing between chilense and turgidum chromosomes was detected. Differences in the meiotic behaviour per chromosome and amongst genomes are explained on the basis of cytomorphological and heterochromatin characteristics.

Biolistic Transfer of the Gene uidA and Its Expression in Haploid Embryo-like Structures of Triticale (×Triticosecale Wittmack)

Haploid embryo-like structures (ELS) of triticale were obtained by in vitro androgenesis. These structures were bombarded with gold microparticles 1 µm in diameter coated with the plasmid pAHGUS, using the Dupont PDS He/1000 apparatus. Analysis was made of the influence of genotype, duration of ELS pre-culture, helium pressure and shooting distance on the transfer and expression of the gene uidA. No significant differences were seen between genotypes or duration of pre-culture; differences were found, however, with respect to helium pressure and shooting distance. The combination of 1100 psi helium and a 6 cm shooting distance led to the greatest mean number of uidA expression foci in the ELS (1.63), and the greatest mean number of ELS showing at least one focus (0.38). With a pressure of 1800 psi and a 9 cm distance, only 0.35 foci were obtained per ELS, and only 0.18 ELS had one or more foci. These results are being used as references in a program for obtaining double haploid and transgenic triticale plants.

Callus induction and plant regeneration from immature embryos of Brachypodium distachyon with different chromosome numbers

The paper reports the in vitro cultivation of two commercial lines and 23 wild populations (with 10, 20 and 30 chromosomes) of Brachypodium distachyon. Callus induction was assayed on Murashige and Skoog medium containing 1 mg dm−3 2,4-dichlorophenoxyacetic acid (2,4-D) with 30 g dm−3 of sucrose (MSs) or maltose (MSm). No significant differences were seen between the two media with respect to callus induction. Calli were transferred to MSm medium without 2,4-D but containing 0.1 mg dm−3 of 6-benzylaminopurine for plant regeneration. The plant regeneration response was very variable depending on the original induction medium, although no overall preference for one or the other medium was seen. The three main culture stages (callus induction, plant regeneration, and green plantlets formation) are probably differently controlled in the plants with different chromosome numbers. This supports the idea that the three cytotypes of Brachypodium cultured actually belong to different species.

The genetic diversity associated with seed proteins in a collection of Spanish underground vetches (Vicia sativa L. subsp. amphicarpa (Dorthes) Asch. et Graebn.)

The characterization of plant genetic resources is the first step towards improving their use. The Spanish Plant Genetic Resources Centre, which belongs to the National Institute for Agricultural and Food Technology Research (CRF-INIA), conserves accessions of wild underground vetches collected in Spain. In the present work, 26 underground vetch accessions were characterized in terms of their seed storage proteins (separated by SDS-PAGE) as a means of assessing the genetic variation of these plants and their agronomic value. Vicia sativa cv. Vereda was used as control. A total of 54 bands were detected, of which 49 were polymorphic. Fifty eight different electrophoretic patterns were observed in total. Protein bands were scored in terms of their presence (1) or absence (0) for all the seeds studied, and two matrices constructed, one with all the bands present in each accession, the other with the different patterns for each accession. Dendrograms based on the Jaccard similarity index and the UPGMA clustering method were produced from these matrices, and the degree of genetic variation between and within accessions was calculated. The groups obtained were compared with the chromosome number for each accession. The results reflect the great diversity of underground vetch seed storage proteins. The aerial and underground seeds of 16 accessions were then analysed separately. In some cases, the aerial and underground flowers of the same plant produced different proteins.

Metaphase-I analysis of a Triticum aestivum x T. monococcum hybrid by the C-banding technique

SummaryThe meiotic pairing behaviour at metaphase I of a Triticum aestivum×Triticum monococcum hybrid has been studied by means of the C-banding technique to ascertain the homology between the chromosomes in the A genome of the two species. The technique allowed the A and B genome chromosomes and the 2D, 3D and 5D chromosomes to be identified. Differences in the level of chromosome pairing in the A genome were noted. The T. monococcum 4A chromosome did not pair with any of the T. aestivum chromosomes in any of the metaphase I cells analysed. Two reciprocal translocations between the 2B and 2D chromosomes on one side and the 2A and 3D on the other side have been identified. The usefulness of the C-banding technique in the study of chromosome homology among species related to wheat is discussed.

Tyramide Signal Amplification: Fluorescence In Situ Hybridization for Identifying Homoeologous Chromosomes

Tyramide signal amplification (TSA) fluorescence in situ hybridization (FISH) has been shown as a valuable molecular tool for visualizing specific amplified DNA sequences in chromosome preparations. This chapter describes how to perform TSA-FISH, paying special interest to its two critical steps: probe generation and metaphase plate generation. The potential of physically mapping 12S-globulin sequences by TSA-FISH as a means of identifying homeology among chromosome regions of Avena species was tested and is discussed.

Chromosomal location by F1 monosomic analysis of endosperm proteins in bread wheat : 2. Two-dimensional fractionation of gliadins.

SummaryThe gliadin components from four bread wheat cultivars: Chinese Spring, Capelle Desprez, Holdfast and Pane-247 and their monosomic F1s for the chromosomes of homoeologous groups 1 and 6 have been analyzed by two-dimensional (2-pH) polyacrylamide gel electrophoresis. Chromosomal location of gliadin genes and the allelic differences were well established by analyzing the different F1 monosomic hybrids, electrophoretical patterns and differences in relative staining intensity. A new gliadin encoded by a gene located on chromosome 6B in Chinese Spring is described. The two-dimensional patterns of gliadin in the other three varieties and the chromosomal location of their genes are reported for the first time. Relationships between gliadins in the two-dimensional patterns and the traditional system for their nomenclature are discussed.

Partial asynapsis involving specific chromosomes in intervarietal hybrids of Triticum aestivum L.

SummaryMetaphase I chromosome association of the monosomic F1 and the backcross progenies made to develop a monosomic line in the Spanish common wheat Pané-247 was analyzed using a Giemsa C-banding technique. This permits the unequivocal identification of nine meiotic chromosomes (4A, 7A and the seven chromosomes of the B genome). The average frequencies of pairing per arm and of univalents for these nine pairs per arm and of univalents for these nine pairs indicate a difference between arms. The F1 showed asynapsis with univalents in 18.5 per cent of PMCs in intervarietal hybrids. This mainly involved chromosomes 4A, 1B and 6B which also have the largest amount of constitutive heterochromatin. The possible causes of reduced metaphase I association and its rapid decrease during backcrossing are discussed in relation to polymorphism between heterozygous homologous chromosomes.