J. R. Lacadena

Evidence for wheat-rye nucleolar competition (amphiplasty) in triticale by silver-staining procedure.

SummaryAmphiplasty in hexaploid triticale, the artificial amphiploid of tetraploid wheat and diploid rye, is analyzed for the first time using a modified, highly reproducible, silver-staining procedure. A comparative analysis of metaphase somatic cells by phase contrast, C-banding and silver-staining of the hexaploid triticale cv. ‘Cachirulo’ and its parents, namely, the tetraploid durum wheat cv. ‘Enano de Andujar’ and the diploid rye cv. ‘Petkus’ has been made. Two silver-stained nucleolar organizer regions (Ag-NORs) (the chromosome pair 1 R) are observed in all rye plants analyzed, whereas four Ag-NORs (chromosome pairs 1 B and 6 B) are found both in the tetraploid wheat parent and in the triticale. The rye Ag-NORs are absent in the triticale. Since the Agstaining reaction of NORs can be considered as an indication for genetic activity, the silver procedure can be used to visualize gene functionality at the rDNA sites with conventional light microscopy and, consequently, the modified Ag-staining method described can be very useful in analyzing the amphiplasty phenomenon in natural or artificial hybrid combinations and derivatives in the Triticum group and its relatives.

Nucleolar organizer activity in wheat, rye and derivatives analyzed by a silver-staining procedure

Nucleolar activity was analyzed in wheat (Triticum sp.), rye (Secale cereale) and several types of wheat-rye derivatives using a modified, highly reproducible, silver staining procedure (Lacadena et al. 1984). A comparative analysis of the nucleolar organizer regions (NORs) of somatic metaphase chromosomes was made by phase contrast, C-banding, and silver staining. The frequency distribution of the number of nucleoli visualized at interphase by silver staining was also used to infer the activity of NORs. The results agree quite well with data from in situ hybridization reported by other authors. The behavior of euploid, ditelosomic and nulli-tetrasomic plants of common wheat showed the relative nucleolar activity of the four organizer chromosomes to be: 6B > 1B > 5D > 1A. — Several types of wheat-rye derivatives were analyzed: interspecific hybrid, triticale, addition and substitution lines, and plants with the genome constitutions, AABBDR, ABDR + 5D, ABRR, and ABRRR. In all cases the nucleolar organizer chromosome 1R of rye was suppressed by the presence of wheat chromosomes.

Nucleolar activity and competition (Amphiplasty) in the genus Aegilops

SummaryNucleolar activity and competition (amphiplasty) has been analysed in diploid, tetraploid and hexaploid species of Aegilops using a highly reproducible silver-staining procedure. A comparative analysis of somatic metaphase chromosomes by phase contrast, C-banding and Ag-staining was made to analyse the activity of the nucleolar organiser regions (NORs). With the exception of Ae. crassa 4x, amphiplasty occurs in all the tetraploid and hexaploid species analysed. The U genome from Ae. umbellulata suppresses completely the NOR activity of the genomes M° (Ae. ovata), Sv (Ae. variabilis), D (Ae. juvenalis) and C (Ae. triuncialis) and that of one pair of the nucleolar organiser chromosomes of the genomes Mc (Ae. columnaris), Mb (Ae. biuncialis), Mj (Ae. juvenalis) and Mt (Ae. triaristata 6×). The nucleolar activity of the D genome is completely suppressed by the genomes U (Ae. umbellulata), C (Ae. cylindrica) and Mv (Ae. ventricosa).

C-banding pattern and meiotic pairing in five rye chromosomes of hexaploid triticale.

SummaryThe meiotic behaviour of rye chromosomes 1R, 2R, 3R, 6R and 7R/4R of hexaploid triticale ‘Cachirulo’ is analyzed using the C-banding technique. These chromosomes show different C-banding patterns and present different pairing levels at metaphase I. A decreasing effect of large telomeric heterochromatin bands on pairing is deduced from the following two main facts: i) The chromosome 7R/4R shows the highest pairing associated with the smallest amount of heterochromatin, ii) pairing levels of 2 R short arm and 3 R long arm which carry large telomeric bands are less than their respective long and short arms lacking telomeric heterochromatin. Possible desynaptic effects of heterochromatin are discussed although an asynaptic effect cannot be rejected.

Maintenance of interchange heterozygosity in cultivated rye, Secale cereale L.

SummaryThe maintenance for several generations of interchange heterozygosity in both experimental and cultivated fields of rye is analysed. An experimental analysis of interchange heterozygotes has been carried out to ascertain whether only one or several translocations exist in the population. Interchange heterozygosity is discussed on the basis of the karyotypic orthoselection model. The maintenance of a constant frequency (20 per cent) of structural heterozygotes for several generations suggests the existence of an equilibrium. The possible mechanisms involved in such an equilibrium are discussed.

Analysis of nucleolar activity in Agropyron elongatum, its amphiploid with Triticum aestivum and the chromosome addition lines

SummaryThe nucleolar organizer activity of the Agropyron elongatum, its amphiploid with hexaploid wheat (Triticum aestivum) and the chromosome addition lines is analyzed by the silver-staining procedure. Four Ag-NORs are observed in A. elongatum corresponding to the chromosomes 6E and 7E. In the amphiploid T. aestivum — A. elongatum, eight Ag-NORs are observed which corresponds the wheat chromosomes 1B and 6B and to the elongatum chromosomes 6E and 7E. Thus, there is codominance in the nucleolar organizer activity of the chromosomes of the two species. However, a partial amphiplasty is detected since less than 8 Ag-NORs (7 up to 4) are observed in some metaphase cells; the chromosomes 6E and 7E are occasionally suppressed by wheat chromosomes. This conclusion is confirmed by the behaviour of the addition lines since only in those corresponding to the chromosomes 6E and 7E are the elongatum chromosomes nucleolar active although occasionally they can be suppressed by wheat chromosomes.

Cytogenetic structure of common wheat cultivars from or introduced into Spain

SummaryChromosome arrangements of twenty-eight cultivars of common wheat, Triticum aestivum L., from or introduced into Spain are compared with that of ‘Chinese Spring’ taken as a pattern. All the cultivars analyzed differ from ‘Chinese Spring’ by one or two reciprocal translocations. When 12 out of 28 cultivars were compared it was concluded that a minimum number of thirteen interchanges are present, involving at least ten different chromosomes of the complement. The interest of a reappraisal of the rôle of interchanges in the evolution of Gramineae is pointed out.

Nucleolus organizer competition in Triticum aestivum - Aegilops umbellulata chromosome addition lines.

SummaryThe nucleolar organizer activity of wheat (Triticum aestivum, AABBDD) and Aegilops umbellulata (UU) chromosomes have been analyzed in the complete set of the chromosome addition lines by using a highly reproducible silver-staining procedure. Chromosomes 1U and 5U produce the partial inactivation of wheat nucleolar organizer chromosomes 6B, 1B and 5D. The chromosomes D and G from Ae. umbellulata, which are not SAT-chromosomes, seem to specifically influence the activity of wheat NORs. The predominant status of the U genome with respect to nucleolar competition in the Triticeae is confirmed.

Nucleolar organiser activity in wheat-barley chromosome addition lines

SummaryThe nucleolar organiser activity of cultivated barley, Hordeum vulgare and the wheat-barley chromosome addition lines is analysed by a modified, highly reproducible, silver-staining procedure. Four Ag-NORs are observed in metaphase cells of barley corresponding to chromosomes 5HV and 6HV. Six Ag-NORs are detected in the chromosome addition lines 5HV and 6HV while only four Ag-NORs are observed in the rest of the addition lines analysed (2HV, 3HV, 4HV and 7HV). It is concluded that the nucleolar organiser chromosomes 1B1, 6B1, 5HV and 6HV are active. The chromosome 6HV of barley seems to control the nucleolar activity of its homoeologous 6B of wheat judging from the diminution of the Ag-NOR size of chromosome 6B in the corresponding addition line.

Identification of two chromosomal interchanges in CV. Canaleja of common wheat, Triticum aestivum L.

SummaryTwo independent reciprocal translocations in the Spanish cultivar Canaleja of common wheat, Triticum aestivum L., are identified as 5B–7B and 3A-3D when compared with ‘Chinese Spring’. The translocated segments of the chromosomes 5B and 7B are much longer than those of the chromosomes 4A and 3D. The origin of the 5B–7B interchange ‘Canaleja’ and several other cultivars analyzed by different authors is presumptively traced back to cv. Prince Albert.