Spontaneous extensive chromosome elimination in somatic hybrids between somatically congruent species Nicotiana tabacum L. and Atropa belladonna L.

Summary Mesophyll protoplasts of the kanamycin-resistant nightshade, Atropa belladonna, were fused with mesophyll protoplasts of the phosphinothricin resistant-tobacco, Nicotiana tabacum. A total of 447 colonies resistant to both inhibitors was selected. Most of them regenerated shoots with morphology similar to one of the earlier obtained and described symmetric somatic hybrids Nicotiana + Atropa. However, three colonies (0.2%) regenerated vigorously growing tobacco-like shoots; they readily rooted, and after transfer to soil, developed into normal, fertile plants. Unlike their tobacco parental line, BarD, the obtained plants are resistant to kanamycin [they root normally in the presence of kanamycin (200 mg/1)] and possess activity of neomycin phosphotransferase (NPT II) with the same electrophoretic mobility as the one of the nightshade line. According to Southern blot hybridization analysis carried out with the use of radioactively labeled cloned fragments of the Citrus lemon ribosomal DNA repeat, as well as with Nicotiana plumbaginifolia genus-specific, interspersed repeat Inp, the kanamycin-resistant plants under investigation have only species-specific hybridizing bands from tobacco. Cytological analysis of the chromosome sets shows that plants of all three lines possess 48 large chromosomes similar to Nicotiana tabacum ones (2n = 48), and one small extra chromosome (chromosome fragment) similar to Atropa belladonna ones (2n = 72). Available data allow the conclusion that highly asymmetric, normal fertile somatic hybrids with a whole diploid Nicotiana tabacum genome and only part (not more than 2.8%) of an Atropa belladonna genome have been obtained without any pretreatment of a donor genome, although both these species are somatically congruent.     

Production and cytogenetic analysis of BC1, BC2, and BC3 progenies of an intergeneric hybrid between Triticum aestivum (L.) Thell. and tetraploid Agropyron cristatum (L.) Gaertn.

Summary Intergeneric hybrids between Triticum aestivum cv Chinese Spring and Agropyron cristatum 4x (2n= 5x=35, ABDPP genomes) with a high level of homoeologous meiotic pairing between the wheat chromosomes were backcrossed 3 times to wheat. Pollination of the F₁ hybrid with Chinese Spring resulted in 22 BC₁ seeds with an average seed set of 1.52%. Five BC₁ plants with 39–41 chromosomes were raised using embryo rescue techniques. Chromosome pairing in the BC₁ was characterized by a high frequency of multivalent associations, but in spite of this there was no evidence of homoeologous pairing between chromosomes of wheat and those of Agropyron. All of the plants were self sterile. The embryo rescue technique was again essential to produce 39 BC₂ plants with chromosome numbers ranging from 37 to 67. The phenomenon of meiotic non-reduction was also observed in the BC₃ progenies. In this generation male and female fertility greatly increased, and meiotic pairing was fairly regular. Some monosomic (2n=43) and double monosomic (2n=44) lines were produced. Analysis of these progenies should permit the extraction of the seven possible wheat-Agropyron disomic addition lines including those with the added chromosomes carrying the genes involved in meiotic non-reduction and in suppression of Ph activity.     

Monosomic and double monosomic substitutions of Hordeum bulbosum L. chromosomes into H. vulgare L.

Summary One of the aims of the interspecific crossing programme between Hordeum vulgare L. and H. bulbosum L. has been to introgress desirable genes into barley from the wild species. However, despite their close taxonomic relationship there have been few reports of achieving this objective using amphidiploid hybrids. In order to broaden the range of available hybrids, partially fertile triploids between H. vulgare (2n = 2x = 14) and H. bulbosum (2n = 4x = 28) were developed and crossed with H. vulgare as female parent. From 580 progeny which were screened, eight putative single monosomic chromosome substitution lines and one double monosomic substitution were identified by cytological analysis. These involved the substitution of H. vulgare chromosome 1 (two lines), 6 (four lines), 6L (one line), 7 (one line) and 1 + 4 (one line) by their respective H. bulbosum homoeologues. The H. bulbosum chromosome was frequently eliminated during plant development, but it was observed regularly in pollen mother cells of two lines. However, pairing between the H. bulbosum chromosome and its H. vulgare homoeologue was low. Several of the lines were more resistant than their H. vulgare parents to powdery mildew (Erysiphe graminis DC. f.sp. hordei Em. Marchai), net blotch (Drechslera teres Sacc.) and scald (Rhynchosporium secalis (Oudem.) Davis). Apart from their use in studying genome relationships, their value to plant breeders will depend on the ease of inducing translocations between the parental chromosomes.     

Effect of radiation dose on the production of and the extent of asymmetry in tomato asymmetric somatic hybrids

Summary Asymmetric somatic hybrids were recovered following fusion of tomato leaf mesophyll protoplasts with irradiated protoplasts isolated from Lycopersicon pennellii suspension cells. The asymmetry was determined by scoring the regenerants at between 20 and 24 loci using isozymes and restriction fragment length polymorphisms. In addition, three quantitative traits, fruit size, leaf shape, and stigma exsertion, were measured in the regenerants. The recovery of asymmetric somatic hybrids was as high as 50% of the regenerants, and there was no requirement for the transfer of a selectable marker gene from the irradiated partner. The amount of nuclear DNA transferred from the irradiated protoplast fusion partner was found to be inversely proportional to the radiation dose. It was possible to recover tomato asymmetric somatic hybrids which were self-fertile and contained limited amounts of genetic information from L. pennelli.     

Chromosomal and isozyme studies of Nicotiana tabacum — Glycine max hybrid cell lines

Summary The chromosomal stability of a number of somatic hybrids derived from soybean (Glycine max (L.) Merr.) and Nicotiana tabacum var. Xanthi were investigated. Several of the hybrid cell lines retained more than half the complement of N. tabacum chromosomes after 7 months of culturing. A number of chromosomal abnormalities were observed. The hybrids were positively identified by employing isozyme analysis of several dehydrogenases and aspartate aminotransferase.NRCC No. 20130     

Hybridization between tetraploid species of Alopecurus L. (Poaceae): chromosome behaviour of natural and artificial hybrids

The meiotic behaviour of plants from mixed populations of Alopecurus pratensis × A. geniculatus and of A. pratensis × A. arundinaceus ( 2n = 4×(= 28) is reported together with observations on some artificially produced hybrids. This meiotic behaviour is correlated with the degree of hybridity as shown by the hybrid index values of the plant. In A. pratensis × A. geniculatus hybrids there are marked differences between populations in the degree of meiotic disturbance and in one population there was an almost complete breakdown of meiosis. Alopecurus pratensis × A. arundinaceus hybrids show fairly regular meiotic pairing but in most plants there are a few univalent chromosomes at metaphase I. Artificially produced hybrids of A. pratensis × A. aequalis gave meiotic configurations that suggest that the genomes of the parent species are very similar. Taken together with the results from artificially produced hybrids of A. pratensis × A. geniculatus , it is suggested that bivalent-promoting mechanisms reduce multivalent formation both in the species and the hybrids. The interaction of different genotypes involved in the control of meiosis may account for the variation in meiotic behaviour in the different populations of hybrids. Pollen fertility is reduced in most populations of hybrids and likely to be an important factor permitting introgressive hybridization.     

Successful crosses between Festuca arundinacea Schreb. and Dactylis glomerata L.

Summary Five F₁ plants have been obtained after extensive crossing between different ecotypes or varieties of Festuca arundinacea Schreb. and Dactylis glomerata L. The success did not appear to depend on specific treatments (spraying with -aminocaproic acid or gibberellic acid or pre-pollination with killed pollen from the seed parent), but the crossability is limited to exceptional plants.F₁ hybrids showed characteristics of both the parents. In four hybrids various developmental disturbances were observed (low viability, aneusomaty, absence of development of inflorescences). Only one hybrid consistently showed 2n=35 chromosomes, good viability and growth, however, it was sterile. After clonal propagation, attempts for polyploidization were started.     

Unusual base sequence arrangement in phage phi 29 DNA.

Susceptibility of Bacillus subtilis phage phi 29 DNA to 34 different restriction endoculceases was determined. Three enzymes, BglI, XbaI and BstEII, were found to cleave phi 29 DNA only once at specific sites. The sites of these single cleavages have been mapped. Thirteen enzymes did not cut phi 29 DNA. phi 29 HindIII DNA fragments inserted into pBR313 plasmid and propagated in Escherichia coli, were resistant to these restriction endonucleases. This result suggests that the insusceptibility is due to the absence of the nucleotide sequences on phi 29 recognized by the enzymes, and not to the presence of modified nucleotides.     

Inheritance and linkage analysis of five enzyme loci in interspecific hybrids of toadlets,genus Bombina

Progeny produced from Bombina bombina, B. variegata, and field-collected interspecific hybrids have been analyzed for the inheritance of five enzyme loci, which are fixed for alternate alleles in the parental species. Lactate dehydrogenase (Ldh-1), NAD-dependent malate dehydrogenase (Mdh-1), creatine kinase (Ck), adenylate kinase (Ak), and glucosephosphate isomerase (Gpi) are all inherited in a Mendelian manner as codominant alleles at nuclear loci. Both parental alleles are equally functional in artificial F₁ hybrids (female B. bombina×male B. variegata) at each of the loci studied. No linkage between any pair of loci was observed. Discovery of this inherited biochemical variation combined with a technique for assaying individual genotypes without killing the animals makes feasible studies of hybrid population structure heretofore impossible.This work was partly supported by the Polish Academy of Sciences within the project MR-II/6.