Chromosome structural changes in cultured celery cells

Chromosome variation in dividing protoplasts and cell suspensions of wheat

The cytology of bread wheat (Triticum aestivum) suspension lines, recycled lines (selected for high division frequency) and their dividing protoplasts, have been examined. Extensive numerical and structural chromosome variation was present in all the lines. The most frequently observed chromosome numbers were around 2n=32, indicating that considerable chromosome loss from the normal wheat complement (2n=6x=42) had occurred during selection of the lines. Chromosome aberrations also indicated loss of chromosome arms and chromosome segments. The implications of this variation for studies on transformation and for the potential regeneration of whole plants from protoplasts of bread wheat are discussed.

Molecular divergence of alfalfa somaclones

Plantlets were regenerated from alfalfa callus following passage through a tissue culture medium which contained gibberellic acid. A proportion of these plantlets showed obvious morphological variations. Leaflet, stem and petiole tissue of these plants were extracted to yield a soluble protein homogenate which was characterized by polyacrylamide gel electrophoresis. Over 18 individual protein bands were resolved and visualized by staining with coomassie blue G250. Electrophoretic gels from regenerated plantlets and from the parent plant were scanned spectrophotometrically and analyzed. The relative quantity of each of the proteins resolved from plants was correlated with proteins of other plants via the Pearson's product-moment correlation. Cluster analysis was then performed using these correlation coefficients to judge relatedness among somaclones and the parent plant. Two of 22 somaclones (9.1%) differed significantly from the parent and from the other somaclones judged by quantitative protein pattern variations. Three distinctive lineages through tissue culture produced plantlets. Using a discriminant analysis strategy somaclones could be grouped according to lineage with 80.8% accuracy based upon distinctions between protein electrophoretic patterns. Two of the somaclone lineage groupings showed no overlap with the parental grouping which indicated significant molecular divergence of these plantlets as judged by quantitative protein differences.

Analysis of fertility in somatic hybrids of Nicotiana rustica and N. tabacum and progeny over two sexual generations

Somatic hybrid plants, produced between Nicotiana rustica and N. tabacum by heterokaryon isolation and culture and also by mutant complementation, were examined regarding their ability to set seed. From a total of seventeen independent somatic hybrids, three were found to be partially self-fertile while the others did not set seed. Differences regarding the methods of hybrid selection, parental varieties and chloroplast composition of hybrids did not appear to be significant regarding the ability of plants to set seed. Much variation in fertility was observed in subsequent generations and by recurrent selection of the most fertile, over two generations, it was possible to increase the level of self-fertility in some of the progeny. One R2 derivative possessed approximately a tenfold higher level of self-fertility than it's somatic hybrid parent. The presence of genetic markers from both parents were observed in all progeny indicating their hybrid nature.

Spontaneous electrophoretic and chromosomal variability in callus cultures and regenerated plants of celery

Reciprocal sexual crosses were performed to produce plants heterozygous at four nuclear loci, two of which coded for phosphoglucomutase (PGM) and shikimic acid dehydrogenase (SDH) isozymes and could be visualized in petiole callus tissue. Clones of one reciprocal always exhibited the heterozygous phenotype at both isozyme loci, but 25.8% of clones of the other exhibited loss of the fast migrating electromorph at the PGM locus while remaining 100% heterozygous at the SDH locus. No reversion to heterozygosity was observed and the variant phenotype was transmitted to regenerated plantlets. All regenerates were karyologically and developmentally abnormal, and studies of the inheritance of this variability were therefore not possible. Epigenetic change, point mutation, and somatic recombination were ruled out as possible causes due to gross incongruencies with the phenomenon. No consistent differences between normal and variant clones were detected with respect to chromosome number, structure, and anomalous disjunction.