It is concluded from a review of the literature that plant cell culture itself generates genetic variability (somaclonal variation). Extensive examples are discussed of such variation in culture subclones and in regenerated plants (somaclones). A number of possible mechanisms for the origin of this phenomenon are considered. It is argued that this variation already is proving to be of significance for plant improvement. In particular the phenomenon may be employed to enhance the exchange required in sexual hybrids for the introgression of desirable alien genes into a crop species. It may also be used to generate variants of a commercial cultivar in high frequency without hybridizing to other genotypes.

Somaclonal variation — a novel source of variability from cell cultures for plant improvement

This invention is directed to the production of plants, plant tissues and seeds which are resistant to inhibition by an herbicide which normally inhibits the growth and development of those plants, plant tissues and plant seeds. In particular this invention is directed to altered acetohydroxyacid synthase enzymes which are resistant to inhibition by herbicides which normally inhibit the activity of the synthase before such alteration. This invention further relates to genes encoding such enzymes, and to processes for utilizing these novel genes and enzymes. Further products of the invention include plants, plant tissues and seeds which exhibit resistance to such herbicides resulting from expression of genes encoding herbicide resistant acetohydroxyacid synthase enzyme.

Herbicide resistance in plants

Protoplasts of Nicotiana tabacum SRI (streptomycin resistant) and of Nicotiana knightiana (streptomycin sensitive) were fused using polyethylene glycol treatment. From three heterokaryons 500 clones were obtained. From the 43 which were further investigated, 6 resistant, 3 sensitive, and 34 chimeric (consisting of resistant and sensitive sectors) calli were found. From eight clones, a total of 39 plants were regenerated and identified as somatic hybrids. Chloroplast type (N. tabacum = NT or N. knightiana = NK) in the plants was determined on the basis of the species specific EcoRI restriction pattern of the chloroplast DNA. Regenerates contained NT (13 plants) or NK (15 plants) plastids but only the plants with the NT chloroplasts were resistant to streptomycin. This finding and our earlier data on uniparental inheritance points to the chloroplasts as the carriers of the streptomycin resistance factor.

Streptomycin resistant and sensitive somatic hybrids of Nicotiana tabacum + Nicotiana knightiana: correlation of resistance to N. tabacum plastids

Gene manipulation in plant improvement , Gene manipulation in plant improvement , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Gene manipulation in plant improvement

Elimination of plastids during spermatogenesis and fertilization in the plant kingdom.

Diploid callus cultures from four genetic lines of tobacco (Nicotiana tabacum) were grown in the presence of 0–2 mg/ml streptomycin sulfate. These genetic lines are closely related with regard to nuclear genes, but differ in their respective cytoplasmic genomes. In calli from all these four lines, the formation of green color was inhibited at 0.5 mg/ml streptomycin. Small differences were observed between the four lines in their respective growth on medium containing streptomycin. Streptomycin resistant mutants were isolated from cultures at high drug concentrations, using as criteria for isolation either the ability of the callus to grow green, or a better rate of growth as indicated by the size of white callus.

Nakdimon Umiel

Papers

Effects of streptomycin on diploid tobacco callus cultures and the isolation of resistant mutants

Effects of sugar concentrations on growth greening and shoot formation in callus cultures from four genetic lines of tobacco

Streptomycin Resistance in Tobacco: III. A Test on Germinating Seedlings indicates Cytoplasmic Inheritance in the St-R701 Mutant

Development of tobacco seedlings and callus cultures in the presence of amitrole

The Growth of Carrot Callus Cultures at Various Concentrations and Composition of Saline Water