Somatic hybrid plants of Nicotiana tabacum (bar) (+) Nicotiana megalosiphon (npt II) were recovered after polyethylene glycol (PEG) mediated fusion. Hybrid calluses were selected on the basis of their dual resistance to bialaphos and kanamycin or UV inactivation of the donor species (Nicotiana megalosiphon) protoplasts. The hybrid nature of the individual clones obtained was confirmed by AFLP analysis. An array of plants were recovered including self-fertile hybrid plants with N. tabacum or N. megalosiphon phenotype, self-sterile plants with N. tabacum habit, leaf and intermediate flower morphology, self-sterile plants with N. megalosiphon habit, abnormal leaves and intermediate flowers, and self-sterile plants of N. megalosiphon type with abnormal characters. Viable pollen was observed in hybrid plants from the third group. The hybrids possessed a nuclear DNA content near that of the diploid tobacco or N. megalosiphon, and also near that of the tetraploid genome size of N. megalosiphon. The results provide evidence for nonpreferential loss of one of the parental genomes and spontaneous asymmetrization of hybrid plants. The present study shows that by means of somatic hybridization a great genetic diversity in the hybrid clones can be achieved.
Anthers of 10 alfalfa (Medicago sativa L.) lines were used as initial material for the production of androgenic haploids. More than 30 variants of nutrient media were tested. Twenty five different treatments with low temperatures and gamma rays were tried in order to find optimal conditions for callus induction and organogenesis.The genotype, stage of microspore development, phytohormonal composition of the nutrient media and pretreatment with physical agents, alone or in combination, affected the efficiency of organogenesis and regeneration in anther cultures of alfalfa.Plants exhibited a high degree of variability in their chromosome number. Haploids, dihaploids and mixoploids were obtained.Cytological studies of in vitro pollen development revealed the origin of the regenerants from microspores.
We present data on the morphological, cytological, biochemical and genetic characteristics of tomato regenerants obtained through anther culture. As a result of induced androgenesis, more than 6,000 rooted regenerants were developed that differed both from the donor plants and among each other with respect to habitus and leaf, flower and inflorescence morphology. Cytological analysis revealed a great variability in chromosome number in the cells of the regenerated plants. While most of the regenerants were mixoploid, the majority of the cells had a haploid chromosome number. R(1) and R(2) progenies were tested for their resistance to Clavibacter michiganense subsp. michiganense ( Cmm 7). Some of the regenerants were resistant to the pathogen. A biochemical analysis of fruit from R(3) and R(4) plants showed a higher content of dry matter, sugars and vitamin C in the regenerant plants obtained from the hybrids than in those from the cultivars and control plants. The values of the parameters of hybrid regenerants grown in the greenhouse were about 1.5-fold higher than those of the hybrid regenerants grown in the field, and this trend is clearly expressed in all of the hybrid regenerants. The results obtained suggest that induced androgenesis and gametoclonal variation may be used as an additional tool to create a large range of new forms. The application of the latter in breeding programs would accelerate the development of tomato lines and varieties that would be more productive, disease-resistant, highly nutritive and flavour-acceptable.
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