Abstract
Doubling the chromosome number of diploid and haploid Echinacea purpurea plants have high applicable values for genetic improvements of the crop. Field experiments have shown that the tetraploid plants grow vigorously as compared to diploid plants. Tissue culture methodology provides a useful way to separate plant chimeras into their component genotypes. In general, mutated cells are difficult to monitor but mutations which result in a change in genome chromosome number are an exception, because chromosome number mutation can be identified by chromosome counting. In the present study, chimeric materials were used as explant source, and higher percentages of tetraploid shoots were induced from explants with higher ratio of tetraploid cells to diploid cells; explants possessing 26% tetraploid cells regenerated 10% tetraploid plants, explants possessing 15% tetraploid cells regenerated 4% tetraploid plants, and explants possessing 11% tetraploid cells regenerated 2% tetraploid plants. The reliability of the tetraploid nature of the regenerated plants, directly from colchicine treated culture and from chimeric materials was confirmed by regenerating buds again from explants of these plants, and amongst the six plants tested, five were confirmed to be true tetraploids that regenerated 100% tetraploid plants, and the rest one to be a chimera which regenerated 93% tetraploid plants. Results of the experiments indicate that in vitro culture method could provide a useful way to separate chimeras into individuals with one of the component cell genome numbers, and by this it could produce 100% pure tetraploids from chimera plants for further genetic studies of Echinacea purpurea L and for direct agricultural application. Key words: Breeding; Chimera; Chromosome; Purple coneflower; Regeneration; Tissue culture DOI: http://dx.doi.org/10.4038/tare.v13i1.3131 Tropical Agricultural Research and Extension 13(1) 2010 pp.11-15
Highlights
Echinacea purpurea (Asteracea) has a deserved reputation for enhancing the human immune system (Barnes et al 2005)
Chimeric plants with 10.9% and 15.0% tetraploid cells generated lower percentages of tetraploids, 2% and 4%, respectively where were no tetraploid plants observed from chimeric plant materials which possessed lower percentages of tetraploid cells of no more than 4%
As a number of mixoploids had been identified in our early experiments, we considered it possible to obtain pure tetraploids from these mixoploids by regenerating shoots from tetraploid cells of chimeric petiole explants
Summary
Echinacea purpurea (Asteracea) has a deserved reputation for enhancing the human immune system (Barnes et al 2005). Chimeras may arise when cells undergo mutations. These mutations could occur spontaneously or as a result of induced irradiation or treatment with chemical mutagens. Many ornamental plants with variegated leaves are chimeras, with the outer layer lacking chlorophyll. Separation of the chimera into component genotypes has been observed in Ananas comosus (Jones et al 1974) and Dracaena marginata “Tricolor” (Chua et al 1981). This paper describes the production of tetraploid and diploid E. purpurea using mixoploid plants as starting material and the reliability of tetraploids which are directly produced by colchicine treatment or regenerated from explants of chimera materials
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