Separation of tetraploid and diploid plants from chimeras in in vitro cultures of purple coneflower (echinacea purpurea l)

Abstract

Doubling the chromosome number of diploid and haploid Echinacea purpurea plants have high applica ble 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% tet raploid 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 cul ture 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. Re sults of the experiments indicate that in vitro culture method could provide a useful way to separate chi meras 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