Ploidy doubling by in vitro culture of excised protocorms or protocorm-like bodies in <Emphasis Type="Italic">Phalaenopsis</Emphasis> species |
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Authors: | Wen Huei Chen Ching Yan Tang Yu Lin Kao |
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Institution: | (1) Department of Life Sciences, National University of Kaohsiung, No. 700, Kaohsiung University Road, Nan-Tze District, Kaohsiung, 811, Taiwan, ROC |
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Abstract: | Endopolyploidy was observed in the protocorms of diploid Phalaenopsis aphrodite subsp. formosana with ploidy doubling achieved by in vitro regeneration of excised protocorms, or protocorm-like bodies (PLBs). Thirty-four
per cent of the PLBs regenerated from the first cycle of sectioned protocorms were found to be polyploids with ploidy doubled
once or twice as determined by flow-cytometry. The frequency of ploidy doubling increased as the sectioning cycles increased
and was highest in diploid followed by the triploid and tetraploid. Regeneration of the endopolyploid cells in the tissue
of the protocorms or PLBs is proposed as the source of the development of ploidy doubled plantlets. The frequency of ploidy
doubling was similar in seven other Phalaenopsis species, although the rate of increase within cycles was genotype specific. In two species, a comparison of five parameters
between 5-month-old diploid and tetraploid potted plants showed only the stomata density differed significantly. The flowers
of the tetraploid plant were larger and heavier than those of the diploids. This ploidy doubling method is a simple and effective
means to produce large number of polyploid Phalaenopsis species plants as well as their hybrids. The method will be beneficial to orchid breeding programs especially for the interspecific
hybridization between varieties having different chromosome sizes and ploidy levels. |
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Keywords: | Endopolyploidy Phalaenopsis orchids Polyploidy Ploidy doubling Protocorm-like bodies |
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