Production of triploid Sandersonia aurantiaca plants

Triploid plants of Sandersonia aurantiaca were produced by crossing diploid and tetraploid forms of S. aurantiaca. Enlarged ovules were transferred to in vitro culture 14–30 days after pollination. The triploid nature of the embryo derived plants was determined by flow cytometry and chromosome counts both of which showed that the triploid plants had features that were midway between those of the two parents. The mean nuclear DNA contents of 2C nuclei from diploid, triploid and tetraploid forms of S. aurantiaca were 6.86pg, 10.04pg and 13.55pg, respectively. The nuclear DNA content of 1C nuclei of sperm cells from pollen grains was 2.94pg. Mitotic chromosome counts from the three plants gave 2n = 24, 36 and 48 chromosomes for the diploid, triploid and tetraploid forms, respectively. Meiotic chromosome counts for the diploid and tetraploid plants were n = 12 and n = 24, respectively. The triploid showed mainly bivalents, but lagging chromosomes led to micronuclei and infertility in gametes. The morphological features of the various plants corroborated other evidence indicating that the triploid plants were the result of a cross between diploid and tetraploid plants