CHROMOSOMAL VARIABILITY AND GROWTH-RATE IN CELL-SUSPENSION CULTURES OF STEVIA-REBAUDIANA (BERT) BERTONI

Several cell lines were obtained from a predominantly diploid (2n = 22) cell suspension culture of Stevia rebaudiana by colchicine treatment (10(-3)M/72 h), filtration in 100-500 mu m sieves and plating followed by visual selection. Colchicine treatment resulted in a highly polyploid line, but with a tendency for reversion to a chromosome distribution profile (CDP) similar to the initial culture, but with a higher growth rate. Selection by filtration showed a relationship between cell aggregate size and the CDP, cells of higher ploidy having a tendency to form smaller aggregates. After plating, calli with several characteristics (shape, colour, degree of friability) were selected, and gave rise to cell lines with different CDPs; these cell lines were used to initiate predominantly diploid, tetraploid or aneuploid cell suspensions that showed characteristic growth rates and aggregate sizes.