KARYOTYPIC CHANGES AND SELECTION PRESSURE IN <i>HAPLOPAPPUS GRACILIS</i> SUSPENSION CULTURES

Abstract

Two cell lines with 6 and 16 chromosomes were obtained from a predominantly diploid (4-chromosome line) suspension culture of Haplopappus gracilis (Nutt.) Gray. Selection was found to be 'conservative' in the 4- and the 6-chromosome line, while it was 'progressive' in the 16-chromosome line. Mitotic abnormalities and chromosomal aberrations were most frequent in the 16-chromosome line and least frequent in the 4-chromosome line.When grown in mixtures the frequency of one line increased while the other line or lines were rapidly eliminated. The 4-chromosome line showed the highest fitness. It was concluded that the 6- and/or the 16-chromosome lines were eliminated from mixtures due to slower growth rates.