Transmission and Significance of B Chromosomes in Anthurium Warocqueanum J. Moore

Abstract

Somatic and meiotic chromosomes of Anthurium varocqueanum J. Moore and its selfed offspring were analyzed. The parent showed 2n=30 + 3B in both somatic cells and pollen mother cells. In somatic cell division B chromosomes behaved regularly, whereas their meiotic activities were found to be variable. Three configurations of 3 B chromosomes were observed at metaphase I of parent meiosis: one trivalent, one bivalent and one univalent, and three univalents. At anaphase I univalent B chromosomes tended to lag and eventually form micronuclei. The number of B chromosomes in offspring ranged from 0 to 6, indicating their transmission from both male and female gametes. The offspring with 2 B chromosomes appeared in greatest frequency. It was hypothesized that both male and female gametes frequently contained one B chromosome through the normal distribution of the bivalent B at meiosis and the elimination of the univalent B due to lagging. Investigation on pollen mother cells of offspring also revealed irregular behavior of B chromosomes. When two or more B chromosomes were present, 2 Bs were often associated together at early meiotic stages and had normal disjunction at anaphase I. In contrast, univalent B chromosomes showed variable movements during anaphase I; moving toward either poles, lagging, or two sister chromatids separating to opposite poles. With the higher number of B chromosomes, normal A chromosome bivalent formation seemed to be reduced. No distinct phenotypic effects of B chromosomes in Anthurium warocqueanum were observed.