Meiosis in Autotetraploid Lolium perenne in Relation to Chromosomal Behavior in Autopolyploids

Abstract

Meiotic behavior was studied in pairs of diploid and tetraploid clones obtained by vegetative propagation from chimeral plants resulting from treatment of germinating seeds with solns. of colchicine. As compared with the diploid clones, there was in the tetraploids a delay of chromosome contraction relative to the onset of me.taphase I and in 2 clones absence of orderly orientation on the equatorial plate prior to initiation of anaphase I. In some pairs the chiasma frequency of the tetraploid clone was lower than in the diploid; in other pairs the differences were not significant. There were 3 major types of meiotic irregularity in the tetraploid clones (a) the members of the quadrivalents frequently disjoined unequally at anaphase I; (b) lagging and dividing univalents at anaphase I resulted in some cases from incomplete disjunction of quadrivalents; and (c) there was a high incidence of univalents at metaphase I that tended to lag and divide equationally at anaphase I and to be left in the cytoplasm at telophases I and II. Variations in meiotic behavior among the tetraploid clones were not significantly correlated with variations among the diploid clones. The frequencies of anaphase I sporocytes with dicentric bridges and acentric fragments in the tetraploid clones did not differ greatly from the frequencies calculated[long dash]assuming random pairing of inverted and normal chromosomes[long dash]from those obtained in the comparable diploid clones.