Chromosomal behavior in rhoeo discolor against colchicine treatment

Abstract

Rhoeo discolor (2n=12) exhibit a complete translocation heterozygote in which a ring of 12 chromosomes is often observed from diakinesis through metaphase-1. This was used to study the effect of colchicine on chromosome pairing during meiosis. Pachytene pairing appeared unaffected, but only 9.80% of the PMCs formed a ring of 12 chromosomes at metaphase-I of meiosis. While 16.60% of cells had a complete chain of 12, 66.20% had chain configurations of varying (211) number of chromosomes and 7.10% had complete univalence. Adjacent orientation was found in the majority of cells with chain complexes of 2-11 choromosomes. The result was highly disturbed post metaphase-1 stages. 76% of anaphase-I and 64% of telophase-1 stages were abnormal. Only 42% pollen grains were fertile and 26% pollen grains showed abnormal chromosome number at pollen mitosis. It is concluded that the presence of aberrant cells at metaphase-I is either due to colchicine induced ineffectiveness of pairing at the very small pairing region or to the failure of chiasma formation. ©2012 The Japan Mendel Society.