CHROMOSOME ASSOCIATIONS AT PACHYTENE AND METAPHASE IN MEDICAGO SATIVA

Abstract

Chromosome associations were analyzed at pachytene and metaphase I from six plants of Medicago sativa L. (2n = 4x = 32). Quadrivalent frequency at pachytene ranged from 0.89 to 2.93. These values are considerably below theoretical expectations for an autotetraploid. The chromosome associations at metaphase I did not entirely reflect differences in quadrivalent frequency at pachytene, although there was a general tendency for plants with higher quadrivalent frequencies at pachytene to have a higher trivalent and univalent frequency at metaphase I. However, there were obvious differences in the amount and kind of pachytene quadrivalent dissociation that occurred, which are probably a result of small differences in chiasma frequency and distribution.