Meiotic Analysis of Astragalus cicer L. II. Polyhaploids

Meiotic behavior of polyhaploids (2n = 4x = 32) of Astragalus cicer was strongly diploid-like. Bivalent frequencies exceeded 95% in the four plants studied, and a majority of meiotic configurations comprised exclusively bivalents. Meiosis was highly regular in polyhaploids 37B and 38B, but plants C17 and 353B produced a greater diversity of configurations reflecting their markedly higher frequencies of univalents. Optimization analysis revealed close correspondence to the 2: 2 pattern of chromosome pairing expected of amphidiploids, and estimates of relative genomic affinity indicated that chromosome pairing was almost exclusively intragenomic. Polyhaploids of A. cicer evidently comprised two pairs of distinct genomes (AABB) that paired preferentially (homologously). Natural octaploids of A. cicer are therefore autoallooctaploids with genomic formula AAAABBBB. Diploid-like meiotic behavior of octaploid A. cicer, despite the autotetraploid nature of constituent genomes, indicated that multivalent formation was suppressed and bivalent frequencies thereby enhanced by a bivalentizing system.