MEIOTIC CHROMOSOME BEHAVIOR IN INDUCED AUTOTETRAPLOIDS AND AMPHIDIPLOIDS IN THE <i>LOTUS CORNICULATUS</i> GROUP

Abstract

A comparative meiotic study was conducted on 12 induced Lotus autotetraploids (2n = 4x = 24; L. alpinus, L. japonicus, L. filicaulis, L. schoelleri, L. krylovii, L. tenuis and L. corniculatus var. minor), and 22 amphidiploids (2n = 4x = 24) obtained by doubling the chromosome number of 12 diploid interspecific hybrids. Meiocytes of the autoretraploids were characterized by a rather high frequency of bivalents (average 8.79 per cell) and a low occurrence of quadrivalents (average 0.77 per cell). In many of the amphidiploids there was a relatively high frequency of bivalents (mean 9.92 per cell) and a low number of multivalents (mean 0.39 per cell) providing evidence for the structural differentiation of the chromosomes and preferential pairing. Homology of the chromosomes of the parental species was indicated by the presence of trivalents and quadrivalents, and the occurrence of inversion bridges with accompanying fragments in the amphidiploids. It appears that the chromosomes of L. japonicus and L. alpinus have considerable homology since the amphidiploid (L. japonicus × L. alpinus) 2 exhibited a high frequency of quadrivalents in comparison with the number of quadrivalents observed in L. japonicus (4x) and L. alpinus (4x), A comparison of a) the pollen stainability and b) the frequencies of multivalent configurations in the autoretraploids and the amphidiploids indicated that both multiple gene substitution and cryptic structural changes of the chromosomes are important in differentiating the diploid species.