Ploidy dimorphism and reproductive biology in Stenodrepanum bergii (Leguminosae), a rare South American endemism

CAPONIO, I.; ANTON, A.M.; FORTUNATO, R. H.; NORRMANN, G.A.

GENOME

NATL RESEARCH COUNCIL CANADA-N R C RESEARCH PRESS

Año: 2012 vol. 55 p. 1 - 7

0831-2796

This is the first report on chromosome numbers and the reproductive behaviour in Stenodrepanum Harms, a rare endemic and monotypic Legume genus from the arid and salty areas of Central-Western Argentina. We surveyed populations from two salty areas (“salinas”) and found mostly triploid (2n = 3x = 36) and only two diploid (2n = 2x = 24) plants.  Meiosis in diploids is regular, with bivalent pairing and uniform and well-coloured pollen. In contrast, meiosis in triploids is characterized by high trivalent pairing, with irregularly  shaped pollen and variation in cyotoplasm content and tinction, which is in agreement with an unbalanced segregation occurring in anaphases I and II. However, different triploid plants/individuals/s showed various degrees of pollen fertility which may be attributed to particular genotypes. Research on reproductive biology events indicates sexual cross-pollinated reproduction enhanced by protogyny in both cytotypes.  All plants produced seeds, but seedlings were only recovered from diploid plants pollinated with triploids and even those eventually perished.  Chromosome counts in these seedlings revealed aneuploid chromosome numbers due to the combination of unbalanced gametes.