Meiosis in Aneuploids of Tetraploid Lathyrus Odoratus and L. Pratensis

Abstract

Meiosis was studied in one hypoploid (trisomic, 2n = 4x - 1 = 27) of an induced tetraploid (2n = 28) of Lathyrus odoratus and two hyperploids (single pentasomic, 2n = 4x + 1 = 29 and double pentasomic, 2n = 4x + 1 + 1 = 30, respectively) of an induced tetraploid of L. pratensis. Multivalent frequencies in the aneuploids were high, but the numbers of chiasmata were not sufficient to maintain all pairing configurations till metaphase I. Interstitial chbdsmata were relatively frequent. Chiasma frequencies were considerably reduced in all three aneuploids, compared with the eutetraploids. The two pentasomes (sets of five homologous chromosomes) of the double pentasomic were both present as a quinquivalent more frequently than expected when they would behave independently. The single pentasomic and the trisomic did not deviate much from expected, although, like in the eutetraploids, the multivalent frequencies were considerably higher than corresponds with the assumption that pairing initiation is restricted to the chromosome ends. The conclusion is that aneuploids of Lathyrus at the tetraploid level tend to behave similar to euploids, except that the chiasma frequency is considerably reduced. When maintained in the population their progeny will contain even more aneuploids than the euploids, not only because the aneuploidy will be perpetuated, but also because of lower chiasma frequencies leading to univalent formation. J. Sybenga, Fazantenlaan 4, NL-4351 RV Veere, The Netherlands