POLYPLOIDY IN THE VICIA SATIVA AGGREGATE

Polyploidy is rare in the genus Vicia and is absent in the Vicia sativa aggregate which is composed of types with 2n= 10, 2n= 12 and 2n= 14. Spontaneous amphidiploids were selected among 2n= 10 × 2n= 14 and 2n= 12 × 2n= 14 hybrid derivatives. Chromosome association at meiosis was mainly as bivalents in these amphidiploids; occasionally they were heteromorphic. The spontaneous amphidiploids were inferior to their diploid parental lines in growth rate, vigour and seed set over three generations. The behaviour of the spontaneous amphidiploids was compared with artificially induced autotetraploids. Meiosis in the autotetraploids was characterized by a lower number of associations per chromosome and small number of multivalents. The growth rate of the autotetraploids was retarded and seed set was lower in comparison with the diploid lines. The diploid and the autotetraploid lines could be easily separated from one another by the shape of their pollen grains; elliptical in the diploid plants and tetrahedral in the autotetraploids. No such modification of the pollen grains was observed in amphidiploids. The potential for polyploidy in Vicia sativa and possible reasons for its absence in that aggregate are discussed.