Bilateral sexual tetraploidization in red clover

Twenty-four diploid red clover (Trifolium pratense L.) plants, from the cultivars 'Arlington', 'Florex', and 'Redman', and C760, a Wisconsin synthetic, were tested for 2n egg production by crossing them with tetraploid plants. Four plants were identified and selected as 2n egg producers. These plants were then crossed with a known producer of 2n pollen in an attempt to obtain tetraploid plants through bilateral sexual polyploidization. Thirteen percent of the seed obtained in one of the 2x–2x crosses were tetraploid. The female plant produced an estimated 0.14 2n eggs per 1000 flowers in the cross. In a second experiment, bilateral sexual polyploidization was attempted, using 14 plants which had not been previously tested for 2n egg production. Two of these plants produced one and two tetraploids each, representing 2n egg frequencies of 3.33 and 5.00 2n eggs per 1000 flowers, respectively. It seems likely that it will be possible to use bilateral sexual polyploidization to tetraploidize red clover germplasm in the future.Key words: tetraploid red clover, Trifolium pratense. 2n gametes.