Abstract. The seed set, in two red clover cultivars (Select-1, diploid and Apollo-tetra, tetraploid) was analysed in an experiment in which the two cultivars were planted in merging plots. An obvious decrease of no. of seeds/inflorescence was noticed in the diploid cultivar, especially in plants situated near by the tetraploid cultivar. On the contrary, in tetraploid red clover plants there has been noted a significant increase of seed set, this increase being the greatest when the proximity to the diploid cultivars was very tight. It is concluded that in experimental fields with tetraploid clover, if a diploid cultivar is used as control, the tetraploid variants could be easily underestimated from seed production point of view due to the fact that the diploid control, with its "overproduction" of pollen, becomes the main pollinator of tetraploid variants. It is also recommended that, in seed production plots of red clover cultivars with different ploidy levels, a strip of 7-8 cm should be eliminated before harvest to avoid both mechanical and biological contamination.

Key words: red clover, diploid, tetraploid, conservative breeding

Presentation: oral