2n gametes in Solanum tuberosum dihaploids

Pollen stainability over two years and microsporogenesis were investigated in seven dihaploids extracted hom Solanum tuberosum tetraploids (AVRDC-1287 .19, Conchita, Merrimack and W231). Two dihaploids proved to be male-steril e and male gamete abortion is likely to be post-meiotic because a regular m eiosis occurred. The other dihaploids proved to be partially male-fertile a nd 2n pollen producers, as well. Almost all clones showed predominantly the formation of parallel spindles. Correlations estimated between the observe d abnormalities in spindle orientation and the meiotic products evidenced a high correlation between parallel/fused spindles and dyads. The dihaploids were also used as parents in crosses with tetraploids, One berry with 44 s eeds was obtained from dihaploid AVI 24 used as pollen parent in 4x x 2x cr osses. After 2x x 4x crosses, three dihaploids including the two male-steri le were found to be 2n egg producers. The formation of 2n gametes in S. tuberosum dihaploids is discussed in rela tion to a direct use of dihaploids in sexual polyploidization schemes to co mbine useful traits in a superior genotype at 4x level.