MEIOTIC RESTITUTION MECHANISMS AND 2N POLLEN FORMATION IN A SOLANUM-TUBEROSUM DIHAPLOID AND IN DIHAPLOID X WILD-SPECIES HYBRIDS

A Solanum tuberosum dihaploid that proved to be a 2n pollen producer, exhibited two types of meiotic abnormality involved in 2n pollen forma tion: premature cytokinesis at prophase II and parallel/tripolar spind les in meiosis II. For this reason such a dihaploid was preferentially used as a seed parent in crosses with the diploid species S. tarijens e, S. sanctae-rosae, and S. phureja. Diploid interspecific hybrids wer e evaluated for male fertility, for 2n pollen production and stability over three years and for meiotic nuclear restitution mechanisms. Poll en stainability ranged from 6 to 85% and 2n pollen from 5 to 35% among hybrids. The meiotic mechanism generating 2n pollen was that of spind le abnormality in meiosis II and consequent dyad/triad formation. High correlation was found between fused/parallel spindles and dyads.