Microsporogenesis in three tetraploid somatic hybrids of potato and their di(ha)ploid fusion partners.

The microsporogenesis of three somatic hybrids of potato, i.e. one tetraploid Solanum tuberosum (+) S. phureja, one tetraploid and one hypertetraploid S. tuberosum (+) desynaptic mutant, has been examined and compared with the microsporogenesis of the di(ha) ploid fusion partners. The somatic hybrids had a first meiotic division with uni-, bi-, and multivalents like that of tetraploid potatoes, illustrating introgression and dominance over desynapsis. Abnormal spindle orientations at second meiotic division, sporad types with reduced and unreduced cells and viable pollen occurred at various frequencies. Pollen fertility could not be predicted on the basis of pollen fertility of the fusion partners. Pollen sterility was partially due to abnormal chromosome numbers. Only the tetraploid S. tuberosum (+) desynaptic mutant produced normal amounts of viable seeds.