Discrepancy between spindle anomalies and 2n pollen production in Solanum interspecific hybrids

The cytological basis of 2n pollen production was studied in a diploid Solanum progeny coming from a cross between a S. tuberosum-S. chacoense hybrid which does not produce 2n pollen (T710) and a S. phureja-S. tuberosum hybrid (W5295.7) which does. Both parental clones showed anomalous orientation of spindles at Metaphase II of microsporogenesis, but only clone W5295.7 produced dyads. All plants of the progeny T710 x W5295.7 showed anomalous spindles at Metaphase II, but only 60% of them produced 2n pollen, thus evidencing a discrepancy between spindle anomalies and dyad/2n pollen production. This may suggest that both parallel and fused spindles are a necessary but insufficient condition for 2n pollen production, and that some other mechanisms expected to be more highly correlated with them may be involved in 2n pollen production in this population.