Occurrence and cytogenetic development of unreduced pollen in Vitis

Percentages of unreduced pollen (>40 µm for tetraploids, >30 µm for diploids) produced in 13 tetraploid V. labruscana x V. vinifera hybrid cultivars were higher than those in 11 of 14 diploid cvs and species (0.18-1.27 and 0.06-0.37 %, respectively). The production of 2x pollen was positively correlated to dyad formation during microsporogenesis, the frequency of dyad formation varied among cvs and flowers for 4x genotypes. Cytogenetic studies showed that the predominant mechanism of unreduced pollen production was first division restitution (FDR) accompanied by a lower proportion of co-orientation of second division spindles. The prospects of utilization are briefly discussed