Flow cytometric detection of unreduced pollen in Begonia

Unreduced gametes, formed due to a disruption in meiosis, are considered to play an important role in the formation of polyploids in nature. A screening method for the detection of unreduced gametes in ornamentals is however needed. Begonia was used as a model plant for the detection of unreduced pollen. Chemical, enzymatic, mechanical and osmotic assays have been used for the isolation of nuclei from Begonia pollen. The relative DNA content of pollen nuclei was measured using flow cytometry. Two methods, on germinated and non-germinated pollen, were successfully applied. Flow cytometric analysis showed two peaks in pollen, associated with the vegetative (1C) and generative (2C) nuclei of normal (reduced) pollen. Two of seven tested Begonia genotypes showed a peak at the 4C level, associated with the presence of unreduced gametes. Formation of unreduced gametes was associated with abnormalities in pollen shape or pollen size.