Identifying Hybrids

1. Flow Cytometry

Flow cytometry is used to identify triploid plants (B. rapa x B. napus hybrids), and is carried out by Plant Cytometry Services (Schijndel, The Netherlands).

Nuclei are isolated from fresh leaf samples, including known controls, and stained with a flourescence dye (DAPI). The cell suspension is then passed through a flow cytometer which measures the amount of flourescence produced from individual cells, producing traces such as those to the left. The height of the peak indicates the number of cells measured, and the distance along the bottom (X) axis shows the degree of flourescence; the greater this is, the more DNA is contained by the cell. The top plot is that of B. rapa (diploid), the second is B. napus (tetraploid) and the third is that of a hybrid of the two (triploid).

2. SSR-PCR

Simple Sequence Repeat Polymerase Chain Reaction (SSR-PCR) was used to establish the hybrid status of any triploid plants identified by flow cytometry.