200 – II.3. BRASSICA CROPS (BRASSICA SPP.)
Figure 3.36. Outcrossing percentages as affected by distance from the pollen source
Note: (MS) indicates male sterile bait plants used.
Source: Modified from Andersson and de Vicente (2010).
Where fields are large (>60 hectares) and/or production regions are extensive,
as in Australia, Canada and India, wind is considered to be the primary pollen vector
since bee populations cannot service the vast number of exposed flowers. However, in the
United Kingdom and other parts of Europe where field size is small and bees and pollen
beetles are abundant, insects play an important role in pollen dispersal, especially over
long distances (Ramsay, Thompson and Squire, 2003; Ramsay et al., 1999;
Thompson et al., 1999). Pollen distribution by insect can vary greatly depending on the
production region, the environment and the experimental design (Barber, 1999;
Thompson et al., 1999; Ramsay, Thompson and Squire, 2003). Honey bees visiting a new
field are covered with pollen from that field after visiting about four flowers, thus
