Hybridisation between Brassica napus L. and Raphanus raphanistrum L. underagronomic field conditions

The frequency of hybridisation between Brassica napus L. and Raphanus rapha nistrum L. under agronomic conditions was assessed in field experiments, wh ere R. raphanistrum were randomly planted at two different densities into l arge plots of B. napus. An acetolacate synthase (ALS)-inhibiting herbicide- resistant trait was used to detect potential hybrid individuals. No hybrids were detected amongst 25,000 seedlings grown from seed collected from R. r aphanistrum plants. Two hybrids were obtained from more than 52-million B. napus seedlings. Both hybrids were characterised as amphidiploids (AACCRrRr , 2n = 56) and were fertile. The frequency of hybridisation into B. napus i n this experiment using male-fertile B. napus was 4 x 10(-8).