VERNALIZATION RESPONSE IN SPRING OILSEED RAPE (BRASSICA-NAPUS L) CULTIVARS

Early maturity is a major objective of oilseed rape (Brassica napus L. ) breeding programs in western Canada. Maturity of crops is influenced by time of initiation and flowering. The presence of a vernalization requirement affects plant development by delaying floral initiation un til the cold requirement of the plant has been satisfied. Five spring oilseed rape cultivars were screened for their response to vernalizati on. Vernalization treatments consisted of exposure of germinated seeds to 0-42 d at 4 degrees C. Plants were assessed under a 20-h photoperi od. In general, there was a cumulative response to vernalization, with a decrease in days to each developmental stage as exposure to 4 degre es C was increased. Vernalization treatment of 6 d at 4 degrees C was sufficient to decrease both the days to first flower and the final lea f number. The characterization of vernalization response is of interes t because variation in flowering time in response to year-to-year vari ations in the environment could result.