Environmental and genotypic control of time to flowering in canola and Indian mustard

The timing of flowering in canola (Brassica napus) is an important determinant of adaptation to its environment. Cultivars of canola varying in maturity are grown over a wide range of photoperiod and temperature conditions in Australia. A quantitative understanding of the genotypic and environmental control of time to flowering can be used to improve breeding programs and crop management strategies. Controlled environment and field studies were used to determine the responses of 21 cultivars of canola and breeding lines of Indian mustard to vernalisation, temperature, and photoperiod. The number of days to flowering in all genotypes was reduced in response to vernalisation and long days, due to a reduced duration between sowing and buds visible. The vernalisation response was saturated with c. 25 days at 3degrees C. Base and optimum temperatures for development were confirmed at 0 and 20degrees C, respectively. The photoperiod response occurred between 10.8 and 16.3 h, and plants responded to photoperiod from emergence. A simulation model incorporating these effects was developed, which predicted days to flowering with a mean deviation of c. 5 days. Later flowering genotypes had model parameters that indicated greater responses to vernalisation and photoperiod than early-flowering genotypes.