Screening Fast Emergence and Cold Tolerant Canola Cultivars for Semi-Arid Regions of the Northern Great Plains.

In Montana and other semiarid region of the northern Great Plains, dryland canola production is often constrained by hot, dry summer and short growing season. Heat stress during flowering can cause flower abortion and greatly reduce seed yields. Early seeding can alter the timing of plant growth and development and avoid the negative impacts of heat and drought stress at critical growth stages. Previous studies conducted at Moccasin and Conrad, Montana showed that late-March-seeded canola yielded 0-5% greater than mid-April seeding and delaying seeding from mid-April to mid-May resulted in 43 to 63% yield reduction. The objective of this study was to screen suitable cultivars for early spring seeding. The suitable cultivars must have quick germination, emergence, and establishment at low temperatures; also the seedlings must be tolerant to early spring freezing and thawing events. Field and growth chamber studies were conducted at the Central Agricultural Research Center of Montana State University at Moccasin, MT to determine the minimum temperature or base temperature (Tb) for germination and heat units or growing degree days to 50% emergence (GDD50). The Tb for germination was found to be less than 4^oC and the growth degree days for 50% emergence (GDD50) were 42-81. Different cultivars exhibited different heat unit requirements for emergence both in the growth chamber and field. Field studies also showed that canola biomass and grain yields were negatively correlated to the GDD50.