FLAX (LINUM-USITATISSIMUM L) RESPONSES TO CHILLING AND HEAT-STRESS ONFLOWERING AND SEED YIELD

The effect of a 5 degrees C chilling treatment at the seedling stage o n days to flower, yield and oil quality and quantity was determined fo r seven cultivars of flax (Linum usitatissimum L.). Three days of chil ling delayed flowering in Dufferin, McGregor and NorLin, whereas 5 d o f chilling delayed flowering in all cultivars except Andro and Noralta . Seven days of chilling reduced the seed yield of only McGregor, Norl in, NorMan and Vimy. The effect of a 40 degrees C heat stress at the f lowering stage on yield and oil composition was determined for the sam e seven cultivars. A heat stress of 40 degrees C for 3 d reduced the s eed yield of NorMan, whereas, a 5 d stress reduced the seed yield of a ll cultivars except McGregor and Noralta. The composition of the oil w as not affected by the heat stress. These results suggest genetic vari ability exists among flax cultivars for tolerance to chilling and heat stresses. Controlled tests can be used to select superior stress tole rant genotypes.