Breeding aspects of low temperature tolerance in wheat

Wheat resistance to low temperatures is complex in nature and dependant on variety as well as on interaction with the environment. In unfavorable conditions for hardening, even varieties resistant to cold may exhibit higher susceptibility to low temperatures. Over a two-year period (2003-04), tests were conducted in cold chamber at-15 C lasting 24, 36, 48 and 60 hours. The 23 wheat varieties analyzed were divided into four groups according to year of release. In the first group, which was mostly made up of foreign introductions, the average plant survival rate across treatments was 87%. The different origins of the varieties from this group were a significant factor behind the differences in their resistance levels. The second group, comprised of the first domestic varieties, had an average plant survival rate of 89%, while the third, containing the dominant varieties from the 1980s, had a plant survival rate of 88.4% on average. In the fourth group, consisting mostly of varieties that are currently commercially grown in the country, the average plant survival rate was 86.6%. Thanks to high temperatures present during the process of hardening, there was greater plant damage and percent winterkill in the second year than in the first. The resistance of the varieties to low temperatures has been maintained at a level enabling successful and stable production under the cold temperature stress conditions of southeastern Europe.