Cold acclimation threshold induction temperatures in cereals

To acquire a competitive advantage and ensure survival when exposed to low-temperature extremes, cool season plants must be programmed to respond to temperatures favorable for growth and environmental cues that signal seasonal changes. This project was initiated to determine (i) the cold acclimation threshold induction temperatures (ITs) in wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), and rye (Secale cereale L.) and (ii) their relationship to plant freezing tolerance at full acclimation. A wide range of genotypic specific IT and initial rapid acclimation responses that were inversely related to decreases in temperatures below the threshold was observed both within and among species, indicating that cereals monitor temperature with a high level of precision. Hardy wheat cultivars had a 5.7 degrees C warmer activation temperature than tender genotypes when the vernalization gene was neutralized in near-isogenic lines, and a 12 degrees C difference in IT of hardy rye compared with tender barley cultivars emphasized the high cold adaptation potential of rye. This early response to decreasing temperatures means that hardy rye had a longer time to prepare for the extremes of winter and was in a better position to cope with unexpected frosts during the growing season. Differences in IT were closely related to the differences in freezing tolerance at full acclimation. However, a longer vegetative stage also meant that winter habit genotypes were more responsive to extended periods at acclimation temperatures in the threshold range.