Effects of temperature and photoperiod on frost resistance of white clover (Trifolium repens) ecotypes.

Effects of photoperiod and temperature on frost resistance of seedling populations and clones of white clover (Trifolium repens L.) originating from various latitudes (58°48'-69°54'N) and altitudes (up to 1 100 m above sea level) were studied in a phytotron. Low-temperature-induced cold acclimation in all populations was significantly stimulated by short photoperiod and low temperature. The highest levels of host resistance were found in the northernmost seedling populations and in clones from northern coastal locations. [ABSTRACT FROM AUTHOR]