Freezing and Ice Encasement Tolerance of Arctic Timothy Varieties after Seed Multiplication for One, Two or Three Generations at Lower Latitudes

ABSTRACT Seed multiplication of perennial grasses outside their area of adaptation is common practice globally. This also applies to timothy ( Phleum pratense L.), the most important forage grass in Arctic Norway (67°–71° N). Early research suggests little risk for loss of winter hardiness if seed multiplication of Arctic timothy is limited to one or two generations in the south, but recent experiences by North Norwegian farmers suggest otherwise. A study was conducted in which original seed of two northerly adapted timothy varieties ‘Engmo’ (an old landrace originating at 69° N) and ‘Noreng’ (a synthetic variety consisting of 10 clones of ‘Engmo’ and four clones of the South‐Norwegian variety ‘Grindstad’) was multiplied for one, two or three generations at 70° N, 64° N and 58° N. Plants raised from the different generations at each site were subjected to freezing tests to determine LT 50 and ice encasement (IE) tests to determine LD 50 , both tests followed by the weighing of regrowth of surviving plants. On average for generations and compared with the original seed, we found no changes in freezing tolerance or IE tolerance after seed production at 70° N, but significant losses in freezing tolerance of both varieties after seed production at 64° N and in particular at 58° N. The fact that major shifts occurred already in the first generation and were later, at least to some extent, reversible and influenced by the winter before each seed harvest raises the possibility that epigenetic memory of environmental conditions was transferred to the seed progeny in addition to the classical genetic effects.