High Degree of Genetic Variation of Winter Hardiness in a Panel of Beta vulgaris L.

Growing sugar beet (Beta vulgaris L. subsp. vulgaris [sugar beet cultivar group]) as a winter crop requires the development of a winter sugar beet with controlled bolting and sufficient winter hardiness. To evaluate the genetic variation for winter hardiness in B. vulgaris L., we determined the survival rate (SR) in a panel of 396 accessions tested in eight overwintering field trials in Germany and Belarus. The panel included the cultivar groups sugar beet, fodder beet, garden beet, and leaf beet, as well as the wild beet B. vulgaris subsp. maritima (L.) Arcang. (BVM). Across all environments the effects of accession, environment, and accession x environment interaction were highly significant. Despite the complexity of the trait, the heritability for SR was estimated as h(2) = 0.81, reflecting a large genetic variation in the panel. Environmental SRs ranged from 0.7 to 86.3% with a grand mean of 28.4%+ In all environments at least one accession completely died while the maximum SR ranged from 39.9 to 100%+ On average, sugar beet accessions performed best while accessions with the highest SR were among BVMs and leaf beets. The largest variation for SR was found in BVMs, followed by the leaf beets, whereas sugar beets showed the smallest variation. Our results suggest that winter hardiness in sugar beet is sufficient to survive mild winters but needs to be improved for continental climates with colder winters. Whether the limited variation in sugar beet is sufficient for this has to be further investigated.