Varietal Differences in the Overwintering Ability of Onion Plants Growing in Snow Associated with Soluble Carbohydrate Accumulation

Abstract

In this study, we investigated the relationship between onion growth during snow cover and varietal differences in soluble carbohydrate accumulation and survival rates after snow melting. The survival rate after melting differed among varieties and was highest in ‘Tarzan’ suggesting that overwintering ability under snow differs according to the variety. No relationship was found between the survival rate after snow melting and size of the plant from the beginning of snow cover to after melting. At the beginning of snow cover, soluble carbohydrate accumulation of the leaf sheath was about twice that of the leaf blade. The leaf sheath accumulated a larger amount of polymerized fructan compared with the leaf blade. The soluble carbohydrate accumulation decreased from the beginning of snow cover until melting. The kestose content (1-kestose plus neokestose) of the leaf sheath after melting was also determined; here too it was highest in ‘Tarzan’. The findings suggest that fructans—especially residual fructans in the leaf sheath—are important for survival and growth following snow melting. Consistent with this, the consumption of soluble carbohydrates by onions growing in snow was low, and it is considered that this affects the amount of residual fructan after melting. The results suggest that the metabolism of soluble carbohydrates during snow cover is related to the overwintering ability of onions under snow. ‘Tarzan’, which has little soluble carbohydrate content during snow cover and retains fructan after snow melting, and has a high overwintering ability, suggesting that it is a suitable variety for autumn-sowing cultivation in snowy areas.