Resistance of winter cereals to various winter stress factors - inter- and intraspecific variation and the role of cold acclimation

This work was undertaken to study the inter and intraspecies variation in winterhardiness of overwintering cereal species and to find out the reasons for this variation. The studied 24 winter wheat (Triticum aestivum L.), 13 rye (Secale cereale L.), 5 triticale (X Triticosecale Wittmack) and 11 barley (Hordeum vulgäre L.) cultivars differed highly significantly from each other in winter survival ability determined in field trials during 1989-1992 at six locations in Finland and at altogether 17 locations in all the Nordic countries. The Field Survival Indexes of cultivars were determined, too. Rye was the most winter hardy species followed by winter wheat, triticale and barley. Since field trials often fail to screen the resistance of plants to specific winter stress factors, such as frost or snow mould, laboratory tests were used to study these factors. On the basis of the results it could be concluded that, during cold acclimation, sugars and proline are accumulated, and the fatty acid composition of the plasma membrane lipid fractions is changed. Cold acclimation enhances frost resistance and general winterhardiness of overwintering cereals, but part of the snow mould (Microdochium nivale (Fries) Samuels & Hallet) resistance may be induced without low temperature treatment. Thus, different resistance mechanisms may be controlling frost and snow mould resistance. The results of this study suggest that general winterhardiness of overwintering species could be enhanced by screening separately resistance mechanisms of plants to various specific winter stress factors and combining these into new cultivars.