Study of faba bean (Vicia faba L.) winter-hardiness and development of screening methods

In cool-temperate regions, faba bean (Vicia faba L.) is mainly grown as a spring crop despite the higher yield potential of the winter type, because of the insufficient winter-hardiness of the present winter genotypes. The objective of this study was to assess winter-hardiness and frost tolerance, to quantify the hardening effect on physiological traits, and to identify auxiliary traits for winter-hardiness. To do so, 31 representative entries were tested in controlled frost tests for frost tolerance and in 12 European environments for winter-hardiness. Total fatty acid composition, proline content, and electrolyte leakage of leaves were analysed. Across all environments, five European winter genotypes were identified with superior winter-hardiness. Controlled frost tests indicated that frost tolerance is a significant, but not an exhaustive component of winter-hardiness (0.021 < |r| < 0.737**). These tests revealed the high frost tolerance of several poorly winter-hardy experimental lines and the limited frost tolerance of well-known winter types. Fatty acid changes due to hardening, proline content, and electrolyte leakage were more strongly correlated with frost tolerance than with field-based winter-hardiness. Although frost tolerance, fatty acid composition, proline content, and electrolyte leakage were significantly correlated with winter-hardiness, the rather low correlation values do not allow a general use of one of them alone to indirectly select for winter-hardiness.