Analysis of the ascorbate antioxidant pathway in overwintering populations of lucerne ( Medicago sativa L.) of contrasting freezing tolerance.

A recurrent selection protocol, entirely performed under environmentally controlled conditions, was applied to develop lucerne populations selectively improved for their tolerance to freezing (TF populations). Several cycles of recurrent phenotypic selection have been performed in various genetic backgrounds and new populations have been produced using elite genotypes. TF populations obtained after successive cycles of selection for improved freezing tolerance allowed the understanding of the relationship between cold-induced changes, such as the antioxidant metabolism, and the ultimate level of freezing tolerance of lucerne. Major findings obtained from the research are discussed in this chapter.