A 25-kDa dehydrin associated with genotype- and age-dependent leaf freezing-tolerance in Rhododendron: a genetic marker for cold hardiness?

Dehydrins are plant proteins that may play a critical role in stabilizing c ell functions during freezing and other dehydrative stresses. This study ex amines whether dehydrin expression in leaves is associated with varying lev els of freezing-tolerance among F-2 segregants, species, and cultivars of e vergreen Rhododendron. Experiments were also conducted to determine whether physiological and chronological aging affects freezing-tolerance and dehyd rin accumulation in Rhododendron leaf tissues. Our results indicate that in cold-acclimated F-2 populations, levels of a 25-kDa dehydrin were closely associated with differences in leaf freezing-tolerance (LFT) among segregan ts Studies of wild and cultivated plants indicated that LFT increased with both chronological age and developmental phase-change (juvenile to mature p lants) and that this trend was accompanied by increased accumulation of the 25-kDa dehydrin. It is suggested that presence or absence of the 25-kDa de hydrin could serve as a genetic marker to distinguish between super cold-ha rdy and less cold-hardy rhododendron genotypes. Similarly, the relative lev el of this protein within a genotype can serve as a physiological indicator of freezing-tolerance status under a range of phenological (acclimation) o r developmental (age) conditions.