Abstract

The effect of freezing stress on chlorophyll fluorescence was examined in leaves of black currant cultivars Baldwin, Ben Lomond, Golubka and Tombovskaya and the accession Ri-74020-6. Minimum fluorescence (F₀), variable fluorescence (F_v) and the time for F_v to decay to half its maximum value (q_1/2) all varied between genotypes. Freezing stress significantly reduced F₀ in all genotypes, but the effect of freezing stress on F_v was non-significant. Freezing stress significantly increased q_1/2, but the effect varied significantly between genotypes. The increase in q_1/2 induced by freezing stress was greatest in cv. Baldwin and least in the accession Ri-74020-6. The effects of freezing on chlorophyll fluorescence, particularly q_1/2, corresponded to the susceptibility of the genotypes to spring frosts. It is concluded that chlorophyll fluorescence can provide a rapid screening technique for assessing frost hardiness in black currant.