AbstractThe 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 (Fv) and the time for Fv to decay to half its maximum value (q1/2) all varied between genotypes. Freezing stress significantly reduced F0 in all genotypes, but the effect of freezing stress on Fv was non-significant. Freezing stress significantly increased q1/2, but the effect varied significantly between genotypes. The increase in q1/2 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 q1/2, 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.