THE USE OF CHLOROPHYLL FLUORESCENCE IN ASSESSMENT OF LOW-TEMPERATURE HARDINESS IN BLACK-CURRANT (RIBES-NIGRUM L)

The effect of freezing stress on chlorophyll fluorescence was examined in leaves of five genotypes of blackcurrant (Ribes nigrum L.). Minimum fluorescence (F(o)), variable fluorescence (F(v)) and the time for F(v) to decay to half its maximum value (q1/2) all varied between genotypes. Freezing stress significantly reduced F(o) in all genotypes, but the effect of freezing stress on F(v) 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 the cultivar 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 blackcurrant.