UV-C irradiation induces defence responses and improves vase-life of cut gerbera flowers

Abstract

UV-C ( λ = 254 nm) irradiation was effective in reducing Botrytis cinerea floret specking (i.e., lesion development) and maintaining a better postharvest quality of cut gerbera flowers. A range of UV-C doses (0.5–10.0 kJ m −2) was tested on ‘Ice cream’ and ‘Ecco’ gerbera flowers to activate germicidal and inducible defence mechanisms. Irradiation of B. cinerea cultures with 0.5, 1.0, 2.5 and 5.0 kJ m −2 UV-C resulted in up to a 10-fold reduction of conidial germination percentages and significant ( P < 0.05) delay of mycelium growth, compared to the non-irradiated control cultures. Moreover, lesion diameters on gerbera florets inoculated with UV-C irradiated B. cinerea cultures were reduced by up to 70%, suggesting that UV-C had a negative effect on the pathogenic strength of the fungi. Lesion diameters on florets of UV-C irradiated gerberas were reduced by up to 55% giving evidence that defence responses in the host tissue were induced. Concentration of total phenolics seemed to be unaffected by 0.5 kJ m −2 UV-C treatment in both cultivars, but polyphenol oxidase (PPO) activity increased and remained higher compared to the non-irradiated control flowers throughout the 48 h storage period at 20 °C. The increase of PPO suggests that this enzyme might play an important role in host defence mechanisms that suppressed B. cinerea floret specking. Gerbera flowers irradiated with 1.0 or 10.0 kJ m −2 UV-C showed improvement in vase-life by 1.8 and 2.4 d, decrease in stem break percentages by 43 and 29% and delay in stem break incidence by 3.3 and 1.3 d, respectively.