POSTHARVEST QUALITY OF CUT ROSES FOLLOWING ELECTRON-BEAM IRRADIATION

Cut Rosa xhybrida L. 'Royalty' flowers were used to determine the effi cacy of electron-beam irradiation for increasing postharvest quality a nd decreasing petal infection by Botrytis cinerea Pers. In an experime nt for determining the injury threshold, roses received electron-bean irradiation of 0, 0.5, 1, 2, and 4 kGy. Irradiation dosages greater th an or equal to 1 kGy caused necrosis on petal tissue and decreased pos tharvest life at 20 degrees C. In a second experiment to evaluate post harvest quality, roses were irradiated at 0, 0.25, 0.5, 0.75, and 1 kG y. Dosages of 0.25 and 0.5 kGy slowed the rate of flower bud opening f or 2 days but did not decrease postharvest quality when compared with nonirradiated roses. Roses that received irradiation dosages of 0.75 a nd 1 kGy showed unacceptable quality. In a third experiment, roses tha t had or had not been inoculated with B. cinerea were irradiated 0, 0. 25, 0.5, and 0.75 kGy. Irradiation did not control B. cinerea populati ons, and rose quality decreased as dosage increased. In a fourth exper iment to determine the effect of irradiation on B. cinerea, conidia on water-agar plates exposed to dosages less than or equal to 1, 2, and 4 kGy germinated at rates of approximate to 90%, 33%, and 2%, respecti vely, within 24 h.