Similarity of the Conditions for Freeze-drying Preservation among Three Cucumoviruses

The conditions of preservation of three freeze-dried cucumoviruses were investigated. From analysis of the viral virions using sucrose density gradient centrifugation, there were some differences in its profiles among freeze-dried preparations of three viruses. Freezedried preparations of purified cucumber mosaic virus gave a smaller peak at the same position of the sucrose gradients compared with the untreated control. Some of the virions of chrysanthemum mild mottle or peanut stunt viruses swelled and their sedimentation rate was slower than that of untreated viruses. In the preparations of the viruses supplemented with sucrose or inositol, the alteration of the virus particles was completely prevented. Also, the effect of various additives and the rate of the decrease of infectivity were similar when the freeze-dried preparations were stored at 65°C for assessing promptly the effect of additives during the preservation. Consequently, these facts suggest that the viruses, which belong to the same group and have similar stabilizing forces of virions, may exhibit similar characteristics during the preservation by freeze-drying or by additives and could be preserved under the same conditions.