Incidence and Exression of Cymbidium Mosaic Virus in Dendrobium Hybrids

Abstract

The incidence of cymbidium mosaic (CyMV) virus and its effect on yield and necrotic symptom expression in flowers were investigated in Dendrobium cultivars and selections. The percentage of plants infected with CyMV was found to increase linearly with time spent in cultivation. Infection increased approximately 15% per year for plants 4 to 7 years of age. Differences in flower spray yield between CyMV-infected and non-infected plants were not significant at the 5% level. However, in three groups of plants, the reduction in yield was significant at the 15% level suggesting that flower yields might be depressed in CyMV-infected plants. Necrotic symptoms in flowers were found to be highly correlated with CyMV infection in 3 commercial dendrobium cut-flower cultivars. A small number of resistant plants were found in all three cultivars. Dendrobiurn Jaquelyn Thomas 'Uniwai Supreme' was found to have the highest percentage of resistant plants. A large amount of variability in the expression of flower necrosis was found among various Dendrobium cultivars and selections. Expression ranged from 0 to 100% necrotic flowers at various stages of raceme maturity. Expression patterns were consistent within plants and among related plants. This suggests that genetic variability for resistance to CyMV-induced flower necrosis exists in Dendrobium.