ISHS Acta Horticulturae 110: V International Symposium on Virus diseases of Ornamental Plants
HYDRANGEA VIRESCENCE: SYMPTOM SUPPRESSION IN PLANTS INFECTED WITH THE MYCOPLASMALIKE ORGANISM (MLO) ASSOCIATED WITH MILD DISEASE CHALLENGE INFECTED WITH THE SEVERE DISEASE MLO |
| Authors: | R.H. Lawson, F.F. Smith |
| Abstract:
Severe hydrangea virescence is a lethal disease of Hydrangea macrophylla (florists' hydrangea). Plants with the severe form of the disease are stunted with small leaves, vein yellowing, and very dwarfed, green cymes. Hydrangeas with mild virescence produce leaves that expand normally without symptoms. Cymes on the infected plants have large, all-green florets. Each form of the disease remained stable for more than 3 years through repeated transfer of the causal agents by budding to the same seedling clone. Healthy hydrangea seedlings inoculated with the severe virescence agent died a few months after inoculation. Plants infected with the mild virescence agent and challenge inoculated with the severe agent showed mild vein yellowing and the leaves expanded normally. Vein yellowing disappeared on expanded leaves. Mycoplasmalike bodies (MLO's) were commonly observed in plants with severe virescence only, but MLO's were found infrequently in challenge inoculated plants. Severe and mild virescence are apparently caused by related MLO's. | |
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