ISHS Acta Horticulturae 234: VII International Symposium on Virus Diseases of Ornamental Plants
INVESTIGATION OF THE ETIOLOGY AND CYTOLOGY OF CHRYSANTHEMUM SLOW DECLINE |
| Authors: | M.M. Dienelt, R.H. Lawson |
| Abstract:
Chrysanthemum morifolium cultivars 'White Sands', 'Mountain Peak', 'Mountain Snow', and 'Red Fandango' affected with chrysanthemum slow decline were investigated for the presence of mycoplasma-like organisms (MLO) or other fastidious prokaryotes. Plants with leaf strapping, rugosity and raised veins characteristic of severe decline were treated with oxytetracycline but symptom remission did not occur. Symptoms were not induced in healthy or mild decline plants grafted to rootstocks of severely affected plants. Electron microscopy revealed more extensive phloem disruption in symptomatic than healthy tissue, with vesicular, apparently degenerative structures present in central vacuoles of xylem and phloem parenchyma, companion cells, and sieve elements. Paramural bodies appeared as plasmalemma and/or tonoplast invaginations or as discrete bodies within cytoplasm and central vacuoles and membranes developed between cell walls and plasmalemmae and in central vacuoles. Membrane and paramural body proliferation appeared most prominent in companion cells of CSD-affected plants. Bundle sheath and paslisade cells contained cell wall appositions and electron dense material in central vacuoles that were observed only in symptomatic tissue. While chrysanthemum slow decline appeared to affect cell walls and plasmalemmae, abnormalities could not be attributed to presence of a pathogen. | |
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