Virus diseases of chrysanthemums in the Manawatu : a thesis presented in partial fulfilment of the requirements for the degree of Master of Horticultural Science (in Plant Science) at Massey University
Loading...
Date
1972
DOI
Open Access Location
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Massey University
Rights
The Author
Abstract
A survey of the virus diseases of chrysanthemums in the Manawatu revealed that tomato as penny virus (TAV) and chrysanthemum stunt were present in most cultivars grown for cut-flowers, often resulting in unmarketable flowers. Latent infection of both viruses was revealed in most cultivars tested by sap or graft indexing to suitable indicator plants. Rod-shaped particles of the leaf mottle group were observed in leaf-dip electron microscopic examinations from most cultivars examined, although leaf symptoms were not widespread. Characterisation of TAV revealed that the virus could be sap and graft transmitted and was aphid transmitted in a stylet-borne manner. Host range and in vitro properties of TAV did not differ sufficiently from overseas reports to warrant the designation of a new strain of TAV. The addition of DIECA to chrysanthemum triturates markedly increased the infectivity of TAV in chrysanthemum sap. Graft indexing for chrysanthemum stunt, using the cultivar 'Mistletoe' was found to be more reliable then sap inoculation to either 'Mistletoe' or cineraria, or the starch local lesion test. Defoliation of the 'Mistletoe' scions reduced the latent period of chrysanthemum stunt from 4 to 2 months. The presence of rod-shaped particles ca. 690 x 15 nm in leaf-dips from many chrysanthemums, and from inoculated petunia leaves showing yellow local lesions suggested the presence of one or more of the leaf mottle viruses. Graft indexing with 'Good News' chrysanthemums gave symptoms of mosaic infection similar to those described in the U.S.A., suggesting a relationship between the mosaic and leaf mottle groups. The leaf mottle virus infecting chrysanthemums in the Manawatu was found to be aphid transmitted and of the non-persistent or stylet-borne type. Erratic symptom expression in Petunia hybrida Vilm, necessitated the. use of leaf-dip examinations to determine the presence of virus particles in the inoculated petunia leaves during the assessment of the in vitro properties of the leaf mottlo group. Suggested control measures include indexing to obtain virustested chrysanthemum stock plants, and the prevention of re-infection from outside sources by the aphid vectors. Preliminary investigation showed that meristem-tip culture is feasible for elimination of TAV and viruses of the leaf mottle group from totally infected chrysanthemum cultivars, but that treatment during "hardening off" is critical for plantlet survival.
Description
Keywords
New Zealand -- Manawatu District, Chrysanthemums, Diseases and pests