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1972 - 19732

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Subject: search.filters.subject.Chrysanthemums

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    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
    (Massey University, 1972) Lunn, David William
    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.
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    Flower blight of chrysanthemums : the causal fungi and their control : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science at Massey University
    (Massey University, 1973) Singh, Gurmit
    The commercial chrysanthemum commonly grown in New Zealand is botanically identified as Chrysanthemum morifoliurr. Ramat. and is believed to have originated in China. As the family name Compositae suggests the individual flower ('flower head') is a composite arrangement of two types of florets, namely ray florets with well developed petals, and disc florets with tubular or poorly developed petals. Production of commercial chrysanthemums basically comprises three categories: (i) cut flowers; (ii) cuttings; (iii) container or pot plants. Chrysanthemums are probably grown by more floriculturalists than any other flower crop. Much of its popularity is attributed to the wide range of colours and forms and the fact that it can be grown either as a pot plant or for cut flowers. Another important characteristic of the chrysanthemum is the long keeping quality of the flowers, a feature which is much appreciated by retailers and consumers. In the United States of America the chrysanthemum or 'mum' is the most popular flower, surpassing both the rose and carnation in total wholesale value. [FROM INTRODUCTION]