A study of Alternariosis, a seedborne disease of Zinnia elegans Jacq caused by the fungus Alternaria zinniae pape. : a thesis presented in partial fulfilment of the requirements for the degree of M. Agr. Sc.

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Massey University
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The ornamental zinnia (Zinnia elegans Jacg.), is one of the most popular of the late summer and autumn flowering annuals. The species originated in Mexico as a simple-headed flower type, and was later introduced to North America and Europe where new types were quickly created offering great variation in plant form and shades of blooms. In New Zealand the zinnia is particularly popular., being in great demand as a bedding plant for use in home gardens and public parks. Seedlings are raised commercially by nurserymen from seed imported mainly from Europe and North America. There have been widespread reports throughout New Zealand in recent years of severe losses in zinnia sowings from a disease characterised by post-emergence damping off due to stem lesioning at or above ground level, and severe spotting of foliage. Nursery conditions created by dense sowing, and the maintenance of high humidity within boxes by overhead watering seem to be conducive to rapid build-up and spread of the disease. Attacks have frequently been so severe as to render complete sowings unsaleable. The only foliage disease of zinnias recorded in New Zealand is Alternaria leaf spot caused by the fungus .ALTERNARIA ZINNIAE PAPE (Dingley and Brien 1956). In this report the authors describe symptoms on the foliage and stems of adult plants, and state some of the morphological and physiological properties of the casual organism. No mention is made of symptoms having been found in this country on seedlings, although they state the disease has been reported overseas as being seedborne, and causing a seedling blight as well as leaf spot symptoms on adult plants. [From Introduction]
Alternaria zinniae, Zinnia, Diseases and pests