First Report of Alternaria porri on Garlic in South Africa. Theresa A. S. Aveling, Margaretha Mes Institute for Seed Research, University of Pretoria, Pretoria 0002. S. P. Naude, V.O.P.R.I., Private Bag X293, Pretoria 0001, South Africa. Plant Dis. 76:643. Accepted for publication 30 December 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0643A.
A leaf disease of garlic (Allium sativum L.) causing severe foliage damage was recurrently observed in the Natal and Transvaal provinces of South Africa. Leaf symptoms varied from small, elliptic white lesions to large, sunken purple lesions with concentric dark and light zones where sporulation was heavy or sparse, respectively. Alternaria porri (Ellis) Cif., the causal organism of purple blotch of garlic and onion, was consistently isolated from both types of lesions and from diseased leaf tips that were dying back. Pathogenicity of an isolate of A. porri from a garlic leaf (deposited with the National Collection of Fungi, South Africa, designated PREM 50716) was shown by inoculating leaves of 25 garlic plants (cv. Large Egyptian White). Inoculated plants were placed in a mist chamber for 12 hr, then returned to the glasshouse. After 9 days, symptoms resembling those observed in the field were apparent. A. porri was reisolated from these plants and produced cultures identical to those of the original isolate. Our observations indicate that heavy dew or rain at any time of the year encourages the development of purple blotch of garlic.