First Report of Rust Caused by Puccinia allii on Wild Garlic in California

Wild garlic (Allium vineale) is a bulbous perennial weed that was introduced from Europe and is now established throughout the eastern and much of the western United States. In 2001, wild garlic plants growing in Monterey County, CA were infected with a rust fungus. Uredinia and telia were present on leaves, resulting in small (2 to 5 mm long) lesions; however, leaf dieback and other symptoms were not observed. The orange urediniospores were spherical to ellipsoidal, echinulate, and mea-sured 26 to 30 × 25 to 28 μm. Telia were black in mass and divided into locules by fused paraphyses. Teliospores were located within the locules and were brown, smooth-walled, two-celled, and measured 40 to 50 × 17 to 20 μm. Teliospore pedicels were hyaline, usually fractured, and measured 3 to 15 μm. One-celled mesospores were not observed. Based on these morphological characteristics, the pathogen was identified as Puccinia allii (1,2). To our knowledge, this is the first report of rust caused by P. allii on wild garlic in California. Because of this finding, an experiment was designed to determine whether wild garlic could be a source of rust inoculum for commercial allium crops. Wild garlic bulbs were planted in 4-in. pots (10 cm square) and grown in a greenhouse. At the 4- to 5-leaf stage the plants were transplanted in a garlic (Allium sativum) cultivar trial that had been inoculated with an isolate of P. allii from garlic. When plants were evaluated 2 months later, uredinia and telia were observed on the wild garlic plants, and the fungus was confirmed to be P. allii. Wild garlic, therefore, could be a source of overwintered inocula for the rust disease that occurs on commercial garlic and onion (A. cepa) in California (2). References: (1) D. M. Jennings et al. Mycol. Res. 94:83, 1990. (2) S. T. Koike et al. Plant Dis. 85:585, 2001.