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Occurrence of Rust Disease Caused by Puccinia lagenophorae on Cineraria in the Americas

Cineraria (Pericallis × hybrida B. Nord.), sometimes referred to as Senecio cruentus (Masson ex L'Hér.) DC., Asteraceae, is native to the Canary Islands. This important ornamental plant is cultivated worldwide and is of significant economic importance in the United States as a flowering potted plant. In February 2002, rust pustules were observed on cineraria plants cultivated in a greenhouse in Suffolk County, New York. The rust was identified as Puccinia lagenophorae Cooke (2). Aecioid sori were up to 1 mm in diameter and densely clustered, yellowish, and amphigenous but mainly hypophyllous on swollen, rounded, infected areas. The peridium is cupulate, lacerate, and composed of colorless cells measuring 10.5 to 20 × 18 to 33 μm that are verrucose on the outer surface and finely verrucose on the inner surface. Spores are sessile, 12 to 18 × 10.5 to 17 μm, yellowish, minutely verrucose with conspicuous, loosely attached globules, and in long chains in fresh material. Telia were not observed. Signs and symptoms were reproduced by rubbing healthy leaves of Pericallis × hybrida with a rust-infected leaf of Pericallis × hybrida bearing aecia sori. Plants were enclosed in a plastic bag for 18 h and held at 21°C. Aecioid sori developed within 10 days. Voucher specimens have been deposited in the U.S. National Fungus Collection (BPI 841952 and 841953). Common groundsel (S. vulgaris L.) infected by P. lagenophorae was observed outside the greenhouse in which the infected cineraria were discovered (W. L. Bruckart and A. Senesac, unpublished), and we postulated that the cineraria in the greenhouse might have been infected by spores from those infected weeds. Cross-infectivity was tested by rubbing leaves of groundsel on which aecia sori of P. lagenophorae were present on five leaves on each of three healthy cineraria plants. Incubation conditions were the same as described above. Aecioid sori developed 10 days after inoculation on four leaves of one plant. The control plants remained healthy. The inoculation was repeated on two plants and aecia sori developed on leaves of both plants. To our knowledge, this is the first report of P. lagenophorae on cineraria in the Americas. P. lagenophorae is autoecious, native to Australia and New Zealand, and has approximately 60 known host species (2). Recently, it was reported in California on common groundsel (3) and English daisy (Bellis perennis L.) (1).

References: (1) S. T. Koike and M. Scholler. Plant Dis. 85:562, 2001. (2) M. Scholler. Sydowia 49:177. 1997. (3) M. Scholler and S. T. Koike. Plant Dis. 85:335, 2001.