Geranium rust disease caused by Puccinia pelargonii‐zonalis : first report in Turkey

Geraniums are one of the most popular decorative plants for both indoor and outdoor use in Turkey. Many diseases and disorders can affect geraniums during the growing season. One of the most destructive foliar diseases that geraniums are susceptible to is geranium rust, caused by the fungus Puccinia pelargonii-zonalis. During April and May of 2007, in jzmir province of Turkey, symptoms of rust disease were observed on the leaves of Pelargonium zonale. The early symptoms of the disease were the formation of small, pale yellow spots on the undersides of leaves. These spots enlarged (5–8 mm) and turned rusty-brown indicating that spores were being released from the pustules. One or more partial-to-complete circles of pustules commonly developed around the original. Yellow spots opposite the pustules appeared on the upper leaf surface. Microscopic observations revealed the urediniospore rust stage. Urediniospores were ovoid or more or less globose, light brown, slightly echinulate, thin-walled with two conspicuous subequatorial pores, 19·3–28·9 × 17·2–24·3 µm. Based on morphological characters described above, this rust pathogen was identified as P. pelargonii-zonalis (Sivanesan, 1968). Pathogenicity tests were conducted on 2-year-old P. zonale plants, by spraying healthy leaves with a urediniospore suspension (2 × 105 spores mL−1) collected from actively sporulating pustules, suspended in 0·05% Tween 20, and filtered through four layers of sterile cheesecloth. Control plants were sprayed with sterile water. Inoculated plants were kept in a moist chamber (100% RH) for 2 days and then maintained a growth chamber at 20 ± 2°C, 75% RH with a 16 h photoperiod. After 13 to 15 days, inoculated plants developed rust symptoms, which were similar to those observed on naturally infected plants (Harwood & Raabe, 1979). Puccinia pelargonii-zonalis was first discovered on geranium in South Africa in 1926 (Doidge, 1926). By the 1960s it had spread to Australia, New Zealand, Europe and United States (Harwood & Raabe, 1979). This is the first report of this disease in Turkey.