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

Mehmet Erhan Göre^*

Turkish Ministry of Agriculture and Rural Affairs, General Directorate of Agricultural Research, Plant Protection Research Institute, Genclik Cad. No: 6 35040 Bornova, Izmir, Turkey

^*erhangore@bzmae.gov.tr

Accepted for publication 03/09/07

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 Doidge. During April and May of 2007, in İzmir 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 (Figs. 1 and 3) 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 (Fig. 2). Microscopic observations revealed the urediniospore rust stage (Fig. 4). Urediniospores were ovoid or more or less globose, light brown, slightly echinulate, thin-walled with two conspicuous subequatorial pores, 19.3-28.9 x 17.2-24.3 µm. Based on morphological characters described above, this rust pathogen was identified as P. pelargonii-zonalis (Sivanesan, 1968).

Figure 1: Underside of Geranium leaf showing leaf spots of rust.	Figure 2: Top surface of geranium leaf showing chlorotic spot associated with leaf rust.

Figure 3: Underside of a leaf severely infected with geranium rust.	Figure 4: Typical urediniospore of P. pelargonii-zonalis.

Pathogenicity tests were conducted on 2-year-old P.  zonale plants, by spraying healthy leaves with a urediniospore suspension (2 x10⁵ spores per ml.) 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).

P. 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 and Raabe, 1979). Rust was first reported in Canada in 1976. This is the first report of this disease in Turkey.

References

Doidge EM, 1926. A preliminary study of the South African rust fungi. Bothalia 2, 1-228.

Harwood CA, Raabe RD, 1979. The disease cycle and control of geranium rust. Phytopathology 69, 923-927.

Sivanesan A, 1968. Puccinia pelargonii-zonalis. CMI Descriptions of Pathogenic Fungi and Bacteria No. 266. Wallingford, UK: CAB International.