First record of leaf rust caused by Puccinia hordei on Hordeum vulgare subsp. spontaneum in Turkey

In spring 2003, a leaf rust caused by Puccinia hordei was found on a wild barley species, Hordeum vulgare subsp. spontaneum (HVS), in the Sanliurfa province, southeastern Anatolia District. Pustules (uredosporangia) occurred on the upper leaf surfaces, leaf sheaths and occasionally lower leaf surfaces. The pustules were commonly 1-4 mm across, oval to round and light brown in colour. Low numbers were seen on the flag leaf, progressively increasing on older, lower leaves. Uredospores were egg-shaped to spherical, yellow and 28-36 µm by 24-28 µm. Teliosporangia commonly occurred on the lower surface of older leaves and usually contained two-celled mesospores, occasionally one-celled. These features were used to identify Puccinia hordei, the cause of brown leaf rust.

Freshly harvested urediospores were used to prepare a spore suspension, adjusted to 4 x 10⁵ spores per ml with 5 g of talcum powder per ml. This suspension was sprayed onto twenty day-old seedlings of HVS (two leaf stage), which were then put into a moist chamber maintained at around 100% relative humidity for 16h at 20 ± 1°C. After this period, the chamber was then partially opened and plants allowed to dry slowly, before moving them into a greenhouse at 22 ± 3°C. Similar treatments were performed on control plants, sprayed with sterile water only. Lesions similar to those observed in the field occurred within two weeks on the plants sprayed with the spore suspension. The control plants remained healthy.

P. hordei occurs widely on HSV in Israel (Manisterski et al. 1986; Manisterski & Anikster, 1994) and successful artificial infections have been achieved (Moseman et al., 1990). This is however the first record of brown leaf rust on HSV as a wild host in Turkey, where P. hordei occurs occasionally in the coastal districts (Karaca, 1965). This record is significant in the search for natural sources of resistance to a disease which causes widespread losses to cultivated barley (H. vulgare) worldwide.