First Report of Leaf Rust by Puccinia triticina on Wheat in Oman

Wheat (Triticum aestivum L.), cultivated for forage and grain production, is an important crop in the Sultanate of Oman. In April 2005, leaf samples of an unknown local variety showing rust symptoms were collected from Rustaq, 100 km southwest of Muscat. Circular-to-oval, red-brown pustules, typical of uredinia, occurred mostly on the upper surface of leaves on plants nearing maturity. Telia with teliospores were observed on leaf sheaths. The disease was widespread in many fields and was likely to be limiting the yield. Urediniospores typical of Puccinia triticina Erikss. (=P. recondita Rob. ex Desm. f. sp. tritici) were roughly subglobose, measuring 18 to 28 × 20 to 25 μm, echinulate, with 3 to 8 scattered germ pores; teliospores were 2-celled, 34 to 50 × 15 to 17 μm, apex is chestnut brown, lower cell is light yellow, no germ pores (1,2). Pathogen identity was confirmed by nuclear ribosomal large subunit and internal transcribed spacer region-2 DNA analysis (voucher sequence deposited in GenBank, Accession No. DQ664194, voucher specimens deposited in the U.S. National Fungus Collections, BPI 872158 and 872159). Wheat is grown during the winter months in Oman and harvested in May. Although the disease was observed again in 2006, pathogen survival mechanisms are not presently clear, and current research is attempting to confirm its presence on alternate hosts, including grass weeds, and determine the distribution of the pathogen on local wheat land races and imported varieties. To our knowledge, this is the first documented report of P. triticina on wheat in Oman. Reference: (1) D. B. O. Savile. Fungi Can. 309:1, 1986. (2) M V Wiese. Compendium of Wheat Diseases. The American Phytopathological Society, St Paul, MN, 1987.