Department of Crop Sciences, Sultan Qaboos University, Box 34, Al Khod 123, Oman
Plant Pathology Laboratory, Jimah Agricultural Research Station, P.O. Box 540, Bahla - 612, Oman
USDA-ARS, SBML, 10300 Baltimore Ave, Beltsville, MD 20705
Maize (Zea mays L.) is an important annual forage crop cultivated in the Sultanate of Oman, especially during the summer months. It is used for green fodder and grains and often intercropped in fruit orchards, especially under date palms. In April of 2005, leaf samples showing rust symptoms were collected from Samail, 100 km south of Muscat. Oval-shaped, red-brown pustules covered both sides of the leaves and yielded urediniospores typical of Puccinia sorghi Schwein. Urediniospores were roughly subglobose, measured 23 to 28 × 20 to 25 μm, echinulate, with three or four equitorial germ pores (2). Teliospores (38 to 42 × 16 to 19 μm) were observed, but few in numbers, most probably because of the time of year of collection. Pathogen identity was confirmed by nuclear ribosomal large subunit (28S) and internal transcribed spacer region 2 (ITS-2) DNA analysis (voucher sequence deposited in GenBank, Accession No. DQ345724, voucher specimen deposited in the U.S. National Fungus Collections, BPI 871134). P. sorghi has previously been reported from Yemen and Saudi Arabia (1) but not from Oman. Maize is grown throughout the year in Oman, and pathogen survival probably does not require the presence of the alternate host, nonetheless, Oxalis species are present and current research is attempting to locate and confirm the presence of the aecial stage in Oman.
References: (1) CMI Distribution Maps of Plant Diseases. Map No. 279. Ed. 4. CABI, Wallingford, UK, 1978. (2) D. G. White, ed. Compendium of Corn Diseases. The American Phytopathological Society, St Paul, MN, 1999.