Bunts and smuts of wheat in North Africa and the Near East

Abstract

Bunts [common bunt (Tilletia laevis and T. tritici) and dwarf bunt (T. controversa)] and smuts [loose smut (Ustilago tritici) and flag smut (Urocystis agropyri)] of wheat are important cereal diseases in most countries of north Africa and the Near East. There are no peculiarities in the occurrence of bunts and smuts, except for dwarf bunt, which is limited to high-altitude areas of Turkey, Iran and Iraq. Host adaptation, rather than topography, determines the distribution of the common bunt pathogens: ir: laevis predominates in bread wheat, whereas T. tritici attacks both bread and durum wheat non-preferentially. Incidence of bunt-and smut-affected wheat heads is generally low, however the frequency of their occurrence in fields is high, indicating their potential threat. Some bunts and smuts occur on hosts other than wheat, for example, nag smut on Aegilops crassa, loose smut on Ae. geniculata and rye, and dwarf bunt on Hordeum and Aegilops spp. Genetic variability of the pathogens causing common bunt and loose smut was investigated. Chemical seed treatment is the most widely used control for bunts and smuts. Organic nutrients as seed treatments to control common bunt of wheat show considerable promise. Sources of resistance to loose smut, and common and dwarf bunts of wheat, are available in wheat and its wild relatives. Triticum boeoticum, T. dicoccoides, and Aegilops species represent excellent sources of resistance to common bunt. There are three major sources of resistance in durum wheats, Senatore Cappelli and Haurani, Jenneh Khetifa, and Mindum. Common bunt resistance genes Bt5, Bt6, Bt8, Bt9, Bt10, and Bt11, and several undescribed resistances remain effective in the screening field at ICARDA, Syria.