Abstract
Abstract: Stem rust caused by Puccinia graminis f.sp.tritici is a significant wheat production constraint in southeastern Ethiopia. Burkard 7-days volumetric spore trap was mounted in a field at Sinana Agricultural Research Center to examine the seasonal movement of urediospores of P. graminis f.sp.tritici during the cropping seasons of 2001-2006. Disease trap plots were also established to monitor the epidemics of stem rust on durum wheat at three major wheat growing and rust prone districts of Bale highlands viz., Sinana, Agarfa and Herero. Results showed that urediospores exist in the air throughout the year though the concentration considerably varied among the months and seasons, possibly because of the variation in weather condition and cropping time. The highest urediospores catch (613.8 - 2629.7 urediospores per m3 of air) was observed during the months of October/November-January. Number of urediospores per m3 of air was generally low but was rarely reduced to zero during the months of crop free period. Low to moderate levels of stem rust epidemics (not exceeding 30%) were recorded on durum wheat cultivars used for traps. Exceptions were at Sinana in 2001 and at Herero in 2002 and 2005 cropping seasons during which up to 60% stem rust severity levels were recorded. On the other hand, the level of stem rust severity (up to 80%) on some commercial bread wheat varieties included in this study for comparison revealed the development of high disease pressure. Durum wheat cultivars Cocorit 71, Gerardo, DZ 1928-2, DZ-2234 and CD 95759-11M showed resistant reaction to stem rust consistently over locations and years. This points to the existence of a high level of durable resistance in the tetraploid wheat species to the existing stem rust pathotypes in the most suitable environment for the development of the disease. Keywords: Durum Wheat; Epidemics; Stem Rust; Urediospores
Highlights
Cereal rusts are the most destructive diseases of wheat worldwide (Shaw, 1963; Haldore et al, 1982)
The study indicated that stem rust urediospores exist in the air almost throughout the entire year, the concentration varied depending on the time of cropping season and weather conditions
During the months of crop free period, the number of urediospores per m3 of air was generally low but was rarely reduced to zero. This is in agreement with previous findings by Saari and Prescott (1985) and Mamuluk (2000) who have reported the existence of local inoculum and endemic disease cycle all year round in the major epidemiological zones of the Africa south of the Sahara and southwestern Arabian Peninsula which includes Ethiopia, Kenya, Yemen, Tanzania and many other African countries
Summary
Cereal rusts are the most destructive diseases of wheat worldwide (Shaw, 1963; Haldore et al, 1982). Invariable epidemics of wheat stem rust have occurred in the major wheat growing areas of Ethiopia It became a major threat for Ethiopian wheat production after the epidemics of 1974 and 1992/1993 that eliminated bread wheat varieties known as Lacketch and Enkoy from production. Stem rust races prevalent in Ethiopia are among the most virulent races in the world (van Ginkil et al, 1989) with wide virulence spectrum and most frequent change in pathogenecity. This is more commonly observed in Arsi and Bale highlands, which are the wheat belt of eastern Africa
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