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Epidemiology and Specialization of Wheat and Oat Stem Rusts in Kenya in 1968. G. J. Green, Formerly advisor for the Canadian International Development Agency-University of Manitoba Kenya Project, now Plant Pathologist, Canada Department of Agriculture, Research Station, 25 Dafoe Rd., Winnipeg 19, Manitoba; J. W. Martens(2), and O. Ribeiro(3). (2)Formerly advisor for the Canadian International Development Agency-University of Manitoba Kenya Project, now Plant Pathologist, Canada Department of Agriculture, Research Station, 25 Dafoe Rd., Winnipeg 19, Manitoba; (3)Formerly Agricultural Officer (Research), Plant Breeding Station, Njoro, Kenya, now Graduate Research Assistant, Department of Plant Pathology, University of West Virginia, Morgantown, West Virginia 26506. Phytopathology 60:309-314. Accepted for publication 15 September 1969. DOI: 10.1094/Phyto-60-309.

Urediospores of Puccinia graminis and P. recondita were trapped at Njoro, Kenya, from February to December 1968. The initiation of rust development in the area can be explained by this inoculum. Lolium multiflorum was infected with rye stem rust, and Agrostis producta, Dactylis glomerata, and two unidentified grasses were infected with oat stem rust. No grass infected with wheat stem rust was found. Using new sets of differential hosts and new systems of nomenclature, seven races of wheat stem rust and four races of oat stem rust were identified in East Africa in 1968. Wheat stem rust race EA5 predominated, presumably because it can attack the widely grown cultivar Romany. Oat stem rust race EA3 predominated. It attacks varieties carrying most of the identified resistance genes. There are good sources of resistance to wheat stem rust, but no commercial hexaploid oat variety is resistant to all races of stem rust.