Occurrence and pathogenicity of Puccinia triticina on wheat in South Africa during 2007

Abstract

A survey was conducted during 2007 to determine the occurrence and pathogenicity of Puccinia triticina Eriks., the cause of wheat leaf rust, in South Africa. Leaf rust was widely observed in the wheat growing areas of the Western Cape but only at a few localities in the Free State. A low incidence of leaf rust was detected at Cedara (KwaZulu-Natal). Leaf rust widely occurred within trap nurseries but it was observed only occasionally in farmers’ fields. Five pathotypes were identified from the total of 80 leaf rust samples collected. The most frequently detected pathotype was 3SA133 (76.8%) which was found in samples from all the localities followed by pathotype 3SA126 (11.0%). Other pathotypes detected were 3SA140 (7.3%), 3SA132 (3.7%) and 3SA137 (1.2%). None of the isolates tested was virulent on the resistance genes Lr3bg and Lr16 with the majority of the isolates (>73%) found virulent on the resistance genes Lr3a, 3ka, 11, 20, 24 and 30. No isolates avirulent on Lr1, 2c, 10 and 14a were found. The virulence patterns of pathotypes detected in 2007 was similar to those observed in previous seasons and new pathotypes were not observed. Thus, a significant change in the response of current commercial cultivars is not expected considering the results.