Physiological specialization of Puccinia triticina on wheat in Argentina, 2013

Leaf rust is the most important wheat disease in Argentina; 4.2 M ha of wheat were grown in 2014. The objective of the study was to identify avirulence/virulence phenotypes of the Pt population in leaf rusted samples collected in wheat-growing areas during 2013. Single uredinial isolates were taken from samples and tested on Thatcher near-isogenic lines and some local varieties. Resistance genes in sets of four included: Lr1, Lr2a, Lr2c, Lr3; Lr9, Lr16, Lr24, Lr3ka; Lr11, Lr17, Lr30, Lr10; Lr14a, Lr19, Lr20, Lr21; Lr23, Lr25, Lr26, Lr27+31; Lr29, Lr36, Lr39/41, Lr42, Lr43; Lr44 and Lr47. Race designations were based on the first three sets proposed by Long and Kolmer (1989, Phytopathology, 79: 525-529) and the gene designations Lr10 and/or Lr20 were appended to indicate virulence on lines with those genes. Among 141 single uredinial isolates, 18 races were identified. Race MFP, was the most frequent, accounting for 27% of isolates; race MDP was second at 22.7%. Both races were isolated for the first time in 2005. The first three races were present in similar frequencies to 2012. Two new races were found, MKJ 10 and MGJ 10. Virulence was not found for genes Lr19, Lr21, Lr25, Lr29, Lr36, “Lr43”, Lr44 and Lr47. Race DBB 10,20 was the most frequent race on durum wheat. Virulence to Lr16 appears to be increasing.

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National Institute of Agricultural Technology (INTA), Argentina
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