Virulence of Puccinia triticina races collected on durum wheat in Spain during 2009-2015

Leaf rust is an important worldwide disease on wheat caused by the fungus Puccinia triticina. Great infections on durum wheat occurred in Southern Spain in the 2000s but diminished in recent years due to deployment of resistant varieties and application of fungicides by farmers. A leaf rust survey was carried out from the 2009-15 period to monitor the virulence spectrum of the prevailing pathotypes. A total of 84 leaf rust isolates were collected on durum wheat fields. From those, single culture were obtained and used to inoculate a set of 27 differential isolines of the susceptible variety Thatcher. In addition 8 durum varieties with known Lr genes were also included.
The main highlight is that the resistance conferred by the popular Lr14a gene was broke up in 2013, but since then virulence to this gene is not widespread. In total, 23% of the isolates were virulent to the lines containing Lr14a. Lr1, Lr3, Lr3bg, Lr16, Lr24, Lr26, and Lr28 are very effective. Lines carrying Lr2c, Lr10, Lr14b, Lr20, Lr23, and LrB displayed susceptibility to most isolates. The durum varieties Jupare (Lr27+Lr31), Guayacan (Lr61), Storlom (Lr3+) and Camayo (LrCam) are also resistant against all isolates tested. Diversification of Lr genes is needed in the coming varieties to delay the appearance of new virulent races.