Effectiveness of leaf rust resistance genes against Puccinia triticina populations in Western Siberia during 2008–2017

Abstract

A monitoring survey focused on the local leaf rust pathogen on spring bread wheat was conducted during 2008–2017 in the Western Siberian region of the Russian Federation. Resistance genetics in cultivars released in the region during the last twenty years has been limited to only a few Lr genes: Lr1, Lr9, L10, Lr26, and Lr34. The effectiveness of Lr genes was assessed in field tests of 38 «Thatcher» Near Isogenic Lines (NILs). Resistance genes were classified into four groups based on infection types (ITs) in response to the local population of Puccinia triticina. Lines carrying genes Lr17, Lr18, Lr24, Lr25, Lr29, Lr35, Lr37, Lr44, and LrW(52) remained almost free of infection for the whole duration of rating. Their disease scores did not exceed the level of medium resistant even in seasons favorable for the spread of leaf rust. ITs indicative of moderate resistance were revealed in lines carrying genes Lr12, Lr13, Lr28, Lr34, and Lr38, except under conditions favorable to infection when plants became susceptible. Genes Lr1, Lr2a, Lr2c, Lr9, Lr14a, Lr14b, Lr15, Lr16, Lr19, and Lr22 showed reduced effectiveness against leaf rust in the region during the monitoring dates. Virulence to lines carrying genes Lr2b, Lr3, Lr3bg, Lr3 ka, Lr10, Lr11, Lr20, Lr21, Lr26, Lr30, Lr32, Lr33, and LrB was recorded during the whole time of monitoring from 2008 to 2017. Since race-specific genes Lr24 and Lr29 are still effective in the Western Siberian region, they may be recommended for breeding purposes deployed in combination with slow rusting gene Lr34 and the race-specific adult plant resistance genes Lr12 and/or Lr13, to provide durable resistance.