Wheat leaf rust, triggered by Puccinia triticina Eriks (Pt), is among the most important diseases of wheat worldwide.  Deploying resistant varieties against leaf rust is the most effective, environmentally-friendly and economic way to control the disease.  In the present study, 66 wheat varieties form China and foreign countries were tested with 17 Pt races for gene postulation during the seedling stage in the greenhouse.  All the varieties were also planted to identify slow rusting responses to leaf rust at the adult plant stage in Baoding and Zhoukou field trials during the 2016/2017 to 2017/2018 cropping seasons.  Moreover, 12 closely linked molecular markers to known leaf rust resistance (Lr) genes were used for assessing all the varieties.  The results of both gene postulation and molecular marker identification showed that a total of eight Lr genes, Lr1, Lr10, Lr17, Lr20, Lr26, Lr34, Lr37 and Lr46, either singly or in combination were detected in 32 varieties.  Known Lr genes were not identified in the remaining 34 varieties.  Seventeen varieties were found to have slow rusting resistance.  The resistance sources identified in this study can be used as resources for resistance against leaf rust in wheat breeding programs in China and the respective foreign countries.

Wheat leaf rust, caused by Puccinia triticina (Pt), is an important foliar disease that has an important influence on wheat yield.  The most economic, safe and effective way to control the disease is growing resistant cultivars.  In the present study, a total of 46 wheat landraces and 34 wheat lines with known Lr (leaf rust resistance) genes were inoculated with 16 Pt pathotypes for postulating seedling resistance gene(s) in the greenhouse.  These cultivars and five wheat differential lines with adult plant resistance (APR) genes (Lr12, Lr22b, Lr34, Lr35 and Lr37) were also evaluated for identification of slow rusting resistance in the field trials in Baoding, Hebei Province of China in the 2014–2015 and 2015–2016 cropping seasons.  Furthermore, 10 functional molecular markers closely linked to 10 known Lr genes were used to detect all the wheat genotypes.  Results showed that most of the landraces were susceptible to most of the Pt pathotypes at seedling stage.  Nonetheless, Lr1 was detected only in Hongtangliangmai.  The field experimental test of the two environments showed that 38 landraces showed slow rusting resistance.  Seven cultivars possessed Lr34 but none of the landraces contained Lr37 and Lr46.  Lr genes namely, Lr9, Lr19, Lr24, Lr28, Lr29, Lr47, Lr51 and Lr53 were effective at the whole plant stage.  Lr18, Lr36 and Lr45 had lost resistance to part of pathotypes at the seedling stage but showed high resistance at the adult plant stage. Lr34 as a slowing rusting gene showed good resistance in the field.  Four race-specific APR genes Lr12, Lr13, Lr35 and Lr37 conferred good resistance in the field experiments.  Seven race-specific genes, Lr2b, Lr2c, Lr11, Lr16, Lr26, Lr33 and LrB had lost resistance.  The 38 landraces showed slow rusting resistance to wheat leaf rust can be used as resistance resources for wheat resistance breeding in China.