Postulation And Molecular Detection Of Wheat Leaf Rust Resistance Genes Of Commercial Wheat Cultivars In China

Wheat is a cultivated crop worldwide now and the production of wheat is the sencond most-produced cereal crop after maize. Wheat leaf rust, caused by Puccinia triticina, is one of serious fungal diseases and distributed widely in the world. It also affected high and stable yield of wheat in China. Wheat leaf rust occurred every year in different regions and severities varied under different environment between areas. The virulence mutation evolutes fast and the selection causes new pathotype variation of leaf rust pathgens, which often overcome existing leaf rust (Lr) resistance genes. The case is that it is usually unknown for Lr resistance genes before the cultivar is released and the breeders pay less attention about leaf rust resistance in their breeding process in China. In order to find out the gene(s) combination and resistance features in 116 important wheat commercial varieties, gene postulation and molecular detection have been carried out, which provided a reasonable basis for the cultivar application and disease control.Twenty-eight leaf rust near isogenic lines in thatcher background and 16 single-gene lines with known leaf rust resistance genes were used as differential hosts in this study. A total of 116 Chinese winter wheat cultivars were inoculated with 28 pathotypes of Puccinia triticina for postulation of leaf rust resistance genes effective at the seedling stage. Molecular markers that are closely linked or co-segregated with wheat leaf rust resistance genes Lr9, Lr10, Lr19, Lr20, Lr21, Lr24, Lr26, Lr29, Lr34, Lr35 and Lr38, were for further identification of the molecular assisted with Chinese winter wheat cultivars. The results indicated that resistance gene Lr26 was present in 43 accessions. Lr3 and Lr3bg were each found in sixteen cultivars. Genes Lr13 and Lr34 were each detected in Yumai 54. Lr11 and Lr13 were each present in 04zhong 3604, and thirteen lines possessed Lr1. Lr27+31+10 was identified in nine lines.Twelve cultivars were postulated to possess Lr2c. Lr13 may exist in Xinmai 19. Lr19 may present in Zhongliang 26. Lr30 may exist in Zhongliang 9589. Lr34 was detected in Lantian 12. Thirty-seven cultivars may carry unknown resistance genes to leaf rust. Lr9, Lr10, Lr20, Lr21, Lr24, Lr29 and Lr35 were not present in the tested 116 accessions.Multiplex PCR was developed and optimized for detection of Lr gene combination of Lr9-Lr26 and Lr19-Lr20. The gene presence was analyzed in 116 Chinese winter wheat cultivars or lines. Data from PCR markers were confirmed by seedling resistance profiles to 28 isolates with different virulence spectra. The results were consistent for wheat leaf rust resistance genes when the STS markers were used separately. This method was proved to be repeatable and low cost for evaluation of wheat resistance genes in wheat cultivars. The multiplex PCR technique may be efficiently used in marker-assisted selection for wheat breeding and useful for the DNA-based identification of wheat varieties.