Leaf Rust Resistance In 56 Wheat Cultivars In China And Molecular Mapping Of Leaf Rust Resistance Genes In Mianyang 351-15

Wheat leaf rust, caused by Puccinia triticina, is widely distributed in the world for its wide range of climates adaptation. It is one of the most important diseases, and affected wheat production worldwide and in China. It occurs wherever wheat is grown, and can cause yield losses of wheat up to 5-15%. Using resistant cultivars is the most efficient, economic and environmentally-friendly way for reducing losses caused by leaf rust. It is very important to identify leaf rust resistance genes for breeding resistant cultivars. At present 68 leaf rust resistance genes have been formally designated in wheat. Most of them confer hypersensitive reactions and interact with the pathogen in a gene-for-gene fashion. The effectiveness of such genes is often short-lived in the field. Currently, only a few designated leaf rust resistance genes, such as Lr9, Lr19, Lr24 and Lr38, are effective against prevalent Chinese P. triticina pathotypes. It is very difficult to use only these several genes for durable control of wheat leaf rust in China. It is very important to research, map, and use leaf rust resistance genes in China wheat for breeding resistant cultivar and disease protection. The objective of this research was to identify seedling and slow rusting resistance to leaf rust in 56 wheat cultivars in China and map leaf rust resistance genes in Mianyang 351-15.In the study more than 800 wheat cultivars and advanced lines were collected from hebei, henan, shandong, anhui, and jiangsu province in China to test leaf rust resistance at adult stage in Henan and Hebei province. A total of 56 wheat lines with high resistance to leaf rust were selected to further research seedling and adult leaf rust resistance to Chinese P. triticina pathotypes. The 56 Chinese lines and 32 differential lines with known leaf rust resistance genes were inoculated with 13 pathotypes of P. triticina for postulation of leaf rust resistance genes effective at the seedling stage. These genotypes were also planted in the field for characterization of slow rusting responses to leaf rust in the 2008-2009 and 2009-2010 cropping seasons. Nine leaf rust resistance genes Lr26, Lr34, Lr1, Lr2a, Lr11, Lr20, Lr30, Lr33 and Lr44 were found in 36 wheat lines, whereas known resistance genes were not identified in the other 20 lines. Resistance gene Lr26 was present in 28 accessions. Lr1 and Lr20 were each detected in 6 entries, and 4 lines carried Lr30. Lr11 and Lr44 were each found in 2 cultivars. Lr2a, Lr33 and Lr34 were each present in one line. Forty six genotypes showed slow leaf rusting resistance in two cropping seasons. They can be used in breeding resistant cultivars with durable resistance to leaf rust.The resistance genes in Mianyang 351-15 were identified by comparing the reaction of Mianyang 351-15 to 15 Puccinia triticina races with 30 near-isogenic lines with known resistance genes. The result showed that Mianyang 351-15 was resistant to all the 14 species except P. triticina pathotype THTT. Mianyang 351-15 showed low ITs with all the Lr1-avirulent pathotypes indicated that Mianyang 351-15 maybe contained Lr1. The F1 and F2 plants from the cross of resistance line Mianyang 351-15 and susceptible line Zhengzhou 5389 were inoculated with pathotypes FHTT to test leaf rust resistance at seedling stage. The result showed the F2 population segregated for a single gene, fitting 3:1 ratio, indicating the resistance in Mianyang 351-15 was controlled by a dominant single gene. A total of 1273 pairs of SSR markers were screened between the parents, resistant and susceptible bulks. Linkage analysis was conducted with the software MapManager QTXb20. The resistance gene in Mianyang 351-15 was located on 5DL and linked to SSR markers Xbarc144 and Xwmc765 with genetic distances of 8.9 and 20.8 cM, respectively. Because Xbarc144 and Xwmc765 were close to Lr1, the STS marker WR003 co-segregated with Lr1 were used to test the F2 plants. The result indicated that WR003 was co-segregated with this resistance gene in Mianyang 351-15. Based on these results it can be concluded that Mianyang 351-15 contained Lr1 conferring the resistance to FHTT.