Molecular Markers And Gene Location For A Stripe Rust Resistance Gene YrVir1 In Chinese Wheat Differentials Virgilio

Wheat stripe rust, caused by Puccinia striiformis West. f. sp. Tritici (PST), is one of the most destructive diseases on wheat in many wheat-grown regions in the world, and China is the biggest epidemic region of wheat stripe rust. PST is relatively independent epidemic region in China compared with others. The wheat cultivars became susceptible after widely grown for several years to the new virulent pathotypes of PST. Therefore, it's useful to pay attention to identify PST pathotypes. The identification method with resistance genes in differential hosts is most effective in practice to monitor the virulence of PST. After finding the genetic traits of resistance genes in differential hosts and developing the corresponding molecular markerswe can detect the variation of stripe rust races and analyze wheat resistance on a molecular level. The cultivar Virgilio is one of wheat differential hosts for stripe rust in China. It is important to localize and develop markerfor its resistance genes to stripe rust.By conventional genetic method, the resistance genes in differential Virgilio were transferred to susceptible cultivar Taichung29 to develop near isogenic lines(NILs) Taichung29*6/Virgilio and four lines (N296, N300, N304 and N312) were obtained. Taichung29*6/Virgilio lines, served as resistance donors, were crossed with the recurrent cultivar Taichung29 respectively, and the resulting F₁ were self-pollinated to produce the F₂ population. We also made testcross to construct a BC₁ segregating population. Through seedling resistance identification of the parents, F₂ and BC₁ population and statistics analysis, we identify the resistance gene number and its genetic characteristics of the Taichung29*6/Virgilio lines corresponding to the pathotype 2E16 of P. striiformis. We localized the resistance genes in Virgilio with the near isogenic lines (NILs) of Taichung29*6/Virgilio using simple sequence repeat (SSR) method..Four near-isogenic lines of Taichung29*6/Virgilio and Taichung29 were inoculated with a stripe rust single-spore isolate of 2E16, that was same as the isolate used in NILs breeding process. Results indicated that Four Taichung29*6/Virgilio lines were resistant, and the recurrent cultivar Taichung29 was susceptible. The segregation ratio of the F₂ population is 3R: 1S and segregation ratio of BC₁ population is 1R: 1S based on the chi-squared (χ²) tests, which suggested that the stripe rust resistance in four NILs to 2E 16 was all controlled by a single dominant gene.YrVir1, one resistance genes in Virgilio, was linked to the resistance genes in T. Spelta album, so we selected 141 pairs of SSR primers on chromosome 2B to test the polymorphisms between NILs and their recurrent parent Taichung29. The results showed that specific dominant bands could be stably amplified by PCR with the primers Xgwm388, Xcfa2043, Xbarc349 and Xwmc332 between line N296 and Taichung29, and the specific bands were also amplified in the near genetic lines' resistance gene donor Virgilio; linkage detection proved that four SSR loci were all linked to resistance gene YrVir1 in N296, indicating that resistance gene YrVir1 originated from gene donor Virgilio, and the line N296 was named as Taichung29*61YrVir1. According to the allelic and molecular tests, YrVir1 was a new stripe rust resistance gene and we suggested it be designated Yr41.We tested 200 plants of Taichung29*6/YrVir1 F₂ population with primers Xgwm388, Xcfa2043, Xbarc349 and Xwmc332 respectively. Based on the analysis with software Mapmaker3.0b, the genetic distance to YrVir1 were 15.3cM, 12.0cM, 3.0cM and 12.4cM, respectively, and we supposed that the resistance gene YrVir1 was located at Xgwm388—Xcfa2043—YrVir1—Xbarc349—Xwmc332 on wheat chromosome 2BL in wheat SSR genetic map.The genomes of line N300, N304 and N312 were tested by the SSR primer Xbarc349, the results indicated that N296, N300, N304 and N312 was single-gene near isogenic lines containing YrVir1, and we designated them Taichung29*6/YrVir1. Xbarc349 was the SSR marker linked to stripe rust resistance gene YrVir1 in Virgilio.