Postulation of Seedlings Resistance Genes to Yellow Rust in Commercial Wheat Cultivars from Yunnan Province in China

The objective of this study was to characterize yellow （stripe） rust resistance gene（s） in 52 commercial wheat cultivars from Yunnan Province in China, and to provide information for their rational deployment in field. Seedlings of wheat cultivars were inoculated with 25 differential isolates ofPuccinia striiformis from foreign and home to postulate resistance genes to yellow rust, and then validated by pedigree. There were 10 probable resistance genes characterized in these cultivars, in which, Yr9 was most commonly postulated to be present in thirteen cultivars. Yr21, the second, was present in four cultivars. Yr8, the third, were present in three cultivars. Yr6, Yrl 7 and Yr26, the fourth, was present in two cultivars respectively. The other gene（s） such as, Yr2＋YrA, Yr7 and Yr27, were only present in single cultivar（s）; unknown gene（s） or gene（s） combination（s） were present in 22 cultivars. One cultivar （Yunmai 42） had no resistance gene tested in this study. Cultivars such as Yunmai 52, Mian 1971-98, Kunmai 4, and Yunmai 56 carried effective genes and can be popularized mainly; Yr9 should be planted with other Yr genes. In the meantime other effective genes should be introduced to realize gene diversity for controlling wheat yellow rust. Yunmai 42 should be reduced to avoid rust breakout. Unknown gene cultivars should be utilized and be researched deeply.

Postulation of seedling leaf rust resistance genes in 84 Chinese winter wheat cultivars

Wheat leaf rust（caused by Puccinia triticina） is one of the most important fungal diseases in China. There are tens of winter wheat cultivars which are approved to be released by the government at a national level and more than 100 wheat cultivars at the provincial level. But there is no information about leaf rust（Lr） genes in these cultivars, which makes it difficult for farmers and breeders to select which cultivars they should plant in their fields and use in their breeding programs. The objective of this paper was to identify the leaf rust resistant genes at seedling stage present in the 84 commercial wheat cultivars from China that have been released in the past few years. A set of 20 near isogenic lines with Thatcher background and 6 lines with known Lr genes were used to test the virulence of 12 races of P. triticina（Pt）. By comparing the infection types（ITs） produced on the 84 cultivars by the 12 Pt races with the ITs on the differential sets, the Lr genes were postulated. In addition, 8 molecular markers of Lr genes such as Lr9, Lr10, Lr19, Lr20, Lr21, Lr24, Lr26 and Lr29, which are closely linked to or co-segregated with the Lr gene, were used for further validation of the genes in the 84 Chinese winter wheat cultivars. Twelve Lr genes, including Lr1, Lr3,（Lr3bg）,（Lr3ka）, Lr11, Lr13, Lr14 a, Lr16, Lr26, Lr27, Lr30 and Lr31 were postulated to be present either singly or in combinations in these Chinese wheat cultivars. Lr3 and Lr26 were detected most often in the tested cultivars, with frequencies of 51.2 and 38.1%, respectively. No wheat Lr genes were detected in 16 cultivars, and 4 cultivars may carry unknown Lr genes other than those used in this study. Lr9, Lr20, Lr21, Lr24, Lr25 and Lr29 were not present in any of the 84 tested accessions.

Postulation of Seedling Resistance Genes in 20 Wheat Cultivars to Yellow Rust (Puccinia striiformis f. sp. tritici)

The gene postulation, cluster analysis and pedigree analysis of 20 wheat cultivars to 28 physiological races of yellow rust （Puccinia striiformis） were conducted under greenhouse conditions, The spectrum of their resistance were compared each other. None of the 20 cultivars were resistant to all the test pathogens. The cultivars containing resistance genes Yr5 and Yr24 were not find and genes Yr8, Yrl9 and Yr27 could not be postulated from cultivars tested due to the susceptibility to all isolates used. A total of 6 probale seedling yellow rust resistance genes or gene combinations （Yrl, Yr2, Yr2 ＋ YrHVII, Yr3 ＋ unknown, Yr3 ＋ Yr4, YrAlba） were postulated in the wheat cultivars （Atou, Flanders, Maris Huntsman, Bouquet, Holdfast, Elite Lepeuple, and Vilmorin 27）. The gene combination Yr2＋YrHVII with the highest frequency （35%） was present in 7 cultivars. The Yr genes present in some wheat cultivars could not be postulated because of non-matching virulence combinations with any of known genes. Cluster result showed that Yr2 and Yr3 are the most important genes in the cultivars. The 13 cultivars are believed to have the pedigree of Noe, which was selected from South Russian wheat. These results will be useful for wheat breeding and provide information about genetic control of wheat yellow rust.

Postulation of Leaf Rust Resistance Genes in Seven Chinese Spring Wheat Cultivars

To detect the leaf rust resistance genes in the 7 Chinese spring wheat clultivars Shenmian 99025, Shenmia 99042, Shenmian 85, Shenmian 91, Shenmian 96, Shenmian 1167 and Shenmian 962, Thatcher, Thatcher backgrounded near-isogenic lines and 15 pathotypes of P. triticina were used for gene postulate at the seedling stage, and 9 of the 15 pathotypes were used in the field tests. Molecular markers closely linked to, or co-segregated with resistance genes Lrl, Lr9, LrlO, Lrl9, Lr20, Lr21, Lr24, Lr26, Lr28, Lr29, Lr32, Lr34, Lr35, Lr37, Lr38, and Lr47 were screened to assist detection of the resistance genes. As results, 4 known resistance genes, including Lrl, Lr9, Lr26, and Lr34, and other unknown resistance genes were postulated singly or in combination in the tested cultivars. Shenmian 85, Shenmian 91, Shenmian 96, Shenmian 962, Shenmian 1167, and Shenmian 99042 are potentially useful for wheat production and breeding programs. The result suggested that combining gene postulation, molecular markers and pedigrees is effective and more accuracy method to know the resistance genes in cultivars.

Characterization and Molecular Mapping of a Stripe Rust Resistance Gene in Synthetic Wheat CI110

Stripe rust,caused by Puccinia striiformis f.sp.tritici（Pst）,is one of the most destructive diseases of wheat（Triticum aestivum L.）.To diversify stripe rust-resistant resources for wheat breeding programs,a CIMMYT synthetic wheat line CI110 was identified to be resistant to 28 isolates of Pst,including 6 Chinese prevalent races CYR28-CYR33.Genetic analysis indicated that a single dominant gene was responsible for the stripe rust resistance in CI110,temporarily designated YrC110.A molecular map,harboring YrC110 and 9 linked SSR markers,was constructed through simple sequence repeat（SSR）,and bulked segregant analysis.These linked markers and YrC110 were assigned on the short arm of chromosome 1B using the Chinese Spring nullisomic-tetrasomic and ditelosomic stocks.Gene postulation based on seedling reaction patterns to 30 Pst isolates suggested that the resistance gene YrC110 seemed different from the other known resistance genes tested,such as Yr9,Yr10,Yr15,Yr24,and Yr26/YrCH42.Four SSR markers Xbarc187150,Xgwm18227,Xgwm11223,and Xbarc240292 distinguished YrC110 from Yr10,Yr15,Yr24,and Yr26/YrCH42,and could be used as diagnostic ones for YrC110 in wheat resistant breeding programs against stripe rust.

Identification of leaf rust resistance genes in common wheat varieties from China and foreign countries

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.