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Wheat stripe rust, caused by Puccinia striiformis Westend. f.sp. tritici Eriks (Pst), is one of the most important diseases of bread wheat worldwide. Breeding resistant wheat cultivars is the most economical, effective and environmentally friendly way for controlling wheat stripe rust in China. The Romanian wheat line Fundulea 900 showed good resistance to wheat stripe rust at the adult stage. The present study aimed to map the quantitative trait loci (QTLs) for stripe rust resistance in 176 F2:6 recombinant inbred lines (RIL) derived from the cross of Fundulea 900 × Thatcher. The RIL population was phenotyped for stripe rust (YR) severity at Mianyang in the Sichuan province and Baoding in the Hebei province in the 2016/2017 and 2017/2018 cropping seasons. SSR markers combined with a preferred screened group (PSG) analysis were used to identify the QTLs for stripe rust in the population. Three QTLs for stripe rust resistance were mapped on chromosomes 1AL, 7BL and 7DS, respectively. All three QTLs originated from Fundulea 900 and were detected in all the environments. The QTL on 7DS was provided by the known resistance gene Yr18/Lr34. The two QTLs on chromosomes 1AL and 7BL were explained by 9.2 to 21.5% and 5.1 to 10.1% of the phenotypic variance, respectively and might be new QTLs. The QTLs identified in the study and their closely linked markers can be used for marker-assisted selection (MAS) in wheat breeding programmes.

Common wheat (Triticum aestivum L.) is the major crop cultivated in Xinjiang and Anhui provinces of China. The climate in these two provinces is favourable for wheat leaf rust (Puccinia triticina) (Pt) infection. Here, we demonstrate a detailed investigation on the leaf rust resistance of 60 major wheat cultivars cultivated in these two regions. A mixture of high virulent Pt races (THTT, THTS, THTQ and PHPS) were used to phenotype all the collected wheat cultivars at an adult plant stage. Phenotypic disease severity (FDS) and the area under the disease progress curve (AUDPC) for each of these wheat cultivars were calculated. Among all the tested wheat cultivars, three cultivars (Xindong20, Xindong 29 and 99AR142-1) with the lowest FDS and AUDPC may carry major resistance genes. Twenty-seven cultivars (45% of the total tested ones) showed a relatively lower resistance with an average of 12.52% FDS and 126.3 AUDPC. Minor resistance or slow rusting genes may be present in this group of cultivars. Molecular markers for leaf rust resistance genes Lr1, Lr9, Lr19, Lr24, Lr26 and Lr34 were further used for the genotypic screening. Lr1, Lr19, Lr26 and Lr34 were detected in 19 (31.7%), 1 (1.7%), 12 (20%) and 6 (10%) wheat cultivars, respectively. Neither Lr9 nor Lr24 could be detected in any of the tested cultivars. These results will greatly improve wheat molecular breeding for leaf rust resistance in these areas.

The wheat (Triticum aestivum L.) line 19HRWSN-129 from CIMMYT showed resistance to the major Puccinia triticina (Pt) races collected in China. A 144 F2:3 population was generated by crossing the resistant line 19HRWSN-129 with the susceptible line Zhengzhou5389. All the F2:3 plants were phenotyped by inoculating with the Pt race PHGN in the greenhouse. Segregation analysis indicated the presence of a single dominant gene conferring resistance to leaf rust in the wheat line 19HRWSN-129, temporarily designated as Lrshi. Using molecular markers, we mapped this resistance locus on chromosome 7BL. It was closely linked to the SSR markers Xgwm344 and Xcfa2040 with genetic distances of 2.8 cM and 1.4 cM, respectively. Compared with other chromosome 7BL-located leaf rust resistance genes (Lr14a, Lr14b, Lr68), we demonstrate, that Lrshi is a novel wheat leaf rust resistance gene.

The wheat cultivar Weimai 8 is a good source of adult-plant resistance to leaf rust in China. In order to understand the genetic background of the resistance genes, 179 F2:3 families derived from the cross Weimai 8 and Zhengzhou 5389 (susceptible to leaf rust) were used to construct a linkage map. Results showed that there was a major QTL on chromosome 2AS, temporarily named QLr.hbau-2AS, responsible for the resistance. QLr.hbau-2AS from the resistant parent Weimai 8 was between the SSR markers Xcfd36 and Xbarc1138, with an interval length of 2.58 cM. In the 2010-2011, 2011-2012 and 2012-2013 crop seasons, it explained 25.79, 71.55 and 60.72% of the phenotypic variation, respectively. The location of QLr.hbau-2AS was close to the leaf rust resistance gene Lr37. However, they may not be the same since QLr.hbau-2AS has a different virulence test response from Lr37. This study identified two closely linked flanking molecular markers QLr.hbau-2AS and these molecular markers will help marker-assisted selection in breeding resistant cultivars in the future.

Leaf rust (LR), caused by Puccinia triticina (Pt), is worldwide one of the most spread diseases in common wheat (Triticum aestivum L.). With the objective of identifying and mapping new genes for resistance to leaf rust, F1 and F2 plants from a cross between the resistant cultivar LB0288 and the susceptible cultivar Thatcher were inoculated with the Chinese P. triticina pathotype THTT in the greenhouse. A set of 1273 simple sequence repeat (SSR) primer pairs were used to test the parents and the resistant and susceptible bulks. The results indicated, that LB0288 carried a single dominant resistance gene LrLB88, closely linked to the CAPS marker of Lr1 (WR003) and the SSR marker Xbarc144, with genetic distances of 0 cM and 5.3 cM, respectively. Based on the chromosomal location and seedling reactions, it can be concluded that LrLB88 might be a new leaf rust resistance gene. These markers can be useful for marker assisted selection in breeding of leaf rust resistant wheat cultivars.

The wheat (Triticum aestivum L.) line 5R618, bred at the China Agricultural University, is resistant in the seedling stage to the majority of the current Chinese pathotypes of wheat leaf rust (Puccinia triticina). To identify and map the leaf rust resistance gene in the 5R618 line, F2 plants and F2:3 families from a cross between 5R618 and Zhengzhou5389 (susceptible) were inoculated in the greenhouse with the Chinese P. triticina pathotype THJP. Results from the F2 and F2:3 populations indicate that a single dominant gene, temporarily designated Lr5R, conferred resistance. Using the molecular marker method, Lr5R was located on the 3DL chromosome. It was closely linked to the markers Xbarc71 and OPJ-09 with genetic distances of 0.9 cM and 1.0 cM, respectively. At present only one designated gene (Lr24) is located on the 3DL chromosome. The genetic distance between Lr5R and Lr24 confirms that Lr5R is a new leaf rust resistance gene.