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Identification and mapping new powdery mildew resistance (Pm) genes is important for resistance breeding in wheat. Common wheat (Triticum aestivum L.) line X3986-2 was tested against 27 isolates of Blumeria graminis f. sp. tritici. To identify the Pm gene(s) in X3986-2, an F2 population and its derived F2:3 lines were developed from a cross between X3986-2 and susceptible line Mingxian169. Segregation ratios indicated the presence of a single dominant Pm locus, tentatively designated PmX3986-2. Bulked segregant analysis was applied to screen for molecular markers linked to PmX3986-2. Two sequence characterized amplified region (SCAR) markers SCAR112 and SCAR203, and five simple sequence repeat markers CFD40, CFD78, CFD81, GWM293 and WMC443 on chromosome 5D were linked to PmX3986-2, with CFD81 and SCAR112 flanking PmX3986-2 at 0.6 and 1.5 cM, respectively. This suggests that PmX3986-2 may be a novel allele of loci Pm2, Pm46 and PmLX66 on chromosome arm 5DS. PmX3986-2 with its tightly linked DNA markers should be useful for broadening the genetic basis of Pm and rapidly transferring the resistance gene to susceptible cultivars or for us in gene pyramiding for resistance breeding.

Stripe rust resistance gene YrC591, present in wheat cultivar C591, is effective against currently important Puccinia striiformis Westend. f. sp. tritici isolates in China. An F2:3 population (127 lines) was developed by crossing C591 with susceptible cultivar Taichung 29. Thirty four simple sequence repeat (SSR) and 155 sequence tagged site (STS) markers located on chromosome 7BL were used to perform bulk segregant analysis. Eight SSR markers, cfa2040, wmc273, wmc166, gwm984, barc32 wmc276, barc182 and gwm146, and 6 STS markers, mag1714, mag1757, mag1811, BE425120, BE471173 and BG607810, were polymorphic between the parents and contrasting resistant and susceptible DNA pools. F2:3 lines were genotyped with these polymorphic markers. Linkage analysis indicated that YrC591 was flanked by Xmag1714 and Xbarc182 with genetic distances of 1.2 and 0.4 cM, respectively. In addition, validation of the SSR markers cfa2040, wmc273 and barc32, and STS markers mag1714 and BE425120 was carried out using wheat lines with C591 as a parent, indicating that these markers should be effective in tracing this gene in marker-assisted selection.

Quantitative trait loci (QTLs) with additive (a), additive × additive (aa) epistatic effects, and their treatmental interactions (at and aat) were studied under salt stress and normal conditions at seedling stage of wheat (Triticum aestivum L.). A set of 182 recombinant inbred lines (RILs) derived from cross Xiaoyan 54 × Jing 411 were used. A total of 29 additive QTLs and 17 epistasis were detected for 12 traits examined, among which eight and seven, respectively, were identified to have QTL × treatment effects. Physiological traits rather than biomass traits were more likely to be involved in QTL × treatment interactions. Ten intervals on chromosomes 1A, 1D, 2A (two), 2D, 3B, 4B, 5A, 5B and 7D showed overlapping QTLs for different traits; some of them represent a single locus affecting different traits and/or the same trait under both treatments. Eleven pairs of QTLs were detected on seemingly homoeologous positions of six chromosome groups of wheat, showing synteny among the A, B and D genomes. Ten pairs were detected in which each pair was contributed by the same parent, indicating a strong genetic plasticity of the QTLs. The results are helpful for understanding the genetic basis of salt tolerance in wheat and provide useful information for genetic improvement of salt tolerance in wheat by marker-assisted selection.