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The increasing severity and prevalence of powdery mildew aided by extensive use of semi-dwarf cultivars and high levels of nitrogenous fertilizers are causing significant yield losses in wheat. Resistant cultivars are the most cost-effective and environmentally friendly approach to manage the disease. The objective of this study was to identify quantitative trait loci (QTL) for powdery mildew resistance in a doubled haploid (DH) population from a cross between leading Chinese cultivars, Yangmai 16 and Zhongmai 895. A high-density genetic map comprising of 14,480 non-redundant markers (equal to 148,179 SNPs) in 21 wheat chromosomes was constructed by genotyping the population with the Wheat 660 K SNP array. The DH population was phenotyped for powdery mildew resistance at the adult plant stage in multiple field trials, including four environments in the 2016–2017 cropping season and two environments in 2017–2018. Composite interval mapping detected six stable QTL explaining 3.8–23.6% of the phenotypic variance across environments. QPmyz.caas-5DS, QPmyz.caas-6BL and QPmyz.caas-7BS, are probably new QTL for powdery mildew resistance. One SNP marker closely linked to QPmyz.caas-6BL, the most stable QTL, was converted into a Kompetitive Allele-Specific PCR marker (K_AX-94973433) and validated on 103 commercial wheat cultivars. Significantly lower maximum disease severities of cultivars with the resistance-associated allele than those with the susceptibility-associated allele at QPmyz.caas-6BL in some environments indicated partial effectiveness of the marker. The novel QTL and their closely linked markers identified in the present study should facilitate development of cultivars with improved powdery mildew resistance.

Fusarium head blight (FHB), also known as head scab, is a devastating fungal disease of bread and durum wheat worldwide. It reduces yield, lowers seed germination, reduces grain quality, and renders grain unsuitable for human or animal consumption due to mycotoxin contamination. Use of host resistance in commercially cultivated wheat varieties is an economical, effective and environmentally friendly method to manage FHB. In order to map loci underlying FHB resistance in synthetic-derived bread wheat line SYN1, a doubled haploid (DH) population of 169 lines was developed through hybridizing SYN1 with FHB-susceptible line Ocoroni. The DH population was evaluated in spray-inoculated field nurseries in the 2010 and 2011 cropping seasons at the El Batan Experiment Station of the International Maize and Wheat Improvement Center, Mexico. Ten marked spikes from each plot were scored for disease response and an FHB index was subsequently calculated. The population was genotyped with 1391 genotyping by sequencing and 106 simple-sequence repeat (SSR) loci and 28 linkage groups were constructed. These linkage groups were anchored by SSRs to all chromosomes, except 4D, 5D and 6D. Using the inclusive composite interval mapping algorithm, three genomic regions were associated with FHB resistance, including a major QTL on chromosome 2D accounting for 25 % of the phenotypic variation explained (PVE) and two minor QTLs on chromosomes 1B (4.7 % PVE) and 7A (4.2 % PVE), with all favorable alleles contributed by SYN1. The average FHB index of lines with all three SYN1 alleles was substantially lower (61.4 %) than that of those with Ocoroni alleles.

Spot blotch, caused by Cochliobolus sativus, is an important foliar disease of wheat in warmer wheat-growing regions leading to significant reductions in grain yield and quality. Although inoculum levels can be reduced by planting disease-free seed, treatment of plants with fungicides and crop rotation, genetic resistance is likely to be a robust, economical and environmentally friendly tool in the control of spot blotch. The spot blotch resistant synthetic derivative ‘SYN1’ was developed from a cross between two resistance sources, Mayoor and the primary synthetic bread wheat Tksn1081/Ae. squarrosa (222) that are likely to form an important component of resistance in many elite CIMMYT bread wheats. In order to map the loci underlying the resistance of ‘SYN1’, a doubled-haploid population produced from a cross between ‘SYN1’ and the susceptible CIMMYT-derived variety Ocoroni-86 was evaluated in artificially inoculated field nurseries in the 2010–2011 and 2011–2012 crop seasons at CIMMYT’s research station in Agua Fria, Mexico. Disease assessment was performed on three or four occasions and subsequently area under disease progress curve (AUDPC) calculated. Genotyping was with genotyping by sequencing and simple sequence repeat markers. Using inclusive composite interval mapping, three genomic regions were found to have a significant effect on spot blotch AUDPC in each of the 2 years of trials with phenotypic variation explained by QSb.cim-1B of 8.5 %, 17.6 % by QSb.cim-3B and 12.3 % by QSb.cim-5A. The quantitative trait loci (QTL) mapping results showed that the favorable alleles of QSb.cim-1B, QSb.cim-3B and QSb.cim-5A were derived from the synthetic-derived bread wheat SYN1. Genotypes of the parents of SYN1 indicated that the favorable alleles at these three QTLs were all inherited from Mayoor.

An improved thermal decomposition method was used to directly prepare water-soluble Fe3O4 magnetic nanoparticles (MNPs) with relatively higher quality via reductive decomposition of ferric acetylacetonate [Fe(acac)3], in the presence of benzyl ether and phenol, in which inexpensive phenol acted as reducing agent and stabilizer, produce the semi phenol-benzoquinone coated on the Fe3O4 and make the Fe3O4·MNPs water-soluble and the colloidal solution stable. By changing the molar ratio of phenol to Fe(acac)3 and reaction time, the size of Fe3O4·MNPs could be varied from 19.3 ± 4.4 nm to 9.7 ± 1.5 nm, with the saturation magnetizations in the range of 51.3–62.9 emu/g.