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Key message: Powdery mildew resistance gene PmXNM, originated from the Chinese wheat landrace Xiaonanmai, was delimited to a 300.7-kb interval enriched with resistance genes. Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is a globally devastating disease threatening the yield and quality of wheat worldwide. The use of broad-spectrum disease resistance genes from wheat landraces is an effective strategy to prevent this pathogen. Chinese wheat landrace Xiaonanmai (XNM) was immune to 23 tested Bgt isolates at the seedling stage. The F1, F2, and F2:4 progenies derived from the cross between XNM and Chinese Spring (CS) were used in this study. Genetic analysis revealed that powdery mildew resistance in XNM was controlled by a single dominant gene, temporarily designated PmXNM. Bulked segregant analysis and molecular mapping delimited PmXNM to the distal terminal region of chromosome 4AL flanked by markers caps213923 and kasp511718. The region carrying the PmXNM locus was approximately 300.7 kb and contained nine high-confidence genes according to the reference genome sequence of CS. Five of these genes, annotated as disease resistance RPP13-like proteins 1, were clustered in the target region. Haplotype analysis using the candidate gene-specific markers indicated that the majority of 267 common wheat accessions (75.3%) exhibited extensive gene losses at the PmXNM locus, as confirmed by aligning the targeted genome sequences of CS with those of other sequenced wheat cultivars. Seven candidate gene-specific markers have proven effective for marker-assisted introgression of PmXNM into modern elite cultivars. [ABSTRACT FROM AUTHOR]

A sensitive and accurate chemiluminescence (CL) method was developed for one-step determination of diphenyl ether herbicides at trace level with nitrofen (2,4-dichlorophenyl-p-nitrophenyl ether) as a model analyte. Candida rugosa lipase (CRL) was immobilized on a nanocarrier of amine-linked covalent organic framework (named as COF-300-AR) through a self-assembly strategy. The formed nanocomposite of COF-300-AR@CRL owns dual enzymatic catalytic activities. It can directly catalyze luminol-dissolved oxygen reaction to produce an intense CL emission by virtue of oxidase mimic activity of COF-300-AR but also effectively decompose nitrofen to release phenolic compounds by the immobilized CRL. The released phenolic compounds own strong reducing capacity and in turn decrease the CL signal sharply. Under the optimal conditions, the decreased CL intensity presents a good linear response to nitrofen concentration in the 0.02–50.0 μM range. The limit of detection (LOD, 3sb/S) is 11 nM and the precision is 2.0% for replicate measurements of 50.0 nM nitrofen solution (n = 11). This method has the advantages of rapid analytical efficiency, good selectivity, satisfactory stability, and recyclability. Recovery experiments were conducted on spiked vegetable and fruit samples with the recoveries falling in the range 90.0–107.0%. [ABSTRACT FROM AUTHOR]

Key message: The powdery mildew resistance gene Pm58 was traced to a 141.3-kb interval with the co-segregating marker Xkasp68500 in wheat breeding. Pm58 is a powdery mildew resistance gene identified in Aegilops tauschii accession TA1662 and effective in a common wheat background. To finely map Pm58, an F2 population of 676 plants derived from the cross T093 × TA1662 was used for recombinant screening. We obtained 13 recombinants that occurred between the flanking markers Xhnu670 and Xhnu186. Genotyping and phenotyping these recombinant F2:3 families delimited Pm58 to a 0.22-cM interval (Xsts20220–Xkasp61553) on chromosome arm 2DS. The region carrying the Pm58 locus was approximately 141.3-kb, which contained eight annotated genes according to the reference genome sequence of Ae. tauschii AL8/78. Haplotype analysis of 178 Ae. tauschii accessions using the candidate gene-specific markers identified a disease resistance gene AET2Gv20068500 as a candidate for Pm58. Comparative mapping of the Pm58-containing interval revealed two presence/absence variations (PAVs) between AL8/78 and common wheat Chinese Spring. PAV-1 resides in the 3′-end of AET2Gv20068500. The majority of 158 common wheat cultivars (84.8%) displayed the absence of a 14.1-kb fragment in the PAV-1 region, which was confirmed by aligning the targeted genome sequences of the other sequenced Ae. tauschii accessions and common wheat cultivars. A co-segregating marker Xkasp68500 developed from AET2Gv20068500 can distinguish TA1662 from all randomly selected common wheat cultivars and will be instrumental for tracking Pm58 in breeding programs. [ABSTRACT FROM AUTHOR]

A chemiluminescence (CL) sensor was constructed for the one-step determination of glucose. Glucose oxidase (GOx) was successfully encapsulated into Zn-doped zeolitic imidazolate framework-67 (Zn–ZIF–67) via a simple one-pot strategy. The as-prepared GOx@Zn–ZIF–67 nanocomposite can trigger cascade reactions of glucose oxidation to generate H2O2 and H2O2-mediated luminol reaction to give an intense CL emission. The sensor responds linearly to glucose in the 20.0–400.0 μmol·L–1 range with a limit of detection (LOD) of 4.7 μmol·L–1. Eleven replicated measurements of 200.0 μmol·L–1 glucose solution gives a relative standard deviation (RSD) of 1.7%. The sensor exhibits good selectivity and stability and was successfully applied to the determination of glucose in real human serum samples. Schematic representation of one-step determination of serum glucose with GOx@Zn–ZIF–67 nanocomposite triggering cascade reactions between luminol and glucose. [ABSTRACT FROM AUTHOR]

HRP@ZIF–8 nanocomposite was prepared by in situ encapsulation of horseradish peroxidase (HRP) in the frame of zeolitic imidazolate framework–8 (ZIF–8) with a simple one-pot method. The HRP@ZIF–8 nanocomposite displays outstanding thermal stability and efficiently catalyzes the chemiluminescence (CL) reaction of luminol with hydrogen peroxide (H2O2) under near-neutral pH condition (pH 7–8). This CL system has a good response to H2O2 with a linear range of 0.1–100.0 μmol L−1. The limit of detection (LOD) is 0.06 μmol L−1 H2O2. By marriage with cholesterol oxidase, cholesterol is determined with a linear range from 0.1 to 100.0 μmol L−1 and a LOD of 0.04 μmol L−1. The relative standard deviations (RSD) are 1.7% and 2.5%, respectively, in 11 repeated measurements of 50.0 μmol L−1 solutions of H2O2 and cholesterol, indicating excellent precision of the method. The method shows good selectivity and has been applied to the determination of total cholesterol in real serum samples. No significant difference has been observed between the results obtained by this method and the cholesterol oxidase–peroxidase coupling method. [ABSTRACT FROM AUTHOR]