Publications by authors named "D McLaren"

550 Publications

Molecular assessment of pathotype diversity of Phytophthora sojae in Canada highlights declining sources of resistance in soybean.

Plant Dis 2021 Jun 23. Epub 2021 Jun 23.

Université Laval, Phytologie, 2425 rue de l'Agriculture, Pavillon Comtois, Québec, Quebec, Canada, G1V0A6;

The large-scale deployment of Rps (resistance to Phytophthora sojae) genes in soybean has led to the rapid evolution of the virulence profile (pathotype) of P. sojae populations. Determining the pathotypes of P. sojae isolates is important in selecting soybean germplasm carrying the proper Rps, but this process is fastidious and requires specific expertise. In this work, we used a recently developed molecular assay to assess the pathotypes of P. sojae isolates obtained throughout the provinces of Québec, Ontario and Manitoba. In preliminary assays, the molecular tool showed equivalent prediction of the pathotypes as a phenotyping assay and proved to be much faster to apply while eliminating intermediate values. Following the analysis of nearly 300 isolates, 24 different pathotypes were detected in Québec and Ontario, compared to only eight in Manitoba, where soybean culture is more recent. Pathotype 1a, 1c, 1d was predominant in Québec, while 1a, 1b, 1c, 1d, 1k was the most common in Manitoba. Overall, the results showed that 98 and 86% of the isolates carried pathotype 1a or 1c, respectively, suggesting that Rps1a and Rps1c were no longer effective in Canada. Based on the history of soybean varieties used in surveyed fields, it was found that 84% of them contained Rps genes that were no longer resistant against the pathotypes of the isolates found in the fields. While highlighting an easier and more precise option to assess pathotypes, this study presents the first pan-Canadian survey of P. sojae and stresses the importance of carefully managing the declining sources of resistance.
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http://dx.doi.org/10.1094/PDIS-04-21-0762-REDOI Listing
June 2021

Mapping QTL associated with partial resistance to Aphanomyces root rot in pea (Pisum sativum L.) using a 13.2 K SNP array and SSR markers.

Theor Appl Genet 2021 Jun 15. Epub 2021 Jun 15.

Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, T6G 2P5, Canada.

Key Message: A stable and major QTL, which mapped to an approximately 20.0 cM region on pea chromosome 4, was identified as the most consistent region conferring partial resistance to Aphanomyces euteiches. Aphanomyces root rot (ARR), caused by Aphanomyces euteiches Drechs., is a destructive soilborne disease of field pea (Pisum Sativum L.). No completely resistant pea germplasm is available, and current ARR management strategies rely on partial resistance and fungicidal seed treatments. In this study, an F recombinant inbred line population of 135 individuals from the cross 'Reward' (susceptible) × '00-2067' (tolerant) was evaluated for reaction to ARR under greenhouse conditions with the A. euteiches isolate Ae-MDCR1 and over 2 years in a field nursery in Morden, Manitoba. Root rot severity, foliar weight, plant vigor and height were used as estimates of tolerance to ARR. Genotyping was conducted with a 13.2 K single-nucleotide polymorphism (SNP) array and 222 simple sequence repeat (SSR) markers. Statistical analyses of the phenotypic data indicated significant (P < 0.001) genotypic effects and significant G × E interactions (P < 0.05) in all experiments. After filtering, 3050 (23.1%) of the SNP and 30 (13.5%) of the SSR markers were retained for linkage analysis, which distributed 2999 (2978 SNP + 21 SSR) of the markers onto nine linkage groups representing the seven chromosomes of pea. Mapping of quantitative trait loci (QTL) identified 8 major-effect (R > 20%), 13 moderate-effect (10% < R < 20%) effect and 6 minor-effect (R < 10%) QTL. A genomic region on chromosome 4, delimited by the SNP markers PsCam037549_22628_1642 and PsCam026054_14999_2864, was identified as the most consistent region responsible for partial resistance to A. euteiches isolate Ae-MDCR1. Other genomic regions important for resistance were of the order chromosome 5, 6 and 7.
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http://dx.doi.org/10.1007/s00122-021-03871-6DOI Listing
June 2021

The risks of solar geoengineering research.

Science 2021 Jun;372(6547):1161

Environmental Studies, Mount Holyoke College, South Hadley, MA 01075, USA.

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http://dx.doi.org/10.1126/science.abj3679DOI Listing
June 2021

Direct Analysis from Phase-Separated Liquid Samples using ADE-OPI-MS: Applicability to High-Throughput Screening for Inhibitors of Diacylglycerol Acyltransferase 2.

Anal Chem 2021 04 5;93(15):6071-6079. Epub 2021 Apr 5.

Merck & Company, Incorporated, 2000 Galloping Hill Road, Kenilworth, New Jersey 07033, United States.

The primary goal of high-throughput screening (HTS) is to rapidly survey a broad collection of compounds, numbering from tens of thousands to millions of members, and identify those that modulate the activity of a therapeutic target of interest. For nearly two decades, mass spectrometry has been used as a label-free, direct-detection method for HTS and is widely acknowledged as being less susceptible to interferences than traditional optical techniques. Despite these advantages, the throughput of conventional MS-based platforms like RapidFire or parallel LC-MS, which typically acquire data at speeds of 6-30 s/sample, can still be limiting for large HTS campaigns. To overcome this bottleneck, the field has recently turned to chromatography-free approaches including MALDI-TOF-MS and acoustic droplet ejection-MS, both of which are capable of throughputs of 1 sample/second or faster. In keeping with these advances, we report here on our own characterization of an acoustic droplet ejection, open port interface (ADE-OPI)-MS system as a platform for HTS using the membrane-associated, lipid metabolizing enzyme diacylglycerol acyltransferase 2 (DGAT2) as a model system. We demonstrate for the first time that the platform is capable of ejecting droplets from phase-separated samples, allowing direct coupling of liquid-liquid extraction with OPI-MS analysis. By applying the platform to screen a 6400-member library, we further demonstrate that the ADE-OPI-MS assay is suitable for HTS and also performs comparably to LC-MS, but with an efficiency gain of >20-fold.
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http://dx.doi.org/10.1021/acs.analchem.0c04312DOI Listing
April 2021