The occurrence of malondialdehyde (MDA), a secondary end product of the oxidation of polyunsaturated fatty acids, is considered a useful index of general lipid peroxidation. A common method for measuring MDA, referred to as the thiobarbituric acid-reactivesubstances (TBARS) assay, is to react it with thiobarbituric acid (TBA) and record the absorbance at 532 nm. However, many plants contain interfering compounds that also absorb at 532 nm, leading to overestimation of MDA values. Extracts of plant tissues including purple eggplant (Solanum melongena L.) fruit, carrot (Daucus carota L.) roots, and spinach (Spinacia oleracea L.) leaves were assessed for the presence of MDA and other non-MDA compounds absorbing at 532 nm. A method described herein corrects for these interferences by subtracting the absorbance at 532 nm of a solution containing plant extract incubated without TBA from an identical solution containing TBA. The reliability and eciency of this spectrophotometric method was assessed by altering the relative ratios of exogenous MDA additions and/or extracts of red cabbage (Brassica oleracea L.) leaves containing interfering compounds and then measuring MDA recovery. Reliability was also validated through high-performance liquid chromatography and high-performance liquid chromatography-mass spectrometry techniques. Results indicated that over 90% of exogenously added MDA could be recovered through the improved protocol. If there were no corrections for interfering compounds, MDA equivalents were overestimated by up to 96.5%. Interfering compounds were not detected in vegetables such as lettuce (Lactuca sativa L.) and spinach which had low or negligible concentrations of anthocyanidin derivatives. Comparisons between the TBARS method presented here and two currently accepted protocols indicated that the new modi®ed method exhibits greater accuracy for quantifying TBA-MDA levels in tissues containing anthocyanins and/or other interfering compounds. This modi®ed protocol represents a facile and rapid method for assessment of lipid peroxidation in virtually all plant species that contain interfering compounds.

Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. Questions? Contact the NRC Publications Archive team atPublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information. NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. NRC Publications Record / Notice d'Archives des publications de CNRC:http://nparc.cisti-icist.nrc-cnrc.gc.ca/eng/view/object/?id=7ee3580f-c134-4185-a6d3-cb87c5e10071 http://nparc.cisti-icist.nrc-cnrc.gc.ca/fra/voir/objet/?id=7ee3580f-c134-4185-a6d3-cb87c5e10071 The ferrous oxidation-xylenol orange (FOX) assay was adapted for quantifying lipid hydroperoxides (LOOHs) in plant extracts. Excised pieces of several fruit and vegetable species were exposed to 83 kJ m -2 day -1 of biologically effective ultraviolet B irradiance (UV-B BE ) for 10-12 days to induce cellular oxidation. The LOOH and thiobarbituric acid reactive substance (TBARS) concentrations of these plant tissues were assessed with the FOX and iodometric assays for the former and a modified TBARS assay for the latter. There was generally good agreement between the FOX and iodometric methods both prior to and following the UV exposure. However, the iodometric assay appeared to have some difficulty in consistently quantifying lower LOOH levels (<11 µM), whereas the FOX assay measured LOOH concentrations as low as 5 µM. All tissues exhibited UV-induced increases in TBARS, indicating a marked degree of cellular oxidation in the exposed tissue segments. Compared with the iodometric assay, the FOX method consistently generated less variable LOOH values. The presence of authentic linoleic acid-OOHs in spiked avocado and spinach samples (11 µM) was identified with liquid chromatography-mass spectrometry techniques, which validated corresponding FOX assay results. The FOX method is inexpensive, is not sensitive to ambient O 2 or light levels, and can rapidly generate LOOH measurements. The physiological value of the FOX assay resides in its ability to measure initial rather than more advanced fatty acid oxidation; hence, early membrane-associated stress events in plant tissue can be detected.

The apple (Malus × domestica Borkh.) is an economically and culturally important crop grown worldwide. Growers of this long-lived perennial must produce fruit of adequate quality while also combatting abiotic and biotic stress. Traditional apple breeding can take up to 20 yr from initial cross to commercial release, but genomics-assisted breeding can help accelerate this process. To advance genomics-assisted breeding in apple, we performed genome-wide association studies (GWAS) and genomic prediction in a collection of 172 apple accessions by linking over 55,000 single nucleotide polymorphisms (SNPs) with 10 phenotypes collected over 2 yr. Genomewide association studies revealed several known loci for skin color, harvest date and firmness at harvest. Several significant GWAS associations were detected for resistance to a major fungal pathogen, apple scab (Venturia ineaqualis [Cke.] Wint.), but we demonstrate that these hits likely represent a single ancestral source. Using genomic prediction, we show that most phenotypes are sufficiently predictable using genome-wide SNPs to be candidates for genomic selection. Finally, we detect a signal for firmness retention after storage on chromosome 10 and show that it may not stem from variation in PG1, a gene repeatedly identified in bi-parental mapping studies and widely believed to underlie a major QTL for firmness on chromosome 10. We provide evidence that this major QTL is more likely due to variation in a neighboring ethylene response factor (ERF) gene. The present study showcases the superior mapping resolution of GWAS compared to bi-parental linkage mapping by identifying a novel candidate gene underlying a well-studied, major QTL involved in apple firmness.