Marie Thérèse Charles

Effect of hyperbaric treatments on the quality attributes of tomato

Goyette, B., Vigneault, C., Charles, M. T. and Raghavan, V. G. S. 2012. Effect of hyperbaric treatments on the quality attributes of tomato. Can. J. Plant Sci. 92: 541–551. An experimental hyperbaric system was conceptualized, designed and built to explore the effect of hyperbaric treatment on the quality attributes of tomato. Tomato fruits at the early breaker stage were subjected to hyperbaric pressures of 1, 3, 5, 7 or 9 atmabs for different durations (5, 10 or 15 d) at 13°C. The effect of hyperbaric treatment on postharvest quality of tomato fruit was evaluated with an emphasis on weight loss, firmness, color, titratable acidity (TA) and total soluble solids (TSS). Hyperbaric treated tomato fruit ripened more slowly and were characterized by lower respiration rate than fruits kept under ambient conditions. Significant differences in weight loss, color, lycopene concentration and firmness were found between hyperbaric treated and control tomato fruit. No significant difference was found in the sugar/acid ratio (TSS/TA).

Phenolic Composition and Antioxidant Capacity of Newly Developed Strawberry Lines from British Columbia and Quebec

The total phenolic composition (TPC) and the total antioxidant capacity (TAC) of eleven strawberry genotypes selected from the AAFC breeding program (BC2-72-17, BC2-90-43, BC96-33-4 and BC98-49-34 from British Columbia; and APF937-1, APF939-71, LL981-24, LL9819-14, LL982-14, LL0220-10 and SJ9332-7 from Quebec) were evaluated using high-performance liquid chromatography (HPLC) and ferric reducing/antioxidant power (FRAP) assays. TPC and TAC values of these genotypes were compared to those of four commercially grown cultivars (‘Chambly,’ ‘Kent,’ ‘Veestar’ and ‘Yamaska’) and the effects on fruit quality and shelf life were studied. Several groups of phenolic compounds, including anthocyanins, flavonols, hydroxycinnamic, ellagic and benzoic acids, were identified and quantified by HPLC. Significant variation of TPC was observed between genotypes, and anthocyanins were found to be the predominant phenolic group, contributing to 79.2% of the TPC. A significant correlation (r = 0.96) was observed between TPC and anthocyanin content. BC2-72-17 had the highest anthocyanin content and differed significantly from the other genotypes. Although the highest TPC (2123.8 μg g−1) was found in BC2-72-17, this genotype did not have the highest antioxidant capacity. The highest TAC (2259.0 μg g−1) was found in BC2-90-43, indicating that other phenolics may have made a greater contribution than anthocyanins to the high TAC. At room temperature, LL0220-10, SJ9332-7 and ‘Yamaska’ had a three-day shelf life, while it was only two days for all other genotypes. There was a negative correlation between shelf life and ellagic acids, flavonol and anthocyanin levels but this relationship was not significant (p > 0.0.). The fruit soluble solids content (SSC) and titratable acidity (TA) varied between genotypes. ‘Veestar’ and LL981-24 had the highest SSC (7.5). These results point to the importance of identifying genotypes with high phenolic monomer activities in screening for lines with high TAC, to ensure their use in breeding programs aimed at improving the nutritional value of strawberry.

In vitro antifungal activity and mode of action of selected polyphenolic antioxidants on Botrytis cinerea

Six selected antioxidants (catechin, quercetin-3-galactoside, cyanidin-3-glucoside, pelargonidin-3-glucoside, ellagic and gallic acids) were evaluated in vitro for their antifungal activities and mode of action on Botrytis cinerea Pers., one of the most important pathogens of strawberries. Inhibitory effects were found for all the tested antioxidants, but varied at different fungal developmental stages. Catechin and quercetin-3-galactoside showed linear inhibitory effects on germ tube elongation, with the highest suppression ratios of 54.8% and 58.8% respectively. No significant effect was found on spore germination between treatments and control. Gallic acid showed very strong and linear inhibition on spore germination (r = −0.95), but the effect diminished after spore germination. Cyanidin-3-glucoside and pelargonidin-3-glucoside provided effective control on the fungi as concentrations increased. The arresting effect of ellagic acid on development of B. cinerea was quadratic. Ellagic acid inhibited germ tube elongation and mycelial growth at its highest and lowest concentrations, while no effects were observed at its medium concentration used in this study.

Agronomic characteristics and chemical composition of newly developed day-neutral strawberry lines by Agriculture and Agri-Food Canada.

The agronomic characteristics and chemical composition of seven advanced day-neutral strawberry lines and a commercial cultivar ‘Seascape’ were evaluated for their horticulture and quality attributes. The results showed that the advanced strawberry lines had the best horticultural characteristics, such as more resistance to diseases, less weight and juice losses and better fruit glossiness during storage, compared to ‘Seascape’. Among the advanced lines, FIN005–55 had the better fruit quality with higher soluble solids content (SSC)/titratable acidity (TA) ratio and highest SSC, FIN005–7 had the highest total phenolic content (TPC) and antioxidant capacity (AC), and both had potential for commercial trials.

Regulation of superoxide dismutase isoforms in resistant and susceptible strawberry cultivars subjected to leaf spot disease

Abstract Macroscopic symptoms were observed in two strawberry cultivars, with the degree of symptom intensity varying depending on the susceptibility of the cultivars, i.e. resistant or susceptible. The symptoms presented as red spots and were observed 30 d following leaf tissue inoculation with the Mycosphaerella fragariae pathogen. A comparison of the superoxide dismutase isoform profiles obtained by gel electrophoresis in all samples extracted from both resistant and susceptible cultivars indicated one constant sharp band, identified as Mn[sbnd]SOD with a molecular mass of 19 kDa. The intensity of this band was higher in all samples derived from the resistant cultivar than in those from the susceptible cultivar. Another superoxide dismutase (SOD) isoform, identified as CuZn[sbnd]SOD with a molecular mass of 16 kDa, was detected in all soluble proteins derived from the resistant cultivar. This isoform was not observed in the susceptible cultivar; however, following an incremental increase in the amount of loaded protein, it was illuminated as a faint band in a sample collected 3 d after inoculation, indicating insufficient production of the CuZn[sbnd]SOD isoform in the susceptible cultivar during an oxidative burst induced by the M. fragaria pathogen. Several bands were also characterized in both cultivars containing Fe and Mn as their co-factors (Fe, Mn[sbnd]SOD). Unlike in the resistant cultivar, where the activity of Fe, Mn[sbnd]SOD isoforms gradually and regularly increased and reached its highest level on the third day after inoculation, the activity of the isoforms changed irregularly over 20 days of study in the susceptible cultivar.

Potential link between fruit yield, quality parameters and phytohormonal changes in preharvest UV-C treated strawberry

Preharvest ultraviolet-C (UV-C) treatment of strawberry is a very new approach, and little information is available on the effect of this treatment on plant growth regulators. In this study, the effect of preharvest UV-C irradiations at three different doses on strawberry yield, fruit quality parameters and endogenous phytohormones was investigated simultaneously. The overall marketable yield of strawberry was not affected by the preharvest UV-C treatments, although more aborted and misshapen fruits were found in UV-C treated groups than in the untreated control. The fruits in the high dose group were firmer and had approximately 20% higher sucrose content and 15% higher ascorbic acid content than the control, while fruits from the middle and low dose groups showed no significant changes in these parameters. The lower abscisic acid (ABA) content found in the fruits in the high UV-C group may be associated with those quality changes. The citric acid content decreased only in the low dose group (reduction of 5.8%), with a concomitant 37% reduction in jasmonic acid (JA) content, compared to the control. The antioxidant status of fruits that received preharvest UV-C treatment was considered enhanced based on their oxygen radical absorbance capacity (ORAC) and malondialdehyde (MDA) content. In terms of aroma, three volatile alcohols differed significantly among the various treatments with obvious activation of alcohol acyltransferase (AAT) activity. The observed synchronous influence on physiological indexes and related phytohormones suggests that preharvest UV-C might affect fruit quality via the action of plant hormones.

Pre-harvest UV-C irradiation triggers VOCs accumulation with alteration of antioxidant enzymes and phytohormones in strawberry leaves

Recent studies have highlighted the biological and physiological effects of pre-harvest ultraviolet (UV)-C treatment on growing plants. However, little is known about the involvement of volatile organic compounds (VOCs) and their response to this treatment. In this study, strawberry plants were exposed to three different doses of UV-C radiation for seven weeks (a low dose: 9.6kJm-2; a medium dose: 15kJm-2; and a high-dose: 29.4kJm-2). Changes in VOC profiles were investigated and an attempt was made to identify factors that may be involved in the regulation of these alterations. Principle compounds analysis revealed that VOC profiles of UV-C treated samples were significantly altered with 26 VOCs being the major contributors to segregation. Among them, 18 fatty acid-derived VOCs accumulated in plants that received high and medium dose of UV-C treatments with higher lipoxygenase and alcohol dehydrogenase activities. In treated samples, the activity of the antioxidant enzymes catalase and peroxidase was inhibited, resulting in a reduced antioxidant capacity and higher lipid peroxidation. Simultaneously, jasmonic acid level was 74% higher in the high-dose group while abscisic acid content was more than 12% lower in both the medium and high-dose UV-C treated samples. These results indicated that pre-harvest UV-C treatment stimulated the biosynthesis of fatty acid-derived VOCs in strawberry leaf tissue by upregulating the activity of enzymes of the LOX biosynthetic pathway and downregulating antioxidant enzyme activities. It is further suggested that the mechanisms underlying fatty acid-derived VOCs biosynthesis in UV-C treated strawberry leaves are associated with UV-C-induced changes in phytohormone profiles.

Effect of Hyperbaric Treatment on Quality Attributes of Tomato Fruits

An experimental hyperbaric system was conceptualized, designed and built to explore the effect of hyperbaric treatment on the quality attributes of tomato.

Changes in ascorbate–glutathione pathway enzymes in response to Mycosphaerella fragariae infection in selected strawberry genotypes

Ten strawberry genotypes, resistant and moderately resistant (Joliette, Seascape, Aromas, FIN005-55 and FIN005-50) and susceptible ones (FIN00132-8, FIN00134-11, FIN00132-14, FIN005-7 and Kent) were used to assess the role of the antioxidative defence system against Mycosphaerella fragariae infection. The pathogen-induced changes of hydrogen peroxide (H2O2) and antioxidant enzymes ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) involved in the ascorbate–glutathione (ASC–GSH) cycle were examined in leaves of the selected genotypes. A significant different response was observed among the genotypes. A marked increase in H2O2 content, APX, MDHAR, DHAR and GR activities were observed in resistant and moderately resistant genotypes after inoculation by M. fragariae. In contrast, weak changes were observed in susceptible genotypes for the aforementioned enzymes and compounds. It seems that resistant genotypes capable of overproducing H2O2 have a higher capacity to scavenge and reduce the injury to strawberry leaves by regulating the ASC–GSH cycle. The results may be useful in future breeding programmes to select those individuals with high scavenging properties to breed new resistant lines.

EFFECT OF NON-UNIFORM HEAT TREATMENT ON TOMATO RIPENING AND CHILLING INJURY

Abstract An experimental setup consisting of a forced-air-twin-chambers insulated device was built to generate a non-uniform (heterogeneous) heat treatment. The heterogeneous treatment insured that half part of tomato in one chamber to be exposed to warm air at a controlled temperature of 39.5°C and uniformly circulating at a velocity of 0.24m s-1, while the other half in the other chamber was exposed under unheated, controlled and stable conditions (23°C, 0.24m s-1). Temperature control for both chambers along with the desired fixed air flow rate is achieved using suitable instrumentation. The tested tomatoes were randomly divided into five lots: one was used as control, two were uniformly treated, and the other two were heterogeneously treated. Immediately after treatment the fruit were transferred to regular storage at 14°C, to ripening at 20°C or to chilling injury (CI) at 4°C. Color, firmness, titratable acidity (TA), total soluble solid (TSS) and severity of CI were measured or evaluated subjectively at designed time. Results indicated there existence of statistically significant difference between heated and unheated part for tested tomatoes in terms of color, and CI. As result of relative consistently higher value of TA and TSS, no significant difference in the taste indictor, suger:acid (TSS:TA) ratio, was noticed. The result implied that ripening process of heated part was delayed in particular period, and this delay was similar to the contrast between uniformly heated tomato and its control. The observed difference might be explained by the fact that the effect of heat treatment on tomato is localized rather than systemic. These findings addressed that ensuring uniform heat condition is of paramount importance to attain the desired effect. It is suggested to develop systems with media such as RF or microwave, or to optimize the layout of material treated with conventional media.