The roles of methyl jasmonate (MJ) in lum fruit ripening, ethylene biosynthesis, and fruit quality were investigated using exogenous applications of MJ. Mature fruit of the early-, mid-, and late-maturing Japanese plum (Primus salicina Lindl.) cultivars 'Black Amber', 'Amber Jewel', and 'Angelino', respectively, were harvested at commercial maturity and exposed to 0,10 -5, or 10-3 M MJ vapour treatments at 20° ± 1°C for 12 h. Post-harvest MJ treatments accelerated fruit ripening processes in 'Black Amber', 'Amber Jewel' and 'Angelino' plum. Respiration rates, ethylene production, the activities of the ethylene biosynthetic enzymes 1-aminocyclopropane-1-carboxylic acid synthase (ACS) and 1- aminocyclopropane-1- carboxylic acid oxidase (ACO), and the content of 1-aminocyclopropane-1- carboxylic acid (ACC) increased in MJ-treated fruit. Treatment with 10 3 M MJ advanced the ethylene climacteric in 'Black Amber' and 'Angelino' fruit by 2 d, compared to untreated fruit. Fruit exposed to MJ exhibited typical climacteric patterns of ACS and ACO activities, while control fruit did not show climacteric peaks in the activities of these enzymes. Application of MJ advanced the respiratory climacteric peak by 1 d in 'Amber Jewel' and 'Angelino' fruit, compared to control fruit. During fruit ripening, soluble solids contents (SSC) increased while titratable acidity (TA) decreased in MJ-treated fruit of all three cultivars. MJ application to 'Amber Jewel' and 'Angelino' fruit improved their colour in terms of L*, a*, b*, chroma and hue angle, while 'Black Amber' fruit did not exhibit any changes in colour parameters. MJ treatment also increased the synthesis of ascorbic acid, total carotenoids, and total anti-oxidants during fruit ripening in all cultivars.
"Skin was removed on two opposite sides of each fruit along the equatorial axes and then the chroma (c*), lightness (L) and a* and b* values were measured using a colorimeter (Konica Minolta CR400 Chroma Meter, Konica Minolta Sensing, Inc., Osaka, Japan). The hue angle (H • ) that represented changes in primary colors was calculated . Flesh firmness was measured using a Güss FTA Penetrometer with an 8 mm tip (Güss, Strand, Western Cape, South Africa). "
[Show abstract][Hide abstract] ABSTRACT: a b s t r a c t During ripening fruits undergo several physiological and biochemical modifications that influence quality-related properties, such as texture, color, aroma and taste. We studied the differences in eth-ylene and sugar metabolism between two genetically related Japanese plum cultivars with contrasting ripening behaviors. 'Santa Rosa' (SR) behaved as a typical climacteric fruit, while the bud sport mutant 'Sweet Miriam' (SM) displayed a non-climacteric ripening pattern. SM fruit displayed a delayed ripening that lasted 120 days longer than that of the climacteric fruit. At the full-ripe stage, both cultivars reached similar final size and weight but the non-climacteric fruits were firmer than the climacteric fruits. Fully ripe non-climacteric plum fruits, showed an accumulation of sorbitol that was 2.5 times higher than that of climacteric fruits, and the increase in sorbitol were also par-alleled to an increase in sucrose catabolism. These changes were highly correlated with decreased activity and expression of NAD + -dependent sorbitol dehydrogenase and sorbitol oxidase and increased sorbitol-6-phosphate dehydrogenase activity, suggesting an enhanced sorbitol synthesis in non-climacteric fruits.
"Contrarily, enhanced expression of ethylene biosynthetic genes has been found in pear by MeJA treatment (Kondo et al., 2007). On the other hand, postharvest 1 mM MeJA treatment increased and advanced ethylene production in 3 plum cultivars, by increasing ACS and ACO activities (Khan and Singh, 2007). "
[Show abstract][Hide abstract] ABSTRACT: ‘Black Splendor’ (BS) and ‘Royal Rosa’ (RR) plums were treated preharvest with methyl jasmonate (MeJA) at three concentrations (0.5, 1.0 and 2.0 mM) along the on-tree fruit development: 63, 77 and 98 days after full blossom (DAFB). Both control and treated fruit were harvested at the commercial ripening stage and stored in two temperature conditions: 9 days at 20 °C or at 2 °C + 1 day at 20 °C for 50 days. Preharvest MeJA at 2.0 mM significantly accelerated whereas 0.5 mM delayed the postharvest ripening process for both cultivars, since ethylene production, respiration rate and softening were reduced significantly at the two storage conditions for 0.5 mM. In these fruit, total phenolics, total antioxidant activity (hydrophilic fraction, HTAA) and the antioxidant enzymes peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) were found at higher levels in treated than control plums during postharvest storage, which could account for the delay of the postharvest ripening process and the extension of shelf-life.
"The application of MeJA inhibited Colletotrichum acutatum in loquat (Cao et al., 2008) and induced disease resistance to Botrytis cinerea in tomato (Yu et al., 2009), probably due to the systemic acquired resistance (SAR) as a signal molecule (Beckers and Spoel, 2005). As a postharvest treatment, MeJA accelerates also the rate of fruit ripening in climacteric fruit, such as mango, peach, tomato and apple through promotion of ethylene biosynthesis (Peña -Cortés et al., 2005), as well as in plum (Khan and Singh, 2007). Additionally, MeJA induced increases in flavonoid and anthocyanin compounds during cold storage of bayberry and blackberry (Wang et al., 2008, 2009). "
[Show abstract][Hide abstract] ABSTRACT: Two plum (Prunus salicina Lindl.) cultivars ‘Black Splendor’ (BS) and ‘Royal Rosa’ (RR) were treated with methyl jasmonate (MeJA) at 3 concentrations (0.5, 1.0 and 2.0 mM) along the on-tree fruit development: 63, 77 and 98 days after full blossom (DAFB). On a weekly basis, fruit samples were taken for measuring fruit size and weight and parameters related to quality. Results revealed that MeJA was effective in increasing fruit size and weight, the 0.5 mM being the most effective for BS cultivar and 2.0 mM for RR. At harvest, those fruit treated with 0.5 mM MeJA had the highest firmness and colour Hue values. Total acidity was also generally higher in MeJA-treated fruit than in controls, while the content of total soluble solids remained unaffected. In addition, total phenolics and total antioxidant activity were found at higher concentrations in 0.5 and 2.0 mM MeJA-treated than in control fruit over at last 3 weeks of fruit development for BS and RR cultivars, respectively. Overall results suggest that MeJA could be a promising preharvest tool to increase plum size and quality with enhanced bioactive compounds and antioxidant activity, although the optimum concentration is cultivar dependent.
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