Strawberry Ripening Research Articles

Effect of exogenous application of gibberellic acid on color change and phenylalanine ammonia-lyase, chlorophyllase, and peroxidase activities during ripening of strawberry fruit (Fragaria x ananassa Duch.)

The effect of exogenously applied gibberellic acid (GA3) on the postharvest color change of strawberry fruit was evaluated through their external color and surface color parameters. A significant delay on color evolution was observed in fruits treated with GA3. The evolution of activities of phenylalanine ammonia-lyase (PAL), chlorophyllase, and peroxidase was also analyzed. PAL activity increased during strawberry ripening, but in fruits treated with GA3 the increase in such activity was slower, and, probably as consequence, the development of red color was delayed. Moreover, the activity of chlorophyllase and peroxidase, enzymes possibly involved in chlorophyll metabolism, decreased during strawberry ripening. However, a delay was observed in the decrease of such activities in GA3-treated fruits.

Foliar Application of Calcium Chloride Delays Postharvest Ripening of Strawberry

Effects of CaCl2 preharvest treatment on postharvest strawberry (Fragaria × ananassa) ripening and gray mold development were assessed. Two experiments were carried out in 1987 on two sites. In the first experiment, the effects of rate of application of CaCl2 and degree of fruit maturity at treatment were studied with the conventional cultivar Kent. In the second experiment, the influence of concentration and frequency of application of CaCl2 was investigated with day-neutral `Tribute'. Calcium treatment caused a significant increase in fruit and leaf Ca contents, which were closely correlated. The degree of fruit maturity at application and the frequency of treatment did not affect Ca concentration in the tissues. Several maturity criteria were measured during fruit storage in air at 4C. Anthocyanin and free-sugar contents and tissue electrical conductivity increased, while titratable acidity and firmness decreased. In both experiments, Ca treatment delayed ripening and gray mold development. The delay increased with increasing Ca concentration.

Cellulase activity and ethylene in ripening strawberry and apple fruits

A six-fold increase in cellulase activity, measured as the reduction in viscosity of carboxymethyl cellulose, was associated with maturation and softening in strawberry fruit. Applied ethylene did not increase cellulase levels in harvested strawberry fruit. This agrees with earlier findings that ethylene does not appear to regulate strawberry ripening. In apple, an ethylene-sensitive fruit, a decrease in cellulase activity was observed in fruit allowed to ripen on the tree.

Rowcover Material and Time of Application and Removal Affect Ripening and Yield of Strawberries

Abstract Effects of time of application and removal of straw, clear polyethylene, black polyethylene, polypropylene, and polypropylene–polyamid rowcovers were measured for ‘Earliglow’ and ‘Allstar’ strawberries (Fragaria × ananassa Duch.). There was no consistent effect of date of autumn application on yield or fruit size for the polypropylene cover. All winter-applied rowcovers resulted in improved yields relative to uncovered plots, although this difference was not always significant. When applied during early spring, opaque materials reduced yields up to 46% and delayed fruiting as much as 3 days, while some translucent materials enhanced yields as much as 94% and accelerated harvest by 8 days compared to uncovered strawberries. Covering with translucent materials during both winter and spring had even stronger positive effects, with ‘Earliglow’ being more responsive. With translucent rowcovers, the time of removal had a greater effect on production and fruit size than rowcover type. Optimal removal dates differed for rowcover type and cultivar. For a short period of time in early spring, rowcovers apparently provide an environment favorable for flower development.