Water Soaking Disorder in Strawberries: Triggers, Factors, and Mechanisms

Abstract

Water soaking is an important surface disorder of strawberries that limits unprotected field production. The objective was to identify the mechanism(s) of water soaking. Symptomatic fruit show pale, deliquescent patches of skin. This damage extends into the flesh. Numerous cuticular microcracks occurred in water-soaked areas. Water soaking occurred only if the skin was exposed to liquid water. Water soaking was more rapid when the cuticle had been abraded. Water soaking, anthocyanin leakage, and water uptake all increased with incubation time. There was a lag phase for water soaking and anthocyanin leakage, but not for water uptake. Susceptibility to water soaking increased with fruit ripening and mass. Incubation in isotonic PEG 6000 increased cuticular microcracking but decreased water soaking and water uptake. Incubation in hypotonic fruit juice (natural and artificial) increased water soaking incidence and severity but reduced water uptake. Incubation in dilute citric and malic acids increased plasma membrane permeability as indexed by anthocyanin leakage and increased water soaking. Thus, water soaking involves cuticular microcracking, localized water uptake, bursting of cells, and the release of organic acids into the apoplast. The damage propagates from cell to cell.

Azacytidine arrests ripening in cultivated strawberry (Fragaria × ananassa) by repressing key genes and altering hormone contents

“…Injection reaches all tissues and is thus a more direct application method than surface spraying is. Indeed, the latter may lead to water soaking fruit damage and not penetrating the fruit due to wax layer [ 45 ]. Many other aspects should be considered when attempting to explain these differences, including the use of a different cultivar, the in vivo vs in vitro treatment, greenhouse vs growth chamber, constant or variable temperature.…”

Calcium ions decrease water-soaking in strawberries

“…It develops when fruit is exposed to rain during ripening. Protected cultivation in greenhouses or tunnels covered with plastic film generally avoids water soaking [ 2 ] but it markedly increases the cost of production. Other countermeasures for water soaking are not known.…”

“…Recently, the physiological background of water soaking has been identified [ 2 ]. In many ways the process of water soaking in strawberry resembles the process of rain cracking in sweet cherry.…”

“…Both, water soaking and rain cracking are multistep processes that can be described using the analogy of a ‘zipper’, that unzips the fruit skin [ 3 ]. Based on the ‘Zipper’ model [ 3 ], water soaking is initiated by the formation of microscopic cracks (‘microcracks’) in the cuticle [ 2 ]. Microcracking impairs the barrier function of the cuticle thereby permitting localized water uptake.…”

“…Exposure to these acids increases the permeability of the membranes of adjacent cells. This causes water soaking to spread tangentially over the skin and also radially down into the flesh [ 2 ].…”