Variation among Strawberry Cultivars in Bruising Susceptibility Related to Wound Ethylene Production and Sensitivity

Bruising of strawberry (Fragaria ×ananassa Duch.) fruit is a common mechanical injury that reduces product value. Wound-induced ethylene may accelerate deterioration or decay, affecting strawberry quality and shelf life. However, bruising susceptibility varies among strawberry cultivars. In this study, cultivars Monterey, Sweet Sensation, Radiance, and two proprietary cultivars (Cultivar A and Cultivar B) from a private breeding program were investigated to evaluate their bruising susceptibility and wound response. Bruising consisted of dropping a 28-g steel ball from 27 cm onto individual fruit; unbruised fruit were the primary control, while fruit exposed to 1 μL·L−1 ethylene were used as a check for ethylene response. All fruit were stored at 20 °C, 90% relative humidity (RH), with respiration and ethylene production measured at 2-hour intervals for 24 hours. Appearance observations were recorded daily until decay onset. Peak respiration rates of 30–40 mL CO2·kg−1·h−1 mostly occurred within 4 hours (‘Cultivar B’) to 6 hours (‘Cultivar A’ and ‘Sweet Sensation’) after bruising, except ‘Monterey’, which peaked at 60 mL CO2·kg−1·h−1 in 2 hours, and ‘Radiance’, which reached 70 mL CO2·kg−1·h−1 in 6 hours. Maximum ethylene production rates after bruising were 0.05 to 0.06 μL·kg−1·h−1 for ‘Monterey’, ‘Cultivar A’, and ‘Cultivar B’, 0.10 μL·kg−1·h−1 for ‘Sweet Sensation’, and 0.20 to 0.37 μL·kg−1·h−1 for ‘Radiance’. ‘Cultivar B’, with the lowest ethylene production, exhibited the lowest overall bruising severity, whereas ‘Radiance’, with the highest ethylene production, exhibited the most severe bruising-induced water soaking, and the other cultivars were intermediate, although ‘Monterey’ bruises were more discolored than those of the other cultivars. ‘Monterey’, ‘Radiance’, and ‘Sweet Sensation’ showed more yellowing and browning of the calyx in response to both bruising and ethylene exposure than ‘Cultivar A’ and ‘Cultivar B’. Except for ‘Cultivar B’, bruising and ethylene exposure increased decay severity.