Blue lighting combined with cold storage temperature can suppress gray mold in strawberry fruit

Cold storage is an optimal way of preventing quality deterioration in fruit crops, and this is exemplified by strawberries. However, Botrytis cinerea, the causal agent of gray mold, is cold-adaptive and can cause losses to cold-stored fruit. This study evaluated the regulatory effects of the spectral quality of light on the fungal growth in vitro, and the development of gray mold on postharvest strawberries at both ambient (21 ℃) and cold (4 ℃) temperatures. None of the light qualities tested (white, blue, green, or red) significantly affected colony growth of B. cinerea compared with the dark conditions in which they were tested at 21 ℃. In fungal cultures kept at 4 ℃, blue light significantly retarded colony expansion compared to other light conditions and darkness. Moreover, blue light and cold conditions can synergistically result in an increased number of septa, hyphal abnormality and intracellular vacuoles. An enhanced accumulation of reactive oxygen species (ROS) was also observed in fungal hypha exposed to blue light under cold conditions. Infection assay on strawberries demonstrated that blue light caused insignificant and significant suppressive effects at 21 ℃ and 4 ℃, respectively. In addition, blue-light caused significant weight loss in strawberries compared with all other treatments. Consequently, blue-light illumination under cold conditions may result in oxidative stress to the B. cinerea cells, thus preventing this cold-adaptive pathogen from causing unexpected deterioration in the stored fruit.