Varying the time of red light exposure influences leaf resistance to different Botrytis cinerea isolates in strawberry

Light quality is an important determinant in the plant’s response to biotic stress. A low red: far-red ratio perception enhances plant susceptibility to pathogens. Increasing red wavelengths in the light spectrum may thus enhance the tolerance to pathogens. In this study, strawberry plants were exposed to increasing periods of red light replacing the full-spectrum white light in a 16 h photoperiod for, respectively, 5, 10 and 15 days. After the light pre-treatment, leaf resistance to three Botrytis isolates was evaluated. A diurnal rhythm of 6 h red light followed by 10 h white light during 15 days improved leaf resistance to all Botrytis isolates. Further finetuning of the light treatments showed that ten days of this light treatment followed by 5 days of 16 h white light could be the optimized light recipe to enhance leaf resistance to different Botrytis isolates in strawberry.