Red, blue and far-red light affect strawberry plant development and fruit quality without changing the susceptibility to Botrytis cinerea infection

Light regulates plant development, fruit quality characteristics and pathogen defense through primary and secondary metabolism. We investigated the effects of light spectrum on plant development, the levels of primary and secondary metabolites and fungal susceptibility in strawberry fruit harvested in turning and red ripe stages. Strawberry plants were grown in a climate chamber under different red (R) to blue (B) light ratios with and without ∼50 μmol m^–2 s^–1 additional far-red (FR) light. A total photosynthetic photon flux density (PPFD) of ∼180 μmol m^–2 s^–1 was applied with a 16 h day length. Low R to B light ratios resulted in lower levels of sucrose but higher levels of ascorbic acid, proanthocyanidin, (E)-2-hexenal and (Z)-3-hexenol in fruit. No effects of R to B ratios on plant morphology, flowering time and fruit set were observed. Additional FR light increased plant height, accelerated flower and fruit formation; decreased levels of ascorbic acid and anthocyanins but increased levels of soluble sugar and strawberry flavor-related volatiles. Fruit susceptibility to B. cinerea was not affected by the light treatments.