Plant morphological characteristics for year-round production and its fruit quality in response to different light wavelengths in blueberry

Abstract

In Japan, regular blueberry harvest season is very limited, from June to September. Due to the increased demand of Japanese customers, year-round production of blueberry fruit has become important to compensate the amount of import of fresh and frozen blueberry. Therefore, in Tokyo University of Agriculture and Technology (TUAT), we established a plant factory controlled environment with four seasons to develop new cultivation methods for year-round production by accelerating plant's life cycle. In this study, we investigated morphological characters of blueberry plants for year-round production and its fruit quality in response to different light wavelengths using light-emitting diodes (LEDs) in the plant factory. Three-year-old 'Sharpblue' plants were irradiated with 100% blue (B) (459 nm), 100% red (R) (631 nm), 1:1 = red:blue (R and B), respectively. Fluorescent light (F) was used as control. Other environmental factors were set the same for all treatments and control. At 165 days after treatment, (R and B) treated plants and control ones showed satisfying vegetative growth with flowers and high potential for continuous flowering, while plants under (B) were retarded in growth with cessation of shoot elongation, showing low potential for continuous flowering although many flowers were observed during the study. However, the strongest plant vigor with bigger leaves but few flowers were found in plants treated with (R). In terms of fruit quality, higher Brix% and less acidity were found in fruits under (R and B) and (B) than in those of the other plants applied with (R) and (F). Bigger fruit size and heavier fruit weights were found in plants under (R and B). Thus, these results suggest that light quality has a strong influence on continuous flowering for year-round and high-quality fruit production in blueberry.