2018 ASHS Annual Conference

Light-emitting diodes (LEDs) becomes popular supplemental lighting (SL) in greenhouse because of high illuminating efficiency without compensating crop productivity. Accumulation of phytochemicals can be also induced by LEDs with specific spectrum in many crop species. Besides phytochemicals, mineral nutrients are essential for human nutrition and contribute to the quality and flavor of tomatoes. Ion uptake, partitioning, and assimilation are mediated by phytochrome, whose actions highly depend on red (600-700 nm) and far-red (700-750 nm) light. The objectives of this study were to determine how red and far-red light affects fruit mineral composition and taste of greenhouse tomato. ‘Merlice’ scions grafted onto ‘Maxifort’ rootstocks were supplemented with (FR, 29% far-red ∶71% red) or without (R, 100% red) far-red LEDs lighting, compared with the most common SL, high-pressure sodium (HPS) lamps. Tomatoes at the stage 6 were selected for mineral and sensory evaluation. The concentration of nitrate, nitrite, sulfate, phosphate, chloride, sodium, potassium, magnesium, and calcium in fruit were determined by ion chromatography. The ends of the tomatoes were cut off and then the tomatoes were cut into fourths. Panelists were given one piece of each sample, sequentially with sample order being randomized, and were asked to rate the degree of liking (DOL) regarding aroma, sweetness, saltiness, acidity, and texture on a 9-pt scale as well as aroma, sweetness, saltiness, acidity, and texture on a 5-pt just about right (JAR) scale. The panelist was given water and a cracker to cleanse their palate between samples. When complete, the panelist was given a $5 gift card as reward. The concentration of sodium and dry matter ratio were increased significantly by FR, compared to R and HPS. Interestingly, there was a significant difference between the samples for DOL on aroma (FR was rated higher than R), sweetness (FR was rated higher than HPS and R), saltiness (FR was rated higher than HPS), acidity (FR was rated higher than HPS and R), and texture (FR was rated higher than R). Like DOL, there was a significant difference between the samples for JAR on sweetness (FR was rated higher than HPS and R), and texture (FR was rated higher than R). Our results suggest that supplemental lighting with far-red LEDs induces the accumulation of sodium and dry matter in fruit, and that customers can tell the chemical differences from aroma, sweetness, saltiness, acidity, and texture.