Blue LED Irradiation Induces Scoparone Production in Wounded Satsuma Mandarin ‘Aoshima Unshu’ and Reduces Fruit Decay during Long-term Storage

Abstract

In the present study, we examined the effect of blue LED irradiation on production of phytoalexin scoparone in wounded satsuma mandarin fruit as a result of fungal infections, as well as the effect of tape-type blue LED on fruit decay during long-term storage (from December to April) in an actual storage room. The blue LED treatment reduced the rate of fruit decay compared to that of dark treatment in wounded fruits. The decay rate of LED irradiated fruit was 13.3%, while that of non-irradiated fruit was 51.1%. In wounded fruits, blue LED treatment resulted in significantly higher scoparone contents than dark treatment. Intact (non-wounded) fruits had low scoparone contents, irrespective of blue LED irradiation. In an examination of changes in total fruit decay rate during storage using tape type-blue LED, the total decay rate was not significantly different between the LED-treated and untreated fruits until 64 days after storage (36 days after starting LED irradiation). On the other hand, at 92 and 120 days after the start of storage, total fruit decay under blue LED treatment was significantly lower compared to the untreated control. The tape-type blue LED (10 μmol·m −2 ·s −1 ) did not affect either the fruit quality analyzed (soluble solid content, titratable acidity, specific gravity, percentage of flesh) or the rind color. These results indicate that blue light induces scoparone production in wounded satsuma mandarin, and because of this, along with other putative factors, tape-type blue LED irradiation reduces mandarin fruit decay during long-term storage.

Blue Light Does Not Affect Fruit Quality or Disease Development on Ripe Blueberry Fruit During Postharvest Cold Storage

“…In lettuce, blue light increased vitamin C and polyphenolic content during storage without affecting pH and moisture content [42]. Additionally, blue light promoted anthocyanin accumulation, delayed pathogen growth and prolonged shelf-life in certain fruits [20,28,29,32,35,[43][44][45]. In our study, blue light did not consistently affect postharvest fruit storage attributes, which included visual quality, fruit softening, skin toughness, TSS content, TA and weight, compared with dark and white light treatments.…”

Coordinated activation of the metabolic pathways induced by LED blue light in citrus fruit

“…So it is worth pointing out that plant OMTs constitute a large family of enzymes that methylate the oxygen atom of a variety of secondary metabolites, which leads to the synthesis of lignin, and also of different classes of alkaloids and phenylpropanoids (Buchanan, Gruissem, & Jones, 2000;Dixon, Hawkins, Hussey, & Edwards, 2009), including isoflavonoids, flavonols, flavones and anthocyanins, and coumarins like scoparone, which is induced by LBL in citrus fruit peel (Ballester & Lafuente, 2017;Yamaga & Nakamura, 2018). In fact the results indicated the over-representation of the 'biosynthesis of coumarins, flavonols and stilbene' (Table 1).…”

Light: An Alternative Method for Physical Control of Postharvest Rotting Caused by Fungi of Citrus Fruit

“…After the inoculation of the blue mold fungal pathogen, blue light reduces the sporulation and mycelium of P. italicum, while the 6-day irradiation period before the inoculation with pathogen showed less symptom development [81]. Another study claims that when blue light was exposed on the wounded satsuma mandarin fruits under storage conditions, it enhanced the production of phytoalexin scoparone and the blue light treated fruits had only 13.3% decayed fruits, where the nontreated fruits had 51.1% fruit decay caused by P. digitatum and P. italicum [77]. Direct exposure of blue light in in vitro conditions reduces the citrus decay rates caused by the P. italicum and P. citri.…”

“…ese studies further highlighted that blue light treatment has no effects on the rind color nor affects fruit quality parameters (soluble solid content, titratable acidity, specific gravity, and percentage of flesh) [77]. e citrus peels are rich in oils which contain lipid-derived constituents having antifungal activity [83].…”