Green LED irradiation promotes the quality of cabbage through delaying the senescence and regulating the glucosinolate metabolism

Abstract Light–emitting diode (LED) irradiation can affect postharvest vegetable and fruit shelf life and nutritional quality. In this study, 11 kinds of glucosinolates (GLS) and 6 types GLS breakdown products were identified in cabbage leaves. To investigate LED irradiation effects on quality and GLS metabolism, postharvest cabbage was irradiated with 25 μmol/(m2·s) green LED (GL) light under room temperature for 12 days. The dark condition and natural light were used as controls. GL irradiation inhibited the respiration rate and the accumulation of malondialdehyde, and maintained higher cabbage sensory score, chlorophyll content, and antioxidant enzyme activities, thus extending its postharvest shelf life. Additionally, GL irradiation promoted GLS profile accumulations, including glucoraphanin, glucoiberin, gluconapin, gluconasturtiin, glucobrassicin and sinigrin, which could have resulted from up-regulated expression of the transcription factors MYB28 and MYB51, and the key genes involved in GLS biosynthesis (CYP83A1, CYP83B1, ST5b and UGT74B1). Furthermore, GLS degradation was promoted by this treatment during the late stage of shelf-life, as higher myrosinase activity and relative MYR and ESM expression levels were found in treated cabbage leaves, resulting in higher isothiocyanate (ITC) and indole-3-carbinol contents after day 6. Therefore, GL irradiation was beneficial for cabbage preservation.