Seasonal Variation in Nutritional Substances in Varieties of Leafy Chinese Kale (Brassica oleracea var. alboglabra): A Pilot Trial

Chinese kale (Brassica oleracea var. alboglabra), a native Chinese vegetable, is usually grown for its bolting stems as the common edible part. However, the tender leaves of the vegetable have higher nutritional value. To investigate the effects of cultivation seasons on the nutritional substances in leafy Chinese kale, we conducted a pilot trial to analyze the differences in the content of nutritional substances, including glucosinolates, in five varieties of leafy Chinese kale (JLYC-01, JLYC-02, JLYC-03, JLYC-04, JLYC-05) cultured in fall, winter, and spring. The plant weight was 27.2 g–40.4 g in spring, 20.0 g–38.6 g in winter, and 20.3 g–34.0 g in fall, and the JLYC-05 variety showed superiority among the varieties, with weights of 34.0 g in fall, 38.6 g in winter, and 39.7 g in winter. Overall, the nutritional substance content in leafy Chinese kale cultivated in spring and fall was better than that of those cultivated in winter, providing a key reference for leafy Chinese kale planting. Among the five varieties, JLYC-04 and JLYC-05 are excellent candidates for future breeding programs, since JLYC-04 has a higher content of total phenols (10.1 mg GAE g−1 DW–10.7 mg GAE g−1 DW) and glucosinolates (5.8 μmol g−1 DW–7.1 μmol g−1 DW), exhibiting strong antioxidant capacity, while JLYC-05 contains more chlorophyll (157 mg 100 g−1 FW–214 mg 100 g−1 FW) and carotenoids (31.8 mg 100 g−1 FW–39.1 mg 100 g−1 FW).