Comparison of nutritional values for dioscorea esculenta grown in a cultivated sub-tropical region and a plastic greenhouse in a cold region

Background The lesser yam (Dioscorea esculenta) is a phytochemical tuber that contains substantial amounts of diosgenin. Dioscorea esculenta is normally cultivated in tropical/sub-tropical regions such as African countries, and Okinawa in Japan. However, it remains unknown whether it can be successfully cultivated in cold regions within a plastic greenhouse. This study investigated the differences in nutritional values and diosgenin content between lesser yams cultivated in a sub-tropical climate (Okinawa) and those cultivated in a cold region (northern Kyoto) within a plastic greenhouse. Methods The tubers were planted in March 2021 and harvested in January 2022. The temperature of the plastic greenhouse was 25.6 °C throughout the cultivation period. Additionally, the soil properties were potting soil with 8 % nitrogen potassium phosphate. Samples of dioscorea esculenta from both regions were used to produce 1 kg of sliced tubers from six tubers, were dried with the peel, then pulverized. The diosgenin content was analyzed for each sample, and nutritional ingredients such as moisture, carbohydrates, protein, fat, ash, sodium, and energy were measured. Results Most of the analyzed nutritional ingredients demonstrated comparable values between plants cultivated in the sub-tropical region and within the plastic greenhouse in the cold region. The diosgenin content was 0.12 g/100 g for tubers cultivated in the sub-tropical region and 0.1 g/100 g for those cultivated in the cold region within a plastic greenhouse. Conclusion Nutritional ingredients and diosgenin contents were comparable between the two growing conditions. Dioscorea esculenta can be cultivated in sub-tropical regions and in cold regions within plastic greenhouses.