Evaluation of Cold Tolerance of Five Sweet Potato Varieties by Membership Function Method

Key words: 
• Membership function method /
• vegetable sweet potato /
• low temperature stress /
• physiological and biochemical parameters /
• cold tolerance evaluation

Abstract: Low temperature is a major factor restricting cultivation of vegetable sweet potato in winter and spring,in Hainan,China. In order to explore the mechanism of cold injury and evaluate the cold tolerance of vegetable sweet potato varieties,five vegetable sweet potato varieties were chosen as material to determine their physiological and biochemical parameters under the temperatures of 25,15,5 ℃ in the artificial climate chamber,and the resultant data were analyzed by using the membership function method to evaluate the cold tolerance of the varieties. The result showed that five vegetable sweet potato leaves treated at a lower temperature increased their relative electrical conductivity,malondialdehyde（ MDA） cell damage index,and that catalase（ CAT）,peroxidase（ POD） activity,and the contents of proline（ Pro）,soluble sugar and protein increased as the treatment temperature decreased. The parameters and their changes of the varieties were different. The membership function based comprehensive evaluation showed that the five vegetable sweet potato varieties had a cold tolerance in the order of Pushu53 ＞ Hainan local varieties ＞ Xucaishu 1 ＞ Xuzi caishu 8 ＞ Guangshucai 2 at the temperature of 15 ℃;Pushu53 ＞ Hainan local varieties ＞ Xuzicai 8 ＞ Xucaishu 1 ＞ Guangshucai 2 at the temperature of 5 ℃.