关键词: 萝卜, 高温干旱复合胁迫, 生理生化指标, 综合评价, 耐旱品种

Abstract: During the radish sowing season in Chongqing and its surrounding areas，radishes often face the combined stress of high temperature and drought.To establish a multi‐index comprehensive evaluation system for radish drought tolerance under combined high temperature and drought stress and screen drought‐resistant radish genetic resources，11 radish varieties（lines）were used as materials.After 40 ℃ high temperature and water cessation treatment for 0，2，6，12，24，and 48 h in 5—6 leaf radish seedlings，the plant height，aboveground fresh weight，underground fresh weight，superoxide dismutase（SOD），ascorbate peroxidase（APX），catalase（CAT），peroxidase（POD）activities，malondialdehyde（MDA）content，and chlorophyll fluorescence parameters（F₀，F_m，F_v/F_m）were measured.The drought tolerance of radishes under combined high temperature and drought stress was comprehensively evaluated by using the membership function analysis and principal component analysis.The results showed that all radish varieties（lines）died after 48 h of stress. With the intensification of high‐temperature and drought stress，the relative plant height，aboveground fresh weight and underground fresh weight of different radish varieties（lines）showed a downward trend.The relative activities of APX，POD and SOD first increased，then decreased and then increased again，while the relative CAT activity first increased and then decreased.The relative MDA content first increased，then decreased and then increased again.The 6—12 h of stress was the key response period.The relative APX and CAT activities were the highest at 6 h of stress，the relative SOD and POD activities significantly decreased after 2 h of stress and then increased after 12 h of stress，and the relative MDA content decreased to the lowest at 6 h.The relative F_v/F_m and Fm decreased to the lowest after 24 h of drought.According to the comprehensive evaluation results of all indicators，the drought tolerance of the 11 radish varieties（lines）from strong to weak was Fuling wild radish，Changshou wild radish，BZ2，Lanhuazi，Hongxing cherry radish，ZY228，Baidingshui radish，Changhong No.1，Xichang white，ZY147，and ZY4.The constructed multi‐index evaluation system can effectively identify the drought tolerance of radishes under combined high temperature and drought stress and screen drought‐resistant varieties. Chlorophyll fluorescence parameters（F₀，F_m），SOD，CAT activities can be used as important traits for rapid identification of radish drought tolerance in areas with frequent high temperature and drought.

Key words: Radish, High‐temperature and drought stress, Physiological and biochemical indicators, Comprehensive evaluation, Drought‐tolerant variety