关键词: 西瓜, 种质, 生理指标, 低温胁迫

Abstract: 【Objective】To screen watermelon germplasm materials with low temperature tolerance,explore breeding physiological indexes,and provide materials and theoretical reference for breeding of low temperature tolerant watermelon varieties.【Methods】Using 30 watermelon varieties（lines） as experimental materials,the effects of low temperature stress on the chilling injury index and recovery index of watermelon seedlings were analyzed by simulating low temperature stress（7.5 ℃） in an incubator. Furthermore,Zaojia 8424 and Qianli No.4 were selected as the test materials to analyze the effects of long-term low temperature stress （8 ℃ for 15 days）,short-term low temperature stress （4 ℃ for 2 days） and normal temperature recovery growth（28/22 ℃ for 5 days） on antioxidant enzyme activity,malondialdehyde content,reactive oxygen species content and osmotic adjustment substance content of watermelon seedlings.【Results】There were significant differences（P<0.05） in chilling injury index and no significant difference（P>0.05） in recovery index among different watermelon materials under low temperature stress of 7.5 ℃. Five materials （Qianli No.2,Qianli No.3,Qianli No.4,18S-135-2 and 18S-145-1） selected from middle fruit type had significantly （P<0.05） stronger tolerance to low temperature than Zaojia 8424（CK1）. The ability of low temperature tolerance of 2 materials（17A-79×17A-82 and 17A-82×17A-79） selected from small fruit type was stronger than that of Xiaolan（CK2）. The changes of antioxidant enzyme activities,osmotic adjustment substance content and reactive oxygen species content of Zaojia 8424 and Qianli No.4 seedlings were different under different low temperature treatment（short-term low temperature stress and long-term low temperature stress）. Qianli No.4 had higher antioxidant enzyme activity,soluble protein content and soluble sugar content,and lower content of malondialdehyde,superoxide anion（O₂^-） and hydrogen peroxide（H₂O₂）,the content of proline of Zaojia 8424 and Qianli No.4 varies with different low temperature treatments.【Conclusion】Thirty watermelon varieties （lines） had different tolerance and physiological response to low temperature stress. Low temperature tolerant germplasm materials were Qianli No.2,Qianli No.3,Qianli No.4,18S-135-2,18S-145-1,17A-79×17A-82 and 17A-82×17A-79.

Key words: Watermelon, Germplasm, Physiological index, Low temperature stress