西瓜叶片防御酶活性与枯萎病抗性的关系

Relationship between Leaf Defensive Enzyme Activities and Resistance to Fusarium Wilt in Watermelon

为了明确西瓜枯萎病抗性与抗氧化、次生代谢相关酶活性的关系,以西瓜枯萎病鉴别寄主(高抗品种PI296341-FR、轻抗品种Crimson Sweet和高感品种Sugar Baby)为材料,采用西瓜枯萎病菌孢子悬浮液进行人工接种,研究接种处理后西瓜叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)、多酚氧化酶(PPO)、苯丙氨酸解氨酶(PAL)、过氧化氢酶(CAT)活性的变化。结果显示,西瓜枯萎病菌接种处理后,3个西瓜品种叶片SOD、POD、PPO、PAL、CAT活性较未接种对照均有显著提高,抗病品种PI296341-FR和Crimson Sweet叶片的SOD、POD、PPO、PAL、CAT活性峰值出现时间早于感病品种Sugar Baby,酶活性增幅显著高于感病品种。抗病品种PI296341-FR和Crimson Sweet叶片的SOD、POD、PPO、CAT活性均在接种后2 d达到峰值,高抗品种PI296341-FR叶片的SOD、POD、PPO、CAT活性分别较未接种对照显著增加了58. 98%、26. 08%、69. 87%、78. 00%,较感病品种Sugar Baby显著增加了47. 62%、22. 75%、19. 91%、41. 79%;轻抗品种Crimson Sweet叶片的SOD、POD、PPO、CAT活性分别较未接种对照显著增加了73. 01%、22. 33%、62. 59%、63. 46%,较感病品种Sugar Baby显著增加了34. 56%、10. 10%、8. 14%、28. 40%。高抗品种和轻抗品种叶片的PAL活性分别于接种后2、1 d达峰值,分别较各自未接种对照显著增加了70. 70%、33. 34%,高抗品种叶片PAL活性较感病品种显著增加了20. 65%。而感病品种Sugar Baby叶片的5种酶活性均在接种后3 d才达到峰值。研究表明,SOD、POD、PPO、PAL、CAT 5种防御酶活性变化与西瓜抗病性密切相关,在西瓜枯萎病抗性生化机制中起重要作用,SOD、POD、PPO、PAL、CAT活性峰值大小及出现时间的早晚可作为西瓜枯萎病抗性筛选的重要生化指标。

To determine the relationships between activities of antioxidant,secondary metabolism related enzymes and resistance to Fusarium wilt in watermelon,three watermelon Fusarium wilt differential hosts(high resistant cultivar PI296341-FR,slight resistant cultivar Crimson Sweet,high susceptible cultivar Sugar Baby)were employed,and the dynamic changes of activities of superoxide dismutases(SOD),peroxydase(POD),polyphenol oxidase(PPO),phenylalanine ammonia lyase(PAL)and catalase(CAT)in different resistant watermelon cultivar leaves were analyzed after inoculation by the pathogen of Fusarium wilt.The results showed that activities of SOD,POD,PPO,PAL and CAT in watermelon leaves were significantly higher than the unioculated control.The increase rates of SOD,POD,PPO,PAL and CAT activities of resistant cultivar PI296341-FR and Crimson Sweet leaves were significantly higher than the susceptible ones and the activity peaks appeared earlier after inoculation by Fusarium oxysporum.The activities of SOD,POD,PPO and CAT of resistant cultivars PI296341-FR and Crimson Sweet reached the peak values on the second day after inoculation,which in high resistant cultivar PI296341-FR leaves were significantly increased by 58.98%,26.08%,69.87%and 78.00%compared with the uninoculated control,and by 47.62%,22.75%,19.91%and 41.79%compared with the susceptible cultivar Sugar Baby.The activities of SOD,POD,PPO and CAT in slight resistant cultivar Crimson Sweet leaves were significantly increased by 73.01%,22.33%,62.59%and 63.46%compared with the uninoculated control,and by 34.56%,10.10%,8.14%and 28.40%compared with the susceptible cultivar Sugar Baby.The PAL activities of high resistant cultivar PI296341-FR and slight resistant cultivar Crimson Sweet leaves reached the peak values separately on the second day and the first day,compared with the uninoculated control,which was significantly increased by 70.70%and 33.34%.Compared with the susceptible cultivar Sugar Baby,the activity of PAL in high resistant cultivar PI296341-FR leaves was significantly increased by 20.65%.However,the activity peaks of SOD,POD,PPO,PAL and CAT in high susceptible cultivar Sugar Baby appeared on the third day after inoculation.The results indicated that the change of SOD,POD,PPO,PAL and CAT activities in watermelon leaves was closely related to waterme-lon Fusarium wilt resistance,and the five defensive enzymes played an important role in resistant mechanism to watermelon Fusarium wilt.The activity peak value and emergence time of SOD,POD,PPO,PAL and CAT could be taken as important biochemical indexes for identification and screening of watermelon Fusarium wilt resistant cultivars.