Physiological Response and Resistance Analysis of Different Flue-cured Tobacco Varieties to Bacterial Wilt

In order to clarify the response mechanism of flue-cured tobacco varieties (lines) with different resistance to Ralstonia Solanacearum infection, resistant varieties (lines)Yanyan 97, G80, 633K and susceptible varieties Cuibi No.1, Honghuadajinyuan were used as materials, and disease incidence, dry weight, hormones, Malondialdehyde content and antioxidant enzyme activities of different varieties (lines) were studied under Ralstonia Solanacearum infection. The results showed that incidence rate and disease index of the susceptible varieties were higher than those of the resistant varieties. The incidence rate and disease index of Honghuadajinyuan and Cuibi No.1 reached 80%, 68.89 and 70%, 41.11, respectively; Compared with no Ralstonia Solanacearum infection(CK), the dry weight and malondialdehyde (MDA) content of all varieties (lines) decreased significantly after Ralstonia Solanacearum infection. The decrease of dry weight in the resistant varieties (lines) was significantly less than that of the susceptible varieties. The decrease in dry weight of 633K was the smallest, 37.47%, and the decrease of the dry weight of Honghuadajinyuan was the largest, 84.01%. The decrease of MDA content in the resistant varieties (lines) was significantly greater than that in the susceptible varieties. 633K had the largest decrease of 45.67%, and Honghuadajinyuan had the smallest decrease of 13.02%; After Ralstonia Solanacearum infection, the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) of all varieties were significantly increased, and the increase of the resistant varieties (lines) was greater than that of the susceptible varieties; Jasmonic acid (JA) and salicylic acid (SA) contents of the resistant varieties (lines) were significantly up-regulated. For the susceptible varieties SA contents were significantly up-regulated but JA contents were significantly down-regulated. Under the Ralstonia Solanacearum infection, the disease resistant varieties can respond more effectively to bacterial wilt infection, so as to resist the infection of pathogenic bacteria.