Resistance Identification Of Hamimelon Varieties To Acidovorax Avenae Subsp. Citrulli And Studies On Mechanism Of Disease Resistance

Thirteen varieties of Hamimelon were identified by the methods of natural infection in open field and artificial inoculation .It was found that the difference was obvious among varieties. The immune varieties were not found ,the high resistance varieties accounted for 7.69%,the middle resistance was 46.15%,the middle sense was 23.78%,the sense was 23.08 %. The study on mechanism of disease resistance though observing surface structure of leaves and determining physiological and biochemical indexes. Leaves of Hamimelon were observed by scan electron microscope. The results indicated : The stomata shape and size between the resisting disease type ( Kangbinghongcuibao) and the infecting disease type (Xinmiza No.7 8601) were insignificant,but the stomata density of Kangbinghongcuibao is higher than very much. Besides,the leaf pile shape of Kangbinghongcuibao and Xinmizai No.7 8601 was similar,but the leaf piles of Kangbinghongcuibao were longer than Xinmizai No.7 8601, and the quantity of pile was more than Xinmizai No.7 8601 obviously. These phenomenon provided important morphology foundation for the superiorities of the resisting disease types. Hamimelon varieties with different disease resistance were inoculated by Acidovorax avenae subsp. citrulli. The activity of peroxidase(POD), polyphenol oxidase(PPO),phenylalanine ammonialyase(PAL) and superoxide dismutase(SOD), content of lignin,content of soluble protein and content of total sugar were investigated before and after inoculation . The results indicated: no relationships were found between disease resistance and the activity of POD, PAL, and SOD, lignin content before inoculation. the activity of PPO,soluble protein content and total sugar content were related to disease resistant of Hamimelon before inoculation. After inoculation, positive relationship was found between changes of POD, PPO and PAL, lignin content and total sugar content. Changes of SOD activity was negative relationship, but changes of soluble protein content with disease resistance were not correlativity obviously.