Disease Resistance Screens On Different Cultivars And BTH Or Harpin Treatment Induces Resistance In Muskmelons (Cucumis Melon L.)

Five major cultivars in Gansu were sampled as 'Yujingxiang', 'Huanghemi', 'Elizabeth', 'Keqibiyu'and 'Yindi'muskmelons (Cucumis melo L.). The disease resistance was screened and partial mechanisms of resistance were studied after inoculated with suspension of Erysiphe cichoracearum.BTH at 100mg/L or harpin at 50mg/L was also sprayed on plants and the study was carried out on induced resistance mechanism and its effect on plant growth and fruit quality. The results showed as below: 1. 'Yujingxiang'and 'Elizabeth'were screened as resistant and susceptible cultivars, respectively. 2. Activity of resistant enzymes had a difference between resistant and susceptible cultivars. POD activity in 'Yujinxiang'was lower than that in 'Elizabeth'. POD activity increased more in 'Yujinxiang'than that in 'Elizabeth'; however, no significant difference was found in PAL and CHT activities of 'Yujinxiang'after inoculation. . Inoculation significantly improved the content of total phenolics and flavonoids . Lignin accumulated more in the leaves of 'Yujigxiang'.. 3. Systemic acquired resistance was induced after treated with BTH or Harpin in the seedlings of 'Yindi'. POD and CHT activities were also increased and lignin accumulated in the leaves. 4. BTH showed better effect than harpin when compared the increase of POD and PAL activities in leaves of 'Yindi'and 'Huanghemi'after treatment. 5. BTH reduced chlorophyll content in leaves,with increase of spraying times. BTH or harpin significantly decreased the single fruit weight. 6. The extracts were obtained with ethanol-dichlormethane from the leaves of melons treated with the elicitors . One zone with antifungal activity was revealed after separation with thin-layer-chromatography (TLC) plates and bioassay identification. The possible antifungal substances were identified with gas chromatography and mass spectroscopy (GC-MS) as bis (2-ethylhexyl) dioctyl ester, 1,2-benzenedicarboxylic, bis (2-methylpr) 1,2-benzenecarboxylic acid, and methyl ester hexadecanoic acid.