The Preliminary Study On Aphid-resistance Mechanism Of Glabrous Cucumber

Aphis gossypii glover (Homoptera:Aphididae) is a serious pest to cucumber in the world.Chemical control is a main technical measure to control the cotton aphids,which causes environmental pollution and increasing resistance of cotton aphids to pesticides. An economic and effective way to control the cotton aphids was planting resistance varieties. However, there are few studies focus on Insect-resistant varieties are one of the economic and effective measures to control the cotton aphids.There are rare researches on the resistance of cucumber to aphid and its mechanism of the cucumber until now. Glabrous cucumber is the mutants of normal cucumber, glabrous cucumber has and was found had the characteristic of ability of aphid-resistance by field observation in field experiment. In this paper, we studied The the mechanism of resistance of glabrous cucumber to cotton aphids in induced resistance aspect with normal and glabrous cucumber as test materials, effects of volatile secondary substances to aphids feeding, and to discuss the correlation between glabrous traits and aphid-resistance. The details main results were as follows:1 Two cucumber varieties were identified and evaluated for resistance to aphid by aphid number ratio method. The results showed that glabrous cucumber was high resistance variety and normal cucumber was high susceptibility variety.2 During the process of invaded stress by aphid, MDA contents of the normal cucumber seedling were higher than glabrous cucumber, and had an upward trend. The activities of SOD, POD, PPO and PAL of glabrous cucumber seedlings were significantly higher than those of normal cucumber seedlings. The activities of SOD, POD and PPO of both materials increased firstly and then decreased, whereas PAL activity increased to maximum and then kept the level. The CAT activity showed the spiral of rising.The lignin and total phenolic contents of glabrous and normal cucumber seedling increased firstly and then decreased, however, the lignin contents increased to the maximum and then kept higher stable level. During the process of invaded stress by aphid, the lignin and total phenolic contents of the glabrous cucumber seedlings were significantly higher than normal cucumber. Therefore, the activities of PAL and PPO, contents of MDA, lignin and total phenol are closed related to the aphid-resistance of cucumber. 3 The soluble sugar, proline and wax contents of glabrous cucumber seedlings were higher than normal cucumber. Soluble sugar contents decreased during the process of invaded stress by aphid, whereas the contents of proline and wax increased. Therefore, proline and wax contents were closed related to the aphid-resistance of cucumber and can be used as physiological indexes for aphid-resistance evaluation.4 The main volatile secondary substances (relative content >1%) between glabrous cucumber seedlings and normal cucumber were same: Ethanol, (E)-2-Decenal,(2E4E)-2,4-Decadienal,Tetradecamethyl-cycloheptasiloxane, Diethyl Phthalate. Aldehydes were the main contents of volatile secondary substances, and its contents in glabrous and normal cucumber seedlings were slightly different. (2E,4E)-2,4-Decadienal was the main volatile secondary substance in the glabrous and normal cucumber seedlings. Ethanol and Diethyl Phthalate formed the specificity of volatile secondary substances of glabrous cucumber seedlings leaves. Acids, Cyclohexenes, Naphthalenes and Furans formed the specific volatile secondary substances of normal cucumber seedlings, which played an important role in invading and feeding, [1,1'-Bicyclopropyl]-2-octanoic acid , 2'-hexyl, methyl ester formed specific volatile secondary substances of glabrous cucumber seedlings, which played an important role in avoiding aphids feeding.