The Change Of Volatile Substance And Soluble Sugar Of Cucumber Infected Aphid And Whitefly

Cucumber is a major vegetable in the world. It has high nutritional value and be cultivated all over China. It is in great demand. Aphid and whitefly are cosmopolitan pests, they prouduce seriouse damage to cucumber production.In the actual production, the glabrous cucumber had repellent effect to whitefly and aphid. In this paper, using glabrous cucumber, glabrate cucumber and normal cucumber as materials, we tested the volatile substance and the content of soluble sugar after inoculated with aphid and whitefly in seedling stage and strain stage, to know the relationship between the resistant-ability to whitefly (aphid) and volatile substance or the content of soluble sugar on cucumber. The results were as follows:1. In aphid (whitefly) selective test, we found that the number of aphids(whitefly) on the glabrous cucumber leaves which cut from the plant was significantly (p<0.05)less than that on narmal cucumber at ten minutes later after initiating the experiment. The number of insects on the glabrous cucumber leaves which were on the plants was significantly (p<0.05) less than that on normal plants at one hour later after initiating the experiment. The number of aphids or whitefly on the glabrate cucumber was more than that on the glabrous cucumber, but it was significantly less than that on the normal cucumber.2. The cucumber materials were inoculated with aphid and whitefly in seedling stage. Compared to the other two kinds of cucumber materials, the glabrous cucumber was not detected the green leafy odors:1-Hexanol and3-Hexenal, which had attractive effect to pests. These odors helped pests to find the food. This was the reason why glabrous cucumber had no attractive effect to aphid and whitefly. Glabrous cucumber was inoculated with aphid and whitefly in strain stage. We did not detected1-Hexnaol, the content of3-Hexenal was reduced, compared with the unvaccinated glabrous cucumber.3. We only detected ocimene which had repellent effect to aphid and whitefly on the glabrous cucumber. In order to verify the function of ocimene, we designed six different concentrations of ocimene solution, and spraying cucumber leaves which were inoculated with aphid and whitefly. Then we checked the number of pests on different kinds of cucumber materials. The results showed that ocimene had repellent effect to aphid and whitefly. Three kinds of cucumber material were improved the resistant-ability to pests.4. We inoculated aphid and whitefly to three kinds of cucumber materials at seedling stage. We found that the content of soluble sugar of glabrous cucumber was very less than that of normal cucumber. The content of souluble sugar of glabrate cucumber was between the normal cucumber and the glabrous cucumber. Soluble sugar was necessary nutrient for pest growth and development. This was the reason why the glabrous cucumber had repellent effect to aphid and whitefly. Ten days later after initiating experiment, the contents of soluble sugar of three kinds of cucumber were reduced. This was the self-protective mechanism of plant.