The Research On The Physiological Mechanism Of Glabrous Cucumber Resistance To Aphid

Aphid has many varieties. It is the major pests on cucumber in most cucumber-producingareas of the world. It not only influences plant development, but also spreads virosis. With therapid development of modern agricultural facilities, the area of cucumber cultivation expandsrapidly. The effects of cucumber facing pest hazard are also increase sharply, particularlycotton aphid have become increasingly prominent. For a long time, people relied on pesticidesto control pests, not only polluted the environment, but also easily led to aphid resistance,increased prevention cost. Use of insect-resistant varieties to resist insect damage caneffectively reduce the possibility of air, water and soil pollution, reduce pesticide residues invegetable products, with significant economic, social and ecological benefits. So selectinginsect-resistant cucumber varieties is the fundamental strategy for pest control. In the practiceof cultivation, glabrous cucumber has obvious resistance to aphid. To investigate thephysiological mechanism of the aphid-resistance of cucumber, a normal cucumber cultivar(which is susceptible to aphid), a glabrous cucumber (which has aphid-resist ability) and aglabrate mutant were infested thirty aphids in the same generations. We determinated majornutritional materials, secondary metabolic enzyme and secondary metabolic metabolites in theleaf of cucumber infested by aphids. We also observed the microstructure and ultrastructureof three kinds of cucumber. The main results of the study were listed as the following：1. The glabrous character cannot be expected to impart total resistance to aphid, however,the suppression it provides will result in more manage-able numbers. If glabrous cucumbervarieties were used in conjunction with chemical materials, the number of surviving aphidswould be below the damaging level. Use of glabrous cucumber with the resultant decrease inaphid amount could delay the need for insecticides and might permit other biological factorsto be utilized more effectively.2. It was difficult for adult aphids to lay larva on glabrous leaf surface. Due to the lack oftrichome protection, aphids on the glabrous cucumber leaves were more likely to be found bypredators. These could be the reasons for glabrous cucumber to resistant aphid.3. The thickness of leaf, palisade tissue, spongy tissue, epidermis of glabrous cucumberwere greater than those of normal cucumber, which reached a significant level.The morethickness of leaf tissue will increase physical barriers to aphid feeding, development andreproduction, and slow aphid population increase.4. The glabrous cucumber has lower content of water, soluble sugar and free amino acid.The content of soluble protein is in a low level firstly and then rise. Lower content of Chlorophyll in the leaf of glabrous cucumber is one of the leading causes of glabrouscucumber leaf deficient enough nutrient materials. The relative change in the content of thesesubstances, or lack of some kinds of nutrients or with a disproportionate amount, will affectthe normal development of the pests, directly affecting the growth and reproduction of theinsect, so that the host itself obtained insect resistance by reducing the survival rate of thepest.5.The content of SOD、POD、APX、MDA in the leaf of three kinds of cucumber areshowing the same trend of growth, reduction and growth again, which showing somerelationship with the aphid population growth, indicating that these secondary metabolicenzyme activity changes are associated with cucumber resistance. And the contents of SOD,POD, APX of glabrous cucumber were higher than that of normal cucumber, or faster thannormal cucumber. The higher enzyme activity or faster growth enzyme activity is one of thereasons for glabrous cucumber to resistant aphid.6. Compared with the normal, glabrous cucumber had higher content of flavonoids,tannins and other secondary substances, these secondary metabolites can affect insectbehavior and metabolism, make the aphids repellent or anti-feedant, destruct normalmetabolism of insects, more serious can cause insects to poisoning or even death. The highsecondary metabolites is one of the causes for glabrous cucumber to resistant insect.