| In order to illustrate the physiological and biochemical mechanism of the resistance wheat varieties to wheat aphids, a serious pest insect group of wheat in worldwide wheat growing area (mainly Sitobion avenae(F.) (SA) and Rhopalosz hum padi (L.) (RP) in China), and explore the function of G protein (guanine triphosphate binding protein) in signal transduction between wheat aphids and outside surroundings, a chemically defined diet capable of the normal development of wheat aphids in their several successive generations was created, and a series of methods for testing the action processes of G protein in signal transduction these aphids involved were developed. Based on these preparation, the resistance mechanism of secondary metabolites and water /alcohol soluble proteins of wheat to wheat aphids, and the expression, separation, purification and activity measuring of G protein and its coupled components were analysed and determined, as well as its actions in signal transduction pathway were deduced. The major advancements were as follows: 1 Based on the diet of Auclair (1965), a diet was developed by systemic analysis the nutrition of wheat plant and several trials and modification. In the diet, the optimal pH value was 6.0; the optimal sucrose concentration for SA and RP were 25% and 30%, respectively. The component of diet was determined by feeding aphids on the diet which one of L-amino acids or vitamins was omitted. The result showed that: for SA, nine amino acids, for example Arginine, Cysteine, Histidine, and eight vitamins, for example Ascorbic acid and Biotin were necessary nutrition; another six amino acids and two vitamins (Calcium patothenate, lnositol) were non-necessary nutrition; the other seven amino acids and riboflavin were deleterious ones; For RP: there were 5 necessary amino acids, such as Histidine, Arginine and Glutamine, etc.; 3 non-necessary ones, such as Cysteine, Cysteine and Proline, and 9 deleterious ones. Feeding on the diet without the deleterious components, the survival rate, duration and larviposition of SA had no significant difference from the susceptible wheat plant. SA could be sustained on the diet for 2-3 generations, which was better than all the published wheat aphids diets. RP were less successfully sustained on the diet, Artificial diet for RP need further study.2 By adding different dosage of purified chemicals of wheat secondary metabolites: tannic acid, gallic acid, coumarin, DIMBOA, MBOA, catechin, rutin, quercetin in artificial diet of wheat aphids, the effects on the two species of wheat aphid were determined by using their life parameters such as survival, growth, development and nymphal weight gain; and the combination effects of four kinds of secondary substances on SA were studied. The results showed that all test secondary substances but rutin with a different degree resistance to wheat aphids. The resistant thresholds of these secondary substances were suggested by further statistical analysis with above life parameters. There was significantly positive interaction between tannic acid and gallic acid (total phenolic compounds) to inhibit SA survival, and to some degree of positive interaction between tannic acid and MBOA, and negative interaction between gallic acid arid DIMBOA. The results showed that tannic acid, total phenolic compounds and couniarin are important secondary chemicals in resistance to SA. Tannic acid, catechin, coumarin and MBOA are major secondary chemicals in resistance to RP. 3 The effects of the different resistant wheat varieties on aphid feeding behavior were...
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