| The paper first studied the resistance of 18 clones of Populus deltoides to larva of Clostera anastomosis. (No.1 to No. 18 represented 95-44, 96-10, 102-14, 104-2, 86-14, 89-2, 89-3, 89-7, 94-30, 81-16, 94-12, 40-1,45-1, 81-22,74-4, 86-98, 86-8, 66-9 clones respectively, 1-72 was chosen as control.) Their mechanisms were also studied. It founded scientific basis for selecting new poplar strains. The main results are as follows:1. Significant difference of resistance in certain clones of Populus deltoids to Clostera anastomosis existed. In both choice and non-choice tests, leaf areas fed by the larvae of Clostera anastomosis were more than that of control in No. 9, 11, 15 clones statistically, but less than that of control in No. 1,2,3,4,6,7, 12,13, 16, 17 clones statistically. There were no significant difference in leaf area feeding between No.10 ,14, 18 clones and that of control. The results above indicated that No. 1, 2, 3, 4, 6, 7, 8, 12,.13, 16, 17 clones are resistant clones and No. 9, 10, 11, 14, 15, 18 clones are susceptive clones.2. Differential effects of certain clones of Populus deltoides on the growth and development existed in larvae of Clostera anastomosis showed in the varies of the main indicators of growth and development, such as larvae weight, weight growth per day and RGR (relative growth rate). No.7 clone, which had higher resistance expressed as amount of leaf feeding, showed inhibitory effects of growth and development on larvae of Clostera anastomosis significantly. However, No.l clone, which had higher susceptivity had positive effect to those significantly.3. Differential effects of certain clones of Populus deltoides on food intakes and feces excretion in larvae of Clostera anastomosis existed. No.7 clone showed inhibitory effects on food intakes and feces excretion on larvae of Clostera anastomosis significantly. However, No.1 clone, which had higher susceptivity had positive effect to those significantly.4. ECI (efficiency of ingested of food) and BCD (efficiency of conversion of digested food) of larvae of Clostera anastomosis after feeding with No. 15 clone increased statistically, it indicated that these kind of clones could promote the growth and development of larva of Clostera anastomosis significantly. However, the two indicators of larvae of Clostera anastomosis after feeding with No.7 clone decreased statistically in the second day, but no significant decrease were observed in the following days, the causes should be studied further.5.In most cases in the study, resistance of the clones tested in Populus deltoides to larva ofClostera anastomosis, expressed as amount of leaf feeding, was statistically and positively related with the content of phenolic compound of their leaves. The only exception was No. 17 clone, in which although the content of phenolic compound of the leaf was lower than that of control, the content of phenolic compound was lower. It implied that other factors effecting the amount of leaf feeding might exist.However resistance of the clones tested was not statistically related with the content of protein and water-soluble carbohydrate in their leaves.6.Most of the resistant clones inhibited the activity of three digest enzymes in larvae of Clostera anastomosis statistically. In most case in the study , the three digest enzymes activity tested in No.9, 11, 15 clones were higher than those of controls. There was only one exception that activity of proteinase in the larvae feeding on leaves of No.9 clone was lower than that of control, but the difference is not significant statistically.7.The activity of superoxide dismutase (SOD) and catalase (CAT) in larvae of Clostera anastomosis was higher than that of control statistically after feeding with resistant clones. However, no distinct effects of No. 9, 11, 15 clones on the activity of the two enzymes, even weak inhibition was showed. Significant relationship between peroxidase (POD) activity in larvae of Clostera anastomosis and certain clones of Populus deltoids did not exist.In...
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