Effects Of Waxy Surface On The Feeding Behavior Of Aphids In Cotton Leaves

Feeding is one of the most important relationships between the plant and pests, and leaf is the interface of interactions. Therefore, leaf physical-chemical characteristics will affect the insects feeding behaviors. The epidermal waxes, lipophilic compounds, cover the surface of a plant as the boundary between the plant tissues and the environment.To explore the mechanisms of the influence of epidermal waxes on the herbivore insects, we tested the aphid feeding behaviors on two cotton lines (ZM16 and ZM30), analyzed the contents of epidermal waxes and their effects on the performances of cotton aphids.With the electrical penetration graph (EPG) technique, feeding behaviors of cotton aphids on the ZM16 and ZM30 were researched. The results show that there were significant differences between the seven feeding performances of cotton aphids on the two cotton lines. Cotton aphids took longer time to find the puncture spot (the duration of NP in period I:ZM 16>ZM 30, P=0.006<0.01); Cotton aphids punctured more hardly in ZM 16 (the duration of punctuation in period I:ZM 16>ZM 30, P=0.0170.05); Cotton aphids had a longer time to get to the phloem (Time to 1st E:ZM 16>ZM 30, P=0.017<0.05); Aphids penetrated more frequently to mesophyll and had a longer time on the first penetration in ZM 16 (Ratio of probes in period I/total number of probes, Duration of 1st SI:ZM 16>ZM 30, P=0.030,0.044<0.05); Meanwhile, Aphids were easier to replace feeding sites in ZM30(the number of E after the 1st SI, Number of SI:ZM 16<ZM 30, P=0.028,0.023<0.05).The differences from the EPG results could be located the factors existing on the leaf surface. Therefore, the epidermal wax contents were extracted and analyzed with gas chromatography (GC). It was found that there was no significant difference between total content of the epidermal wax and the performances; But there was significant correlation between some epidermal wax compositions and the EPG parameters of cotton aphids. The relationships between the wax contents and the feeding behaviors of cotton aphid were established with the linear regression method. And some wax compositions such as W14、W15、W18 affected a variety of cotton aphid feeding behaviors via their content, others may affected the feeding behaviors by the combined effect.