| Azalea is one of the most famous ornamental flowers in the world,and in recent years it is also more widely used for garden plants in sichuan province.Stephanitis pyrioides Scott is one of the most important pests,which seriously affects the ornamental value of azaleas.At present,chemical control is the main method of prevention and control to the pest.But overused or misused pesticides can lead to a range of problems,such as environmental pollution,degradation of quality and emergence of drug resistance.Therefore,breeding and utilizing insect-resistant varieties is the most recognizable and effective management strategy.But until now,researches on insect resistance were relatively rare.In this thesis,chosing Rhododendron radendum Fang,Rhododendron indicum(L.)Sweet,Rhododendron obtusum(Lindl.)Planch,Rhododendron hybridum Hort as the host plants,the selectivity and adaptability of S.pyrioides and the mechanism of azalea resistance to S.pyrioides were studied in order to provide a theoretical basis for the screening and application of insect resistant Rhododendron.The results were as follows:1?S.pyrioides finished generation development and breed on R.indicum,R.obtusum and R.hybridum,but failed on R.radendum.The feeding and spawning selectivity of S.pyrioides on 4 kinds of commonly azalea were studied by the distance free choice means.The results showed that the selection levels decreased in R.indicum,R.radendum,R.obtusum,R.hybridum at the beginning of feeding.After feeding basically stable,the selection tropism decreased in R.hybridum,R.indicum,R.radendum,R.obtusum,while the spawning tropism of R.hybridum,R.indicum,R.obtusum,R.radendum.To sum up,S.pyrioides was more suitable for growth and reproduction on R.indicum and R.hybridum.2?There were significant difference in physical traits of four azaleas(P < 0.05).Analyses of the correlation between the feeding selection of S.pyrioides and the leaf physical characteristics showed that leaf area,thickness,leaf width ratio,leaf front hair density,wax content had no significant correlation with the host selection of S.pyrioides at the beginning of feeding,and there was significantly positive correlation between leaf back hair density,vascular bundle depth and the host selection,the correlation coefficients were 0.665(P = 0.001)and 0.469(P = 0.037).A significantly negative correlation existed between the feeding selection and the content of chlorophyll(R =-0.767,P = 0).However,after feeding stability the selection had no significant correlation with leaf area,thickness,wax content,leaf back hair density.There was significantly positive correlation between the host selection and the contentof chlorophyll,vascular bundle depth,the correlation coefficients were 0.486(P = 0.03)and 0.584(P = 0.007).But the selection had a significantly negative correlation with leaf width ratio and leaf front hair density,the correlation coefficients were-0.602(P =0.005)and-0.688(P = 0.001).These results showed that the content of chlorophyll and leaf hair density were the most critical factors influencing insect-selectance.However,the spawning results was also analyzed that there was significantly negatively correlated with leaf width,leaf front hair density and wax content,the correlation coefficients were-0.818(P = 0),-0.761(P = 0)and-0.695(P = 0.001),but had a significantly positive correlation with the content of chlorophyll(R = 0.588,P = 0.006).Therefore,all results suggested that the most critical factors were leaf width ratio,leaf front hair density and wax content in the spawning selection of S.pyrioides.3?There were significant difference in nutriments of four azaleas(P < 0.05).There was no significant correlation between the content of soluble protein,soluble sugar,free amino acid and the host selection at the beginning of feeding,but free proline was positively correlated with the host selection(R = 0.561,P = 0.01).However,After feeding stability there was significantly negative correlation between the content of soluble protein,soluble sugar and the host selection,the correlation coefficients were-0.73(P = 0)and-0.881(P = 0).A significantly positive correlation existed between the content of FAA,Pro and the selection,the correlation coefficients were 0.762(P = 0)and 0.554(P = 0.011).The relationships between spawning selection of S.pyrioides and leaf nutriments showed that the selection had no significant correlation with SP,but had a significantly negative correlation with SS(R =-0.797,P = 0).However,FAA and Pro were significantly positive correlation with the ovipositivity of S.pyrioides,the correlation coefficients were 0.891(P = 0)and 0.611(P = 0.004).Therefore,these nutriments could be used as the insect-resistance factors of azalea.4?The correlation between the content change of secondary metabolites and the host selection of S.pyrioides was analyzed by different azaleas.The results showed that there were different levels,which was significantly different(P < 0.05).A significant negative correlation existed between the feeding and spawning selection of S.pyrioides and the content changes of total phenols and tannin,the correlation coefficients were-0.819(P = 0),-0.62(P = 0.004)and-0.763(P = 0),-0.605(P = 0.005).But there was significantly positively correlated with the content changes of MDA,and correlation coefficients were 0.704(P = 0.001)and 0.704(P = 0.001).therefore,all results showed that the insect-resistance of azalea was positively correlated with the content changes oftotal phenol and tannin,but had a negative correlation with the content changes of MDA.5?It was studied that there were significant difference in leaf enzymatic activity of four azaleas(P < 0.05).The relationships between host selection of S.pyrioides and lenzymatic activity showed that the activity increase of POD,SOD were significantly negatively correlated with the feeding and spawning preferences,the correlation coefficients were-0.819(P = 0),-0.62(P = 0.004)and-0.763(P = 0),-0.605(P =0.005).Before and after feeding,the activity ratio of CAT was significantly negative correlation with the feeding and spawning selection,the correlation coefficient was-0.803(P = 0)and-0.572(P = 0.008).All results showed that insect-resistance of azalea was significantly positively correlated with the activity changes of POD and SOD,and was negatively correlated with the activity decrease of CAT. |
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