Study Of Selection Mechanism On Oviposition Host Of Citrus Psylla(diaphorina Citri Kuwayama)

The Asian citrus psyllid,Diaphorina citri Kuwayama(Hemiptera:psyllidae)is the most important pest of citrus plants worldwide.The species is also the major vector of Citrus huanglongbing,which is one of severe quarantine diseases both in aborad and domestic.In order to determine the suitability of host plant and select specific oviposition site,the phytophagous insects determine the physical and chemical characteristics of host plants by mainly using the sensillas of ovipositor and female tarsi after settling on the host plants.The influencing factors of the whole deterministic process of host plants is mainly determined by the nutritional status of the host plant,the oviposition stimulating pheromone and the learning experience in the process of insects growth.In this paper,it is the starting point that how ACP adult female select the spawning suitability of host plants,and it is the aim to study the effects of host plant nutrient status,oviposition stimulats and the sensillas of female ovipositor on the selecting oviposition host plant of ACP adult female.We analysis the component of major nutrients from six common host of the ACP,including Murraya exotica L,Citrus sinensis(L.)Osbeck,C itrus maxima,Citrus reticulate,citrus reticulata Blanco,Citrus Limon(L)and the correlation with the fecundity of ACP adults female in various plants.In order to find the bioactive substances of affecting the oviposition of ACP adult,we analysis the effect of surface extract of 6 kinds of host plants on the oviposition of ACP adults,and we also analysis the specific components of the host plants surface compounds by gas chromatography mass spectrometry.We also determined the ultrastructure of sensillas on genitalia of the ACP adults female by scanning electron microscope.And we analysis the function of the various sensillas,we also determined the effects of sensillas on the oviposition of ACP adult by using concentrated acid to shielde the sensillas.The main results of this paper were as follows:(1)Under nonselective conditions,We determined the fecundity of ACP adults female on 6 common host plants—Murraya exotica L,Citrus sinensis(L.)Osbeck,Citrus maxima,Citrus reticulate,citrus reticulata Blanco,C itrus Limon(L).The results show that there was significant differences of the fecundity of ACP adults female between the 6 kinds of host plants.The marshalling sequence of the fecundity of ACP female adults was Murraya exotica L > Citrus sinensis(L.)Osbeck > Citrus maxima > Citrus reticulate > citrus reticulata Blanco>Citrus limon Eureka(L).(2)We determined the main nutrients of shoots of host plant,including soluble sugar,soluble protein,moisture content and chlorophyll content.Meanwhile,we also determined the type and content o f free amino acids in shoots,and analyzed the correlation between nutrient substance content and fecundity of ACP female adults.The results showed that there were significant differences in the contents of chemical components among the six host plants.The results of correlation analysis showed that there was significantly positive correlation between the fecundity of ACP female adults on six host plants with soluble protein and chlorophyll content of six host plants.There was a certain correlation between the fecundity of female adults citrus Psylla on six host plants with the soluble sugar content and water content,but the correlation was not abvious.There was full range free amino acids six species of host plants.The marshalling sequence of total amino acid(TAA)content was Citrus sinensis L>Citrus maxima>Murraya exotica L>Citrus reticulate>citrus reticulata Blanco>Citrus limon Eureka(L).And there was significantly positive correlation between the fecundity of ACP female adult on six host plants with eight kinds of essential amino acids(EAA)content.(3)We extracted the surface compounds of six host plant shoots by the method of methanol soaking,and we determined the inductivity of the surface compounds of six host plant shoots to ACP adults by using four armolfactometer;meanwhile,we analyzed the effect of surface compounds of young shoots on the fecundity of ACP adult female.The results show that there had a significant inductivity of five host plants Citrus sinensis L?Citrus maxima?Murraya exotica L?Citrus reticulate?Citrus limon Eureka(L))shoot surface compounds to ACP adult female,and the inductivity of Citrus maxima and Murraya exotica L is the strongest.Under selective and non selective conditions,the effects of host shoot extracts on oviposition of ACP adults were determined.We found that the extracts of several host shoots had oviposition stimulating effect on ACP adults,and the oviposition stimulating rate of each extracts was significantly correlated with the amount of oviposition on each host.It was explain that the extracts of host shoot plays an important role in selection and judgment of the host of ACP adults.(4)We analyzed the shoot specific components of the surface compounds of Murraya exotica L,Citrus sinensis L,Citrus maxima,Citrus reticulate,citrus reticulata Blanco,Citrus limon Eureka(L)by using the GC-MS analysis technology.The results showed that the surface compounds of six host plants shoots mainly contain fatty alcohols,carboxylic acids,esters,alkenes,esters?aldehydes and other compounds.Fatty alcohols and alkenes of the surface compounds of six host plant shoots were higher in terms of the identified compounds.(5)We determined the type,morphology and distribution characteristic of the sensillas on genitalia of ACP female adult by using scanning electron microscopy(SEM)technique.The results showed that there were trichoid sensilla,chaetica sensilla and basiconica sensilla distributing on the genitalias of ACP adult female.And the trichoid se nsillas were distributed on the external genitalia,the sensilla chaetica were mainly distributed on the end of the back plate,the sensilla basiconica were mainly distributed on the end of the back plate and the base of the sternum.According to the surface structure and type of sensilla,it is recommended that these sensilla are contact receptors,which are mainly used to sense and judge the physical characteristics of the host surface as well as oviposition stimulating.