Developmental Performance And Oviposition Preference Of Rice Leaf Folder On Rice And Corn

The rice leaf folder(RLF),Cnaphalocrocis medinalis,is variously distributed in rice planting area of China,which is a serious threat to rice production.C.medinalis.mainly damage rice in nature,but it can also forage graminaceous plants such as corn,wheat and setaria.This thesis established the age-stage two-sex life tables to determine the influence of host switch on the performance of host populations of C.medinalis to explore the host effects of rice and corn.The mechanism of physiologic and chemical ecology of C.medinalis host preference was researched by qualitative and quantitative analysis of volatiles of rice and corn and electrophysiological active components.The main results are as follows:1.Effects of host switch on the performance and life-table parameters of host populations of C.medinalisThe C.medinalis.corn population(RLF-cp)and rice population(RLF-rp)were fed with their original and switched host plants,respectively,resulting in four treatment combinations: RLF-cp feeding on corn,RLF-cp feeding on rice,RLF-rp feeding on corn and RLF-rp feeding on rice.The age-stage twosex life tables of the four treatment combinations were established,and the performance and life table parameters of these C.medinalis.host populations were measured.The developmental duration of immature stage of RLF-rp feeding on rice was the longest(29.2 d),while that of RLF-cp feeding on rice was the shortest(24.8 d).The values of performance indexes(pupal weight,pupation rate,emergence rate,and fecundity),life table parameters(survival rate,maximum fecundity,maximum reproductive value,immature life expectancy),and population parameters(intrinsic rate of increase,finite rate of increase,and net reproductive rate)of RLF-cp and RLF-rp feeding on corn were the highest while those of RLF-cp feeding on rice were the lowest(except for pupal weight),and those of RLF-rp feeding on corn were higher than those of RLF-rp feeding on rice.Performance and population growth of the corn population of C.medinalis decrease significantly after host switch,while those of the rice population increase slightly,indicating that corn is more suitable for improving performance and population growth of C.medinalis than rice.2.Oviposition preference of C.medinalis and volatiles collection and identificationThe oviposition preference of RLF-cp and RLF-rp to rice and corn was tested in cages,indicated that C.medinalis preferred to lay eggs on rice.51 volatiles of rice at tillering stage and maize at seedling stage were collected by dynamic headspace sampling,then were separated and identified by gas chromatography-mass spectrometry(GC-MS).43 and 36 volatiles components of rice and corn were detected,respectively,among which 28 components were shared in corn and rice,15 and 8 components were specific to corn and rice,respectively.There were more green leaf volatiles(GLVs)and terpenoids in rice volatiles,and the content of corn volatiles is more than rice.3.Electrophysiological responses and selecting behavior of C.medinalis to volatiles of rice and cornC.medinalis preferred rice volatiles and lost the ability of volatiles selection after antenna excised.Active components were separated and identified by gas chromatography-electroantennographic detection(GC-EAD),there were 14 active components in volatiles of rice and corn,which belonged to green leaf volatiles,terpenoids,aliphatic compounds and aromatic compounds.Among the active components,7 components were shared in corn and rice,5 and 2 components were specific to rice and corn,respectively.EAG response was tested by the gradient concentration solution of standard compounds of active volatiles at 0.1-100 μg/μl,showed that the EAG values to most active volatile components increased with increasing concentration but were saturated at certain concentrations in some components.Aldehydes(nonanal,decanal),ktones(2-heptanone),green leaf volatiles(3-hexanol,(E)-2-hexenal,(E)-2-hexen-1-ol,cis-3-hexenyl-1-acetate)elicited strong EAG responses.The olfactory selection showed that 3-hexanol,(E)-2-hexenal,cis-3-hexenyl-1-acetate,4-ethylbenzaldehyde,benzothiazole was significantly attractive while decanal,nonanal,2-heptanone was significantly repellent to C.medinalis,DL-Limonene,Benzaldehyde,Acetophenone,Mesitylene had no behavioral activity.EAG responses and behavioral reaction to volatiles blends showed that the EAG responses and tendency of C.medinalis to rice volatile blends was stronger than that of corn volatile blends,and the volatile substances shared in rice and corn enhanced the reaction.