The life-history trait trade-offs mediated by reproduction and immunity in the brown planthopper,Nilaparvata lugens Stål

Reproduction and immune defense are costly functions,and they are expected to tradeoff with each other to drive evolution.The brown planthopper(BPH),Nilaparvata lugens Stål(Hemiptera,Delphacidae),is a global superpest that mostly damages rice crops.Yeast-like symbionts(YLS)exist in the abdominal fat body tissue and are tightly associated with the development,growth,and reproduction of BPH.Our previous research demonstrated that mating behavior promotes the release of YLS from the fat body into the hemolymph in the BPH,thereby triggering an immune response.Additionally,the fitness costs related to life-history traits of BPH(such as survival rate)have a strong dependence on the relative abundance of YLS.However,the possible relationship between reproduction and the immune response in BPH has not been identified.In this study,an omics-based approach was used to analyze the transcriptome of fat body tissues in mated and unmated BPH at 72 h post-eclosion,from which two antimicrobial peptide genes,NlDefensin A(NlDfA)and NlDefensin B(NlDfB),were selected since they were highly expressed in mated BPH.Subsequently,the full-length cDNA sequences of the NlDfA and NlDfB genes were cloned and analyzed.qPCR results showed up-regulation of the NlDfA and NlDfB genes in mated BPH when compared to unmated BPH.Spatial-temporal expression analysis indicated that the NlDfA and NlDfB genes were expressed in all tissues and developmental stages,and they were most highly expressed in the fat body at 24 h post-eclosion.Moreover,the symbionts in BPH were significantly inhibited by the in vitro expression of the NlDfA and NlDfB proteins.Furthermore,RNA interference(RNAi)-mediated suppression of NlDfA and NlDfB dramatically increased the relative abundance of YLS in the fat body,while YLS in the hemolymph decreased significantly.These BPHs also displayed some fitness disadvantages in survival,fecundity,hatchability,and possibly the vertical transmission of YLS from hemolymph to egg.Our results indicated that mating could heighten the immunity of BPH by upregulating the expression of the NlDfA and NlDfB genes,which protect the host from pathogen challenges during reproduction.However,the reduced content of YLS may act as a fitness disadvantage in dictating the life-history traits of BPH.This work has significant theoretical and practical implications for the precise green control technology that involves crucial gene targeting,as well as for the“endosymbionts for pest control”strategy in insects.

稻虱缨小蜂(Anagrus nilaparvatae)在两种稻飞虱上的生殖力及其应用潜能

利用寄生变红卵和仔代成蜂数量作为繁殖力估计等方法,编制了稻虱缨小蜂(Anagrus nilaparvataepang and wang)在褐飞虱(Nilaparvata lugens(Stal))卵和白背飞虱(Sogatella furcifera(Horvath))卵上繁殖的实验种群生命表,测定了稻虱缨小蜂寄生褐飞虱和白背飞虱的生殖力,分析了稻虱缨小蜂对稻飞虱卵的寄生能力。结果表明:在相同的繁蜂条件下,稻虱缨小蜂寄生褐飞虱卵的净生殖力R0为10.26,内禀增长率rm为0.2213,平均单雌产仔数为14.52头;寄生白背飞虱卵的净生殖力R0为8.78,内禀增长率rm为0.1840,平均单雌产仔数为12.20头。两组生命表参数比较分析显示褐飞虱卵具有较强的室内繁蜂潜能,可利用其进行室内繁蜂。应用稻虱缨小蜂、褐飞虱及白背飞虱的生命表参数讨论了稻虱缨小蜂在稻飞虱生物防治中的应用潜能及其可能的利用途径。

褐飞虱Nilaparvata lugens(S"非汉字符号"l)肌动蛋白基因3′-RACE及基因表达的RT-PCR检测

通过锚定的 3′ RACE筛选实验 ,确定锚定效率最好的下游引物 ,用于褐飞虱各发育期肌动蛋白基因表达的RT PCR检测。结果表明 :3个锚定引物中 ,0 4 2 2 7( 5′ >TCACACAGGAAACAGCTATGACTTTTTTTTTTTTTTA <3′)的锚定效率最好 ,可以扩增出 5条褐飞虱的肌动蛋白基因 3′末端片段 ,依其大小命名为BPH A、BPH B、BPH C、BPH D、BPH E。RT PCR检测表明 :BPH A从 3龄开始到成虫期都有常量表达 ;BPH B、BPH C、BPH E从 2龄开始到成虫期都有表达 ;BPH D在整个幼虫期都有表达 。

Impact Evaluation of Insect-Resistant Transgenic Rice on the Feeding and Oviposition Behavior of Its Non-Target Insect, the Brown Planthopper, Nilaparvata lugens (Homptera: Delphacidae)

The feeding and oviposition behavior of the brown planthopper (BPH), Nilaparvata lugens on two transgenic indica rice homogenous genotypes (B1 and B6) with cry1Ab gene from Bacillus thuringiensis and transgenic restored line of hybrid rice (MSA) with SCK gene (a modified CpTI gene) were measured, compared with those on their corresponding non transgenic parental cultivars Jiazao935 and Minghui86 performed by BPH. Under the selection condition of host plants by BPH, loading percentage, oviposition preference and laying egg number of BPH both on transgenic cry1Ab rice and transgenic SCK rice were not significantly different from those on their controls, while their total number of probing wound caused by PBH expect for feeding on B1 plants was markedly more than that on the control. In contrast, under the non selection condition, total number of probing wound caused by BPH on either transgenic cry1Ab rice or transgenic SCK rice was pronouncedly more than those on their controls. Conversely, their honeydew amount excreted by BPH after feeding for 24 h was significantly less than those on the control. As a conclusion, three tested transgenic rice genotypes with insect resistance acted adverse effect on BHP feeding, and no marked effect on BPH oviposition.

Effects of Temperature on Functional Response of Anagrus nilaparvatae Pang et Wang (Hymenoptera:Mymaridae) on the Eggs of Whitebacked Planthopper,Sogatella furcifera Horvth and Brown Planthopper,Nilaparvata lugens Stl

Understanding the temperature affecting parasitic efficiency is critical to succeed in utilizing parasitoid as natural enemy in pest management. Laboratory studies were carried out to determine the effects of temperature on parasitoid preference of female Anagrus nilaparvatae Pang et Wang （Hymenoptera：Mymaridae） to the eggs of whitebacked planthopper （WBPH）, Sogatella furcifera Horváth and brown planthopper （BPH）, Nilaparvata lugens Stl to build a composite model describing changes in parasitic response along a temperature gradient （18, 22, 26, 30, 34°C）. The results showed that attack responses of A. nilaparvatae on WBPH and BPH were the best described by a Type II functional response. The two parameters, attack rates （a） and handling times （Th）, of A. nilaparvatae to both eggs were influenced by the temperature. The maximum attack rates to WBPH （1.235） and BPH （1.049） were at 26 and 34°C, respectively, and the shortest handling times to WBPH （0.063） and BPH （0.057） were at 30 and 26°C, respectively. However, the optimal temperature for parasitic efficiency of A. nilaparvatae to WBPH and BPH eggs was both at 26°C, which showed that the present microclimate temperature of the habitat in the paddyfield was beneficial to A. nilaparvatae and indicated that parasitic efficiency of A. nilaparvatae would be impaired by global warming.

Effects of Pesticide Applications on the Biochemical Properties of Transgenic cry 2A Rice and the Life History Parameters of Nilaparvata lugens Stl (Homptera: Delphacidae)

Effects of transgenic Bt rice on non-target pests following pesticide applications plays an important role in evaluating the ecological safety of transgenic rice. Changes of the life history parameters of laboratory population of Nilaparvata lugens feeding on transgenic Bt rice T2A-1 and its parental line cv. MH63 as the control, and the contents of oxalic acid and soluble sugar following three pesticides （triazophos, jinggangmycin and chlorantraniliprole） treatments were investigated in this paper. Results showed that the population parameters of N. lugens and the physiological and biochemical parameters of rice did not differ significantly between T2A-1 and MH63 without pesticide application. But, the emergence rate （ER）, the nymphal number of next generation （NN）, and the index of population trend （IP） on T2A-1 treated with 10 mg L^-1 of triazophos were significantly higher than those on MH63, respectively, while the hatchability （HB） on T2A-1 treated with the three pesticides were obviously lower than those on MH 63. Furthermore, the content of oxalic acid in MH63 treated with 20 mg L-1 triazophos and, 40 and 80 mg L-1 chlorantraniliprole was significantly higher than that in T2A-1, while the content of soluble sugar in T2A-1 treated with 400 mg L-1 jinggangmycin was significantly higher than that in MH63. The results above indicated that triazophos in a low dose could cause a more favor of T2A-1 to population growth of N. lugens compared with MH 63.

Susceptibility of Different Populations of Nilaparvata lugens from Major Rice Growing Areas of Karnataka, India to Different Groups of Insecticides

Susceptibility to insecticides was investigated by collecting field populations of brown planthopper from different locations of southern Karnataka, India （Gangavati, Kathalagere, Kollegala, Soraba and Mandya）. All the field populations differed in their susceptibility to insecticides. In general, Soraba and Mandya populations were more susceptible to insecticides compared to Gangavati and Kathalagere populations. The resistance ratios varied greatly among the populations viz., chlorpyriphos （1.13- to 16.82-fold）, imidacloprid （0.53- to 13.50-fold）, acephate （1.34- to 5.32-fold）, fipronil （1.13- to 4.06-fold）, thiamethoxam （1.01- to 2.19-fold）, clothianidin （1.92- to 4.86-fold）, dinotefuran （0.82- to 2.22- fold）, buprofezin （1.06- to 5.43-fold） and carbofuran （0.41- to 2.17-fold）. The populations from Gangavati Kathalagere and Kollegala exhibited higher resistance to some of the old insecticides and low resistance to new molecules.

Interactive Effects of Elevated CO_2 and Temperature on Rice Planthopper, Nilaparvata lugens

It is predicted that the current atmospheric CO2 concentration will be doubled and global mean temperature will increase by 1.5-6＆#176;C by the end of this century. Although a number of studies have addressed the separate effects of CO2 and temperature on plant-insect interactions, few have concerned with their combined impacts. In the current study, a factorial experiment was carried out to examine the effect of a doubling CO2 concentration and a 3℃ temperature increase on a complete generation of the brown planthopper （Nilaparvata lugens） on rice （Oryza sativa）. Both elevated CO2 and temperature increased rice stem height and biomass of stem parts. Leaf chlorophyll content increased under elevated CO2, but only in ambient temperature treatment. Water content of stem parts was reduced under elevated temperature, but only when coupled with elevated CO2. Elevated CO2 alone increased biomass of root and elevated temperature alone enhanced leaf area and reduced ratio of root to stem parts. Brown planthopper （BPH） nymphal development was accelerated, and weight of and honeydew excretion by the F1 adults was reduced under elevated temperature only. Longevity of brachypterous females was affected by a signiifcant interaction between CO2 and temperature. At elevated temperature, CO2 had no effect on female longevity, but at ambient temperature, the females lived shorter under elevated CO2. Female fecundity was higher at elevated than at ambient temperature and higher at elevated CO2 than at ambient CO2. These results indicate that the combined effects of elevated temperature and CO2 may enhance the brown planthopper population size.

High Temperature Modifies Resistance Performances of Rice Varieties to Brown Planthopper,Nilaparvata lugens(Stl)

To investigate the effect of temperature on the resistance characteristics of dce varieties with different resistance genes to brown planthopper （BPH）, Nilaparvata lugens （Stal）, the resistances of IR26 （Bphl） and IR36 （bph2） to BPH population in Hangzhou, China were monitored in greenhouse during September in 2007 and 2008 by using the standard seedling screening techniques （SSST） developed by the International Rice Research Institute （IRRI）. Furthermore, the changes in resistance of IR26 and IR36 to BPH, soluble sugar and oxalic acid contents in 25-day-old rice plants of susceptible variety TN1 and resistant varieties IR26 and IR36 were detected at five temperatures （22℃, 25℃, 28℃, 31℃ and 34℃）. IR26 completely lost resistance both in greenhouse and at the five tested temperatures. IR36 still had moderate resistance at natural temperature, but its resistance decreased gradually when the temperature increased from 25℃ to 34℃, and fully lost its resistance at 31℃ and 34℃. The highest durable resistance of IR26 and IR36 were recorded at 25℃. The soluble sugar content in plants of the three tested rice varieties increased with temperature increase, and the oxalic acid content increased with the temperature increase at first, maximized at 25℃, and then declined. Two-way ANOVA indicated significant effects of temperature and rice variety on contents of soluble sugar and oxalic acid in rice plants

Selection of Reference Genes for Gene Expression Analysis in Nilaparvata lugens with Different Levels of Virulence on Rice by Quantitative Real-Time PCR

The brown planthopper Nilaparvata lugens Stal （Homoptera： Delphacidae） can cause hopperburn by feeding on rice and also can transmit the grassy stunt disease. Resistant rice varieties have been developed, but several N. lugens strains can recover their virulence to these resistant rice varieties. In the present study, reference genes with stable expression levels in N. lugens populations showed different levels of virulence to susceptible and resistant rice varieties. The expression of six candidate reference genes in N. lugens feeding on susceptible and resistant rice varieties was analyzed. These genes were evaluated for their potential use in the analysis of differential gene expression. Polymerase chain reaction data was generated from N. lugens, including two different treatments （resistant or susceptible rice） and three virulent N. lugens populations. Three software programs （BestKeeper, Normfinder and geNorm） were used to assess the candidate reference genes. Both geNorm and Normfinder identified the genes 18S, E-ACT, E-TUB and a-TUB as the most stable reference genes. BestKeeper identified ETIF1 as the optimal reference gene with the least overall variation, whereas 18S and a-TUB were the second and third most stably expressed genes, respectively. Therefore, we concluded that the genes 18S and a-TUB were the most suitable reference genes in N. lugens. These results will facilitate future transcript profiling studies on N. lugens populations that show variation in virulence levels on different rice varieties.

Comparative analysis of the ecological fitness and transcriptome between two genotypes of the brown planthopper Nilaparvata lugens

Insect quantity is an important index for determining the degree of damage to plants.The brown planthopper(BPH),Nilaparvata lugens(Stal),is one of the most important rice pests in Asia.Here,we used two genotypes of BPH,a highfecundity genotype(HFG)and a low-fecundity genotype(LFG),to measure their ecological fitness and to explore possible causes for genotype differentiation by transcriptome sequencing.Our results showed that there were significant differences in body weight,egg hatching rate and honeydew secretion between the HFG and LFG,particularly,the number of eggs laid per female was more significant.Transcriptional analysis showed that a total of 1966 differentially expressed genes(DEGs)were mainly involved in energy metabolism,carbohydrate and lipid syn thesis,in sect horm one syn thesis and fecun dity-related pathways.Moreover,we found that the phosphorylation levels of AMPK,AKT and FoxO and the synthesis of ecdysone were different between the two genotypes of BPH.These findings may partially explain the differenee in the ecological fitness between HFG and LFG.This study is the first to compare the differences between two genotypes of BPH and to provide transcriptomic evidenee to further understand the fecundity of BPH.

Influence of Temperature on Symbiotic Bacterium Composition in Successive Generations of Egg Parasitoid, Anagrus nilaparvatae

Anagrus nilaparvatae is the dominant egg parasitoid of rice planthoppers and plays an important role in biological control. Symbiotic bacteria can significantly influence the development, survival, reproduction and population differentiation of their hosts. To study the influence of temperature on symbiotic bacterial composition in the successive generations of A. nilaparvatae, A. nilaparvatae were raised under different constant temperatures of 22 °C, 25 °C, 28 °C, 31 °C and 34 °C. Polymerase chain reaction-denaturing gradient gel electrophoresis was used to investigate the diversity of symbiotic bacteria. Our results revealed that the endophytic bacteria of A. nilaparvatae were Pantoea sp., Pseudomonas sp. and some uncultured bacteria. The bacterial community composition in A. nilaparvatae significantly varied among different temperatures and generations, which might be partially caused by temperature, feeding behavior and the physical changes of hosts. However, the analysis of wsp gene showed that the Wolbachia in A. nilaparvatae belonged to group A, sub-group Mors and sub-group Dro. Sub-group Mors was absolutely dominant, and this Wolbachia composition remained stable in different temperatures and generations, except for the 3rd generation under 34 °C during which sub-group Dro became the dominant Wolbachia. The above results suggest that the continuous high temperature of 34 °C can influence the Wolbachia community composition in A. nilaparvatae.

STATISTICAL ANALYSIS ON THE INFLUENCE OF THE LANDFALLING STRONG TROPICAL CYCLONES IN THE CATASTROPHIC MIGRATIONS OF NILAPARVATA LUGENS(STL) IN CHINA

In order to clarify the statistical pattern by which landfalling strong tropical cyclones(LSTCs)influenced the catastrophic migrations of rice brown planthopper(BPH),Nilaparvata lugens(stl)in China,the data of the LSTCs in China and the lighting catches of BPH that covered the main Chinese rice-growing regions from 1979 to 2008 were collected and analyzed in this work with the assistance of ArcGIS9.3,a software of geographic information system.The results were as follows:(1)In China,there were 220 strong tropical cyclones that passed the main rice-growing regions and 466 great events of BPH’s immigration in the 30 years from 1979 to 2008.73 of them resulted in the occurrence of BPH’s catastrphic migration(CM)events directly and 147 of them produced indirect effect on the migrations.(2)The number of the LSTCs was variable in different years during 1979 to 2008 and their influence was not the same in the BPH’s northward and southward migrations in the years.In the 30 years,the LSTCs brought more obvious influence on the migrations in 1980,1981,2005,2006 and 2007.The influence was the most obvious in2007 and all of the 7 LSTCs produced remarkable impact on the CMs of BPH’s populations.The effect of the LSTCs on the northward immigration of BPH’s populations was the most serious in 2006 and the influence on the southward immigration was the most remarkable in 2005.(3)In these years,the most of LSTCs occurred in July,August and September and great events of BPH's immigration occurred most frequently in the same months.The LSTCs played a more important role on the CM of BPH’s populations in the three months than in other months.(4)The analysis on the spatial distribution of the LSTCs and BPH’s immigration events for the different provinces showed that the BPH’s migrations in the main rice-growing regions of the Southeastern China were influenced by the LSTCs and the impact was different with the change of their spatial probability distribution during their passages.The most serious influence of the LSTCs on the BPH’s migrations occurred in Guangdong and Fujian provinces.(5)The statistical results indicated that a suitable insect source is an indispensable condition of the CMs of BPH when a LSTC influenced a rice-growing region.

Wing patterning genes of Nilaparvata lugens identification by transcriptome analysis, and their differential expression profile in wing pads between brachypterous and macropterous morphs

The brown planthopper, Nilaparvata lugens is an economically important pest on rice plants. This species produces macropterous and brachypterous morphs in response to environmental cues, which makes it very dififcult to control. The molecular basis of wing patterning in N. lugens is stil unknown. It is necessary to identify wing patterning genes of N. lugens, and also to clarify the expression differences of wing patterning genes between macropterous and brachypter-ous morphs. High-throughput deep sequencing of transcriptome of N. lugens wing pad yielded 116 744 580 raw reads and 113 042 700 clean reads. Al the reads were assembled into 55 963 unigenes with an average length of 804 bp. With the E-value cut-off of 1.0E–5,18 359 and 2 883 unigens had hits in NCBI-NR (NCBI non-redundant protein sequences) and NCBI-NT (NCBI nucleotide sequences) databases, respectively. A total of 16 502 unigenes were assigned to GO (gene ontology) classiifcation, 9 709 ungenes were grouped into 26 COG (cluster of orthologous groups of proteins) classiifcations, and 6 724 unigenes were assigned to different KEGG (Kyoto encyclopedia of genes and genomes) path-ways. In total, 56 unigenes which are homologous to wing patterning genes of Drosophila melanogaster or Tribolium castaneum were identiifed. Out of the 56 unigenes, 24 unigenes were selected, and their expression levels across the ifve nymphal stages between macropterous strain and brachypterous strain were examined by qRT-PCR. Two-way ANOVA analysis showed that development stage had signiifcant effects on the expression level of al the 24 genes (P<0.05). The expression levels of 8 genes (Nlen, Nlhh, Nlsal, NlAbd-A, Nlwg, Nlvg, Nlexd and NlUbx) were signiifcantly affected by wing morph. This is the ifrst transcriptome analysis of wing pads of hemimetabolous insect, N. lugens. The identiifed wing patterning genes would be useful resource for future exploration of molecular basis of wing development. The 8 differential y expressed wing patterning genes between macropterous strain and brachypterous strain would contribute to explain molecular mechanism of wing-morph differentiation in N. lugens.

INFLUENCE OF THE ASIAN SUMMER MONSOON ON THE MIGRATION PHENOLOGY AND POPULATION DYNAMICS OF NILAPARVATA LUGENS(ST?L) IN CHINA

With the aim to examine variations in the migration phenology and population of N. lugens along with the advance/retreat of the Asian summer monsoon(ASM) and lay the foundation for further study on predicting the timing and location of N. lugens outbreak, correlation analysis and spatial analysis were applied for estimating the impact of the ASM and its related meteorological factors on the migration phenology and population of N. lugens in China in this paper. The ASM had a positive effect on the occurrence and outbreak of N. lugens. First, the first appearance date of N.lugens was consistent with seasonal advances of the northernmost location of the ASM, and the ASM provided the dynamic condition for the northward migration of N. lugens. Second, outbreak of N. lugens occurred in the area under the control of the ASM, and the ASM provided the survival condition for the population of N. lugens. Third, the population was positively related to the northernmost location of the ASM, θ_E(850 hPa) and wind speed(850 hPa).Particularly, the stronger southwest wind caused the date of the first, peak and last catches of N. lugens to turn up earlier than in the extremely years.

Effects of a novel mesoionic insecticide,triflumezopyrim,on the feeding behavior of rice planthoppers,Nilaparvata lugens and Sogatella furcifera(Hemiptera:Delphacidae)

The rice planthoppers,Nilaparvata lugens and Sogatella furcifera,are important sap-sucking pests of rice in Asia.The mesoionic insecticide tifumezopyrim was previously shown to be highly effective in controlling both N.lugens and S.furcifera.In this study,electropenetrography(EPG)was used to evaluate the effect of three triflumezopyrim concentrations(LC。LC。and LC)on the feeding behavior of N.lugens and S.furcifera.EPG signals of planthoppes indicated that there were six different waveforms NP,N1,N2,N3,N4,and N5,which corresponded to non-penetration,stylet penetration into epidermis,salivation,extracellular movement of stylet,sap ingestion in phloem,and water ingestion in xylem during feeding.Compared to untreated controls,triflumezopyrim at LC。and LC。prolonged the duration of the non-penetration period by 105.3 to 333.7%.The probing frequencies of N.lugens exposed to tiflumezopyrim at LC1。and LCso were significantly increased;however,the probing frequencies of S.furcifera showed a significant decrease when exposed to triflumezopyrim at all concentrations.Triflumezopyrim exposure prolonged the duration of salivation and shortened the duration of extracellular movement.The duration of phloem sap ingestion decreased from 37.2 to 77.7%in the LCgo and LCgo treatments,respectively.Differences in feeding behavior in response to triflumezopyrim and pymetrozine were minimal.In summary,the results show that the LC。and LCgo concentrations of trflumezopyrim inhibit the feeding activities of N.lugens and S.furcifera mainly by prolonging the duration of non penetration and by shortening the duration of phloem sap ingestion,which may foster more efficient use of triflumezopyrim in Asia.

Amplification and function analysis of N6-adenine-specific DNA methyltransferase gene in Nilaparvata lugens

Methylation of the N6 position of adenine, termed N6-methyladenine, protects DNA from restriction endonucleases via the host-specific restriction-modification system. N6-methyladenine was discovered and has been well studied in bacteria. N6-adenine-specific DNA methyltransferase（N6AMT） is the main enzyme catalyzing the methylation of the adenine base and knowledge of this enzyme was mainly derived from work in prokaryotic models. However, large-scale gene discovery at the genome level in many model organisms indicated that the N6AMT gene also exists in eukaryotes, such as humans, mice, fruit flies and plants. Here, we cloned a N6AMT gene from Nilaparvata lugens（Nlu-N6AMT） and amplified its fulllength transcript. Then, we carried out a systematic investigation of N6AMT in 33 publically available insect genomes, indicating that all studied insects had N6AMT. Genomic structure analysis showed that insect N6AMT has short introns compared with the mammalian homologs. Domain and phylogenetic analysis indicated that insect N6AMT had a conserved N6-adenine Mlase domain that is specific to catalyze the adenine methylation. Nlu-N6AMT was highly expressed in the adult female. We knocked down Nlu-N6AMT by feeding ds RNA from the second instar nymph to adult female, inducing retard development of adult female. In all, we provide the first genome-wide analysis of N6AMT in insects and presented the experimental evidence that N6AMT might have important functions in reproductive development and ovary maturation.

Tolerance evaluation of rice varieties to the brown planthopper,Nilaparvata lugens feeding

The brown planthopper,Nilaparata lugens(Stl)(BPH)is one of the most important insect pests of rice in China and other east-southern Asian countries.Untilization of rice resistance varieties is one of the most econnomic and effective ways for

Susceptibility to Insecticides and Ecological Fitness in Resistant Rice Varieties of Field Nilaparvata lugens Stl Population Free from Insecticides in Laboratory

A population of rice brown planthopper （BPH） Nilaparvata lugens collected from a paddy field in Hangzhou was successively reared on susceptible rice Taichung Native 1 （TN1） in a laboratory free from insecticides for more than 14 generations. The changes in susceptibility to insecticides and ecological fitness on different resistant rice varieties were monitored in each generation. The resistance ratio to imidacloprid sharply declined with the succession of rearing generations without insecticides from 359.94-fold at F1 to 6.50-fold at F14 compared with the susceptible strain, and the resistance ratio to chlorpyrifos was from 9.90-fold at F1 to 5.94-fold at F14. Nymphal duration and weights of newly hatched female adults were significantly affected by rice variety, generation and their interactions, but nymphal survival was significantly affected by the generation only. The ratio of brachypterous adults in males was affected by the generation and generation × variety interaction, whereas no difference was found in females. Nymphal duration extended with increasing generations, and the female nymphal duration was shorter in the susceptible variety TN1 than those in the resistant varieties IR26 and IR36. In addition, the female adult weight in TN1 was higher than those in IR26 and IR36. These results indicated that the resistance of field BPH population to insecticides was reversed after several generations of no-exposure to insecticides, and the ecological fitness in TN1 was higher than those in IR26 and IR36. These findings suggested the rational and reduced use of insecticides in combination with the manipulation of resistant rice varieties would be effective for BPH management.

Relationship Between the Development of Methamidophos Resistance and the Activities of Three Detoxifying Enzymes in Brown Planthopper, Nilaparvata lugens

Methamidophos resistance of brown planthopper(BPH), Nilaparvata lugens was selected in laboratory for 19 generations (F1 to F19). The resistance development in BPH was approximatively shaped as the letter 'S' : resistance change was small before the fifth generation and after the fifteenth generation, and the changing pattern was sharp between the fifth and the fifteenth generation. Esterase might play an important role in the resistance development, because the esterase activity and the number of individuals with high activities increased along with the resistance development. The esterase activities of insecticide-sensitive population S, field population F0, its selective generations F5, F10 and F15 were highly correlated with the resistance ratios of these generations, and the coefficient was 0.9899. Mixed-function oxidases and glutathione S-transferase also might play some roles in the resistance development, but the big change in the activities of the two detoxifying enzymes both took place before the tenth generation.