Automated detection and identification of white-backed planthoppers in paddy fields using image processing

A survey of the population densities of rice planthoppers is important for forecasting decisions and efficient control. Traditional manual surveying of rice planthoppers is time-consuming, fatiguing, and subjective. A new three-layer detection method was proposed to detect and identify white-backed planthoppers(WBPHs, Sogatella furcifera(Horváth)) and their developmental stages using image processing. In the first two detection layers, we used an Ada Boost classifier that was trained on a histogram of oriented gradient(HOG) features and a support vector machine(SVM) classifier that was trained on Gabor and Local Binary Pattern(LBP) features to detect WBPHs and remove impurities. We achieved a detection rate of 85.6% and a false detection rate of 10.2%. In the third detection layer, a SVM classifier that was trained on the HOG features was used to identify the different developmental stages of the WBPHs, and we achieved an identification rate of 73.1%, a false identification rate of 23.3%, and a 5.6% false detection rate for the images without WBPHs. The proposed three-layer detection method is feasible and effective for the identification of different developmental stages of planthoppers on rice plants in paddy fields.

Efficient nanoparticle-based CRISPR-Cas13d induced mRNA disruption of an eye pigmentation gene in the white-backed planthopper,Sogatella furcifera

The discovery of the clustered regularly interspaced short palindromic repeat(CRISPR)system has driven gene manipulation technology to a new era with applications reported in organisms that span the tree of life.The utility of CRISPR-mediated editing was further expanded to mRNA following identification of the RNA-targeting Cas13 family of smaller endonuclease proteins.Application of this family to insect research,however,has been more limited.In this study,the smallest Cas13 family member,Cas13d,and guide RNAs(gRNAs)were complexed with a versatile nanomaterial(star polycation,SPc)to generate a proof-of-concept RNA-editing platform capable of disrupting mRNA expression of the eye pigmentation gene tryptophan 2,3-dioxygenase(SfTO)in white-backed planthoppers(WBPHs).The resulting red-eye phenotype was present in 19.76%(with SPc)and 22.99%(without SPc)of the treatment groups and was comparable to the red-eye phenotype generated following conventional RNA interference knockdown(22.22%).Furthermore,the Cas13/gRNA phenotype manifested more quickly than RNA interference.Consistent with the expected Cas13d mechanism,SfTO transcript levels were significantly reduced.Taken together,the results indicate that the SPc-CRISPR-Cas13d/gRNA complex negatively impacted expression of the target gene.These findings confirm the utility of this novel mRNA disruption system in insects and lay the foundation for further development of these tools in the implementation of green agricultural pest management tactics.

Induced defense responses in rice plants against small brown planthopper infestation

The small brown planthopper(SBPH), Laodelphax striatellus Fallén(Homoptera: Delphacidae), is a serious pest of rice(Oryza sativa L.) in China. To understand the mechanisms of rice resistance to SBPH, defense response genes and related defense enzymes were examined in resistant and susceptible rice varieties in response to SBPH infestation. The salicylic acid(SA) synthesis-related genes phenylalanine ammonia-lyase(PAL), NPR1, EDS1 and PAD4 were induced rapidly and to a much higher level in the resistant variety Kasalath than in the susceptible cultivar Wuyujing 3 in response to SBPH infestation. The expression level of PAL in the Kasalath rice at 12 h post-infestation(hpi) increased 7.52-fold compared with the un-infested control, and the expression level in Kasalath was 49.63, 87.18, 57.36 and 75.06 times greater than that in Wuyujing 3 at 24, 36, 48 and 72 hpi, respectively. However, the transcriptional levels of the jasmonic acid(JA) synthesis-related genes LOX and AOS2 in resistant Kasalath were significantly lower than in susceptible Wuyujing 3 at 24, 36, 48 and 72 hpi. The activities of the defense enzymes PAL, peroxidase(POD), and polyphenol oxidase(PPO) increased remarkably in Kasalath in response to SBPH infestation, and were closely correlated with the PAL gene transcript level. Our results indicated that the SA signaling pathway was activated in the resistant Kasalath rice variety in response to SBPH infestation and that the gene PAL played a considerable role in the resistance to SBPH.

Donors for Resistance to Brown Planthopper Nilaparvata lugens(St?l) from Wild Rice Species

Out of 1 989 wild accessions sown in seed boxes for screening, only 1 003 wild accessions with good germination were screened against brown planthopper(BPH), Nilaparvata lugens(St?l) under greenhouse conditions. The collection comprised of accessions from 11 wild species and African cultivated rice. The germplasm was screened for BPH following standard seed box screening technique in the greenhouse. As many as 159 accessions were identified as resistant during the year 2012 based on one year screening. A selected set of BPH resistant accessions were screened again during 2013. Based on the two years screening, seven accessions of O. nivara(AA), one accession of O. officinalis(CC), seven accessions of O. australiensis(EE), five accessions of O. punctata(BB and BBCC) and nine accessions of O. latifolia(CCDD) were confirmed to be resistant to BPH. So far no BPH resistance genes have been identified and designated from O. nivara and O. punctata, hence these may act as new sources of resistance.

LncRNAs are potentially involved in the immune interaction between small brown planthopper and rice stripe virus

Small brown planthopper(SBPH, Laodelphax striatellus Fallén) is an important vector of major crop pathogen rice stripe virus(RSV). Controlling SBPH population is an efficient approach to control RSV. Long non-coding RNAs(lnc RNA) have been reported to block virus replication in hosts. However, the function of lnc RNAs in RSV infection and replication is still unknown. Here, we aimed to study regulatory mechanisms of lnc RNA in an immune system during RSV infection. First, lnc RNA genes were predicted from SBPH transcriptomes using a bioinformatics pipeline based on characteristics of lnc RNA. We identified 4 786 lnc RNA genes corresponding to 5 790 transcripts in SBPH from an RNA-Seq dataset of 15 transcriptomes. Differential expression analysis indicated that 3, 11, and 25 lnc RNA genes were highly expressed in gut, salivary gland, and ovary, respectively, of viruliferous SBPH(Student’s t-test, P<0.05). We randomly selected eight lnc RNAs for expression validation using quantitative real-time PCR, confirming the differential expression of these lnc RNAs between viruliferous and non-viruliferous SBPH. In summary, we present evidence that the expression of lnc RNA genes was induced by RSV infection, suggesting that RSV might be involved in the antivirus immune system in SBPH and participate in regulating the RSV replication mechanism. These data provide helpful information for future investigations of the interaction between lncRNA and RSV.

Expression Analysis of Genes Related to Rice Resistance Against Brown Planthopper, Nilaparvata lugens

Brown planthopper(BPH) is an insect species that feeds on the vascular system of rice plants. To examine the defence mechanism of rice plants against BPH, the pathogenesis-related genes(PR1a, PR2, PR3, PR4, PR6, PR9, PR10a, PR13, PR15 and PRpha), signaling molecule synthesis genes(AOS, AXR, ACO and LOX), antioxidant-related genes(CAT, TRX, GST and SOD) and lignin biosynthesis-related genes(CHS, CHI and C4H) were investigated in a resistant rice variety. AOS, PR6,PR9 and PR15 genes showed significantly increased relative expression levels at 24.38-, 19.17-, 14.71-, and 12.74-fold compared to the control. Moderate increased relative expression levels of lignin biosynthesis-related gene(C4H), pathogenesis-related genes(PR4, PR10a and PRpha), and antioxidant-related gene(GST) were found, while CHI, LOX, SOD, TRX1 and AXR showed decreased relative expression levels. It was thus clearly shown that wound-induced response genes were activated in rice plants after BPH attacks through AOS activation. Jasmonic acid signaling molecule may activate PR6, PR15, GST and CAT subsequently increasing their expression for H_2O_2 detoxification. PR6 were expressed at the highest relative level among the PR genes. These genes therefore have also a considerable synergistic role with the other genes against BPH by interfered their digestion tract system.

Effects of Temperature on Functional Response of Anagrus nilaparvatae Pang et Wang (Hymenoptera:Mymaridae) on the Eggs of Whitebacked Planthopper,Sogatella furcifera Horvth and Brown Planthopper,Nilaparvata lugens Stl

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 Stl 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.

Identification of a novel planthopper resistance gene from wild rice(Oryza rufipogon Griff.)

Rice planthoppers,including brown planthopper(BPH)and white-backed planthopper(WBPH),are the most destructive pests in Asian rice cultivation regions.Planthopper resistance genes that have been mapped and characterized advance our understanding of underlying resistance mechanisms and facilitate the breeding of resistant varieties,thereby contributing to an efficient pest management strategy.In this study,a novel resistance gene Bph38 derived from the wild rice species Oryza rufipogon Griff.was found to confer high resistance to BPH and WBPH.Conventional mapping was performed to identify regions associated with BPH and WBPH resistance,and two mapping efforts led to the same region on chromosome 4 flanked by markers RM16563 and RM16763.Bulked-segregant analysis and next-generation sequencing were performed using the same population to detect the resistance gene.Conventional mapping narrowed the region to a 12.3-Mb segment,and fine mapping using BC1 F2 recombinants identified a 79-kb segment flanked by markers YM112 and YM190.Near-isogenic lines(NILs)carrying Bph38 in the 9311(indica)and BR54(japonica)genetic backgrounds were developed by crossing and backcrossing with marker-assisted selection.The agronomic traits and BPH and WBPH resistance of the NILs were similar to those of the recurrent parents.Mandatory feeding and host-choice tests revealed that Bph38 showed both antibiotic and antixenotic effects in both insects,with stronger effects in indica-background lines.Further fine mapping and characterization of the major gene may result in map-based cloning of the gene and allow its application in breeding insectresistant rice varieties.

Identification of Major Locus Bph35 Resistance to Brown Planthopper in Rice

An introgression line RBPH660,derived from wild rice Oryza rufipogon,showed stable resistance to brown planthopper(BPH).Segregation analysis indicated BPH resistance of RBPH660 was controlled by multiple genes/QTLs.By using the bulked segregant analysis(BSA)-seq method,two genomic regions harboring QTLs resistance to BPH were identified from 1.20 to 16.70 Mb on chromosome 4 and from 10.20 to 12.60 Mb on chromosome 9 in RBPH660,respectively.A major resistance locus,designated as Bph35 accounting for 51.27%of the phenotypic variation with a LOD score of 42.51,was mapped to the candidate region of chromosome 4 between In Del(insertion-deletion)markers PSM16 and R4 M13.For fine mapping of Bph35,one simple sequence repeat and three newly developed In Del markers were used to screen the recombinants.Finally,the Bph35 locus was delimited in the region from 6.28 to 6.93 Mb and there were 18 predicted protein-encoding genes with a total of 114 non-synonymous single nucleotide polymorphism(SNP)variant sites between the resistant and susceptible parents.Out of these genes,Os04 g0193950,encoding a putative NB-ARC(nucleotidebinding adaptor shared by APAF-1,R proteins and CED-4)and LRR(leucine-rich repeat)domain protein with nine non-synonymous SNP substitutions in its coding sequence regions,might be the candidate gene for Bph35.These findings would facilitate the map-based cloning of the Bph35 gene and development of resistant varieties against BPH in rice.

Improving the resistance of the rice PTGMS line Feng39S by pyramiding blast,bacterial blight,and brown planthopper resistance genes

Knowledge of rice(Oryza sativa L.)genes and various DNA markers can be used in genomic breeding programs aimed at developing improved elite rice cultivars.We used an efficient genomic breeding approach to pyramid four resistance genes(Pi2,Xa23,Bph14,and Bph15)in the popular photoperiod-and thermosensitive genic male sterile(PTGMS)rice line Feng39S.We performed foreground selection for the target genes,followed by recombinant selection and background selection.This process reduced the sizes of the genomic segments harboring the target genes(566.8 kb for Pi2,1143.9 kb for Xa23,774.7 kb for Bph14,and 1574.9 kb for Bph15)and accelerated the recovery of the recurrent parent genome to proportions ranging from 98.77%to 99.16%,thus resulting in four near-isogenic lines.To assemble the four resistance genes in Feng39S,we performed a double-way cross combined with foreground and background selection to generate two improved lines of Feng39S(Pi2+Xa23+Bph14+Bph15)with a recurrent parent genome recovery of 98.98%.The two lines showed agronomic performance,grain quality,and fertility–sterility transition characteristics similar to those of the original Feng39S line.The newly developed PTGMS lines and corresponding hybrid combinations were resistant to various field blast isolates and seven representative isolates of bacterial blight.At the seedling stage,the lines also showed resistance against brown planthopper.This study provides an efficient and accurate genomic breeding approach for introducing desirable traits into PTGMS lines.

Understanding Brown Planthopper Resistance in Rice: Genetics, Biochemical and Molecular Breeding Approaches

Brown planthopper(BPH,Nilaparvata lugens St自I)is the most devastating pest of rice in Asia and causes significant yield loss annually.Around 37 BPH resistance genes have been identified so far in indica,African rice varieties along with wild germplasms such as Oryza officinalis,O.minuta,O.nivara,O.punctata,O.rufipogon and O,latifolia.Genes/QTLs involved in BPH resistance,including Bph1,bph2/BPH26,Bph3,Bph6,bph7,BPH9,Bph12,Bph14,Bph15,Bph17,BPH18,bph19,Bph20,Bph21(t),Bph27,Bph27©Bph28(t),BPH29,QBph3,QBph4,QBph4.2,Bph30,Bph32,Bph33,Bph35 and Bph36,have been fine-mapped by different researchers across the globe.The majority of genes/QTLs are located on rice chromosomes 1,3,4,6,11 and 12.Rice plants respond to BPH attack by releasing various endogenous metabolites like proteinase inhibitors,callose,secondary metabolites(terpenes,alkaloids,flavonoid,etc.)and volatile compounds.Besides that,hormonal signal pathways mediating(antagonistic/synergistic)resista nee responses in rice have been well studied.Marker-assisted breedi ng and genome editi ng techniq ues can also be adopted for improving resista nee to novel BPH biotypes.

Pyramiding blast,bacterial blight and brown planthopper resistance genes in rice restorer lines

Rice blast, bacterial blight(BB) and brown planthopper(BPH) are the three main pests of rice. This study investigated pyramiding genes resistant to blast, BB and BPH to develop restorer lines. Ten new lines with blast, BB and/or BPH resistance genes were developed using marker-assisted selection(MAS) technique and agronomic trait selection(ATS) method. Only HR13 with resistance genes to blast, BB and BPH was obtained. In addition to blast and BB resistance, four lines(HR39, HR41, HR42, HR43) demonstrated moderate resistance to BPH, but MAS for BPH resistance genes were not conducted in developing these four lines. These data suggested that there were unknown elite BPH resistance genes in the Zhongzu 14 donor parent. A more effective defense was demonstrated in the lines with Pi1 and Pi2 genes although the weather in 2012 was favorable to disease incidence. Blast resistance of the lines with a single resistance gene, Pita, was easily influenced by the weather. Overall, the information obtained through pyramiding multiple resistance genes on developing the restorer lines is helpful for rice resistance breeding.

The Influence of Transgenic cry1Ab/cry1Ac,cry1C and cry2A Rice on Non-Target Planthoppers and Their Main Predators Under Field Conditions

Transgenic Bt rice has been shown to be an effective means of controlling Lepidoptera pests of rice.However,the potential roles of transgenic rice on planthoppers and their predators need to be investigated before its commercialization.Population density,species dominance and population dynamics are important parameters of arthropods populations in field.So the impacts of three transgenic Bt rice strains expressing cry1Ab/cry1Ac,cry1C and cry2A on population density,species dominance and population dynamics of three species of planthoppers(Nilaparvata lugens,Sogatella furcifera and Laodelphax striatellus) and their three main predators(Cyrtorhinus lividipennis,Pirata subpiraticus and Theridium octomaculatum) were evaluated at three sites in Hubei Province,China,in the current study.The results showed that among three species of planthoppers,both in transgenic and non-transgenic rice field,the predominant species of planthoppers within phytophagous guild was S.furcifera at any site either growing season(46-50%).Significantly higher population density of N.lugens was observed in T2A-1 field relative to Minghui 63 field at Wuxue in 2010.The species dominance of predator,P.subpiraticus,in TT51 field was significantly higher than that in T1C-19 and T2A-1 fields in 2009 at Xiaogan site.Sampling date significantly influenced six arthropods except for P.subpiraticus in 2010.The interaction between rice strain×sampling date had no significant adverse effects on the population dynamics of three species of planthoppers and their predators,except for several individual species in 2009.The interaction among rice strain×sampling date×sampling site also had no significant effect on six arthropods except for S.furcifera in 2009.The results indicated that transgenic Bt rice expressing cry1Ab/cry1Ac,cry2A and cry1C had no significant adverse effects on the population dynamics of three planthoppers and their predators in most investigated data and sampling site.

Automated Counting of Rice Planthoppers in Paddy Fields Based on Image Processing

A quantitative survey of rice planthoppers in paddy fields is important to assess the population density and make forecasting decisions. Manual rice planthopper survey methods in paddy fields are time-consuming, fatiguing and tedious. This paper describes a handheld device for easily capturing planthopper images on rice stems and an automatic method for counting rice planthoppers based on image processing. The handheld device consists of a digital camera with WiFi, a smartphone and an extrendable pole. The surveyor can use the smartphone to control the camera, which is fixed on the front of the pole by WiFi, and to photograph planthoppers on rice stems. For the counting of planthoppers on rice stems, we adopt three layers of detection that involve the following:(a) the first layer of detection is an AdaBoost classifier based on Haar features;(b) the second layer of detection is a support vector machine(SVM) classifier based on histogram of oriented gradient(HOG) features;(c) the third layer of detection is the threshold judgment of the three features. We use this method to detect and count whiteback planthoppers(Sogatella furcifera) on rice plant images and achieve an 85.2% detection rate and a 9.6% false detection rate. The method is easy, rapid and accurate for the assessment of the population density of rice planthoppers in paddy fields.

Effect of Nitrogen on Water Content, Sap Flow, and Tolerance of Rice Plants to Brown Planthopper, Nilaparvata lugens

Water content (WC) and sap flow from leaf sheath of rice plants with varying nitrogen levels at different growth stages and fluctuations in relative water content (RWC) of rice plants being damaged by brown planthopper (BPH), Nilaparvata lugens were determincd in the laboratory, and the tolerance of rice plants to BPH at different nitrogen regimes was evaluated in the greenhouse at International Rice Research institute (1RRI), the Philippines. The results indicated that both WC and RWC were increased significantly, as the amount of sap flow from rice plants was reduced statistically, with the in crease of nitrogen content inrice plants. RWC in rice plants applied with high nitrogen fertilizer decreased drastically by the injury, of BPH nymphs, while the reduced survival duration of rice plants with the increase of nitrogen content was recorded. These may be considered to be one of the important factors in increasing the susceptibility' to BPH damage on rice plants applied with nitrogen

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

To investigate the effect of temperature on the resistance characteristics of rice varieties with different resistance genes to brown planthopper(BPH),Nilaparvata lugens(Stl),the resistances of IR26(Bph1)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.

Content Variations of the Secondary Compounds in Rice Plants and Their Influence on Rice Resistance to Brown Planthopper,Nilaparvata lugens

Content variations of the four components in the plants of rice ASD7, IR36 (resistant to brown planthopper) and TN1 (susceptible to brown planthopper), and their influence on rice resistance to brown planthopper (BPH, Nilaparvata lugens) were investigated. The resistance diversity of rice to BPH biotype II at different plant ages was chiefly attributed to the content variability of the secondary compounds. The contents in the leaf sheath were the lowest as compared with other parts of rice plant. It might explain the reason that BPH has a preference for feeding on leaf sheath aggregately from chemical point of view.

Ecological Fitness of Non-vector Planthopper Sogatella furcifera on Rice Plants Infected with Rice Black Streaked Dwarf Virus

We evaluated the effects of rice black streak dwarf virus(RBSDV)-infested rice plants on the ecological parameters and its relevant defensive and detoxification enzymes of white-backed planthopper(WBPH) in laboratory for exploring the relationship between RBSDV and the non-vector planthopper.The results showed that nymph survival rate,female adult weight and fecundity,and egg hatchability of WBPH fed on RBSDV-infested rice plants did not markedly differ from those on healthy plants,whereas the female adult longevity and egg duration significantly shortened on diseased plants.Furthermore,significantly higher activities of defensive enzymes(dismutase,catalase and peroxidase) and detoxification enzymes(acetylcholinesterase,carboxylesterase and glutathione S-transferase) were found in WBPH adults fed on infected plants.Results implied that infestation by RBSDV increased the ecological fitness of non-vector planthopper population.

Evaluation of Rice Germplasm for Resistance to the Small Brown Planthopper (Laodelphax striatellus) and Analysis of Resistance Mechanism

One hundred and thirty-eight rice accessions were screened for resistance to the small brown planthopper (SBPH) (Laodelphax striatellus Fallén) by the modified seedbox screening test. Twenty-five rice accessions with different levels of resistance to SBPH were detected, accounting for 18.1% of the total accessions, which included 2 highly resistant, 9 resistant and 14 moderately resistant varieties. Compared with indica rice, japonica rice was more susceptible to SBPH. Antixenosis test, antibiosis test and correlation analysis were performed to elucidate the resistance mechanism. The resistant check Rathu Heenati (RHT), highly resistant varieties Mudgo and Kasalath, and resistant variety IR36 expressed strong antixenosis and antibiosis against SBPH, indicating the close relationship between resistance level and these two resistance mechanisms in the four rice varieties. Antibiosis was the dominant resistance pattern in the resistant varieties Daorenqiao and Yangmaogu due to their high antibiosis but low antixenosis. Dular, ASD7 and Milyang 23 had relatively strong antixenosis and antibiosis, indicating the two resistance mechanisms were significant in these three varieties. The resistant DV85 expressed relatively high level of antixenosis but low antibiosis, whereas Zhaiyeqing 8 and Guiyigu conferred only moderate antibiosis and antixenosis to SBPH, suggesting tolerance in these three varieties. Antibiosis and antixenosis governed the resistance to SBPH in the moderately resistant accession 9311. Antixenosis was the main resistance type in V20A. Tolerance was considered to be an important resistance mechanism in Minghui 63 and Yangjing 9538 due to their poor antibiosis and antixenosis resistance. The above accessions with strong antibiosis or antixenosis were the ideal materials for the resistance breeding.

Molecular Characterization and Functional Analysis of Krüppel-homolog 1(Kr-h1) in the Brown Planthopper, Nilaparvata lugens(Stl)

The brown planthopper, Nilaparvata lugens(Stl), is the most serious insect pest of rice. It has developed high resistance to traditional insecticides because of their intensive use. Juvenile hormone(JH) analogs have been used successfully to control this species and other pest insects. However, the molecular mechanism of JH signaling is not well understood. Krüppel-homolog 1(Kr-h1) is a transcription factor involved in the JH pathway. In this study, the Kr-h1 cDNA was cloned and characterized from N. lugens by rapid amplification of cDNA ends(RACE) and reverse transcription PCR(RT-PCR). Its spatial and temporal expression profiles were examined by real-time quantitative PCR, and its function was also studied by RNA interference(RNAi). The open reading frame of NlKr-h1 is 1 833 bp encoding for 611 amino acids. The protein contains eight conserved zinc-finger motifs. NlKr-h1 was expressed at all life stages, with the highest mRNA level in the 4-day embryo. NlKr-h1 mRNA levels rose during each nymphal molt after the 2nd instar. In the adults, the mRNA level in males was significantly higher than that in females of either the macropterous or brachypterous type. The highest expression was observed in the female midgut. NlKr-h1 was activated by juvenile hormone III(JH III) in the 3rd-5th instar nymphs. Disruption of Nlkr-h1 expression by RNAi caused stunted wing development and malformations of both male and female external genitalia. Our findings suggest that Kr-h1 may be a useful target for pest insect management.