Insect Pest Of Rice Research Articles

Cycle affects imidacloprid efficiency by mediating cytochrome P450 expression in the brown planthopper Nilaparvata lugens.

Circadian clocks influence most behaviours and physiological activities in animals, including daily fluctuations in metabolism. However, how the clock gene cycle influences insects' responses to pesticides has rarely been reported. Here, we provide evidence that cycle affects imidacloprid efficacy by mediating the expression of cytochrome P450 genes in the brown planthopper (BPH) Nilaparvata lugens, a serious insect pest of rice. Survival bioassays showed that the susceptibility of BPH adults to imidacloprid differed significantly between the two time points tested [Zeitgeber Time 8 (ZT8) and ZT4]. After cloning the cycle gene in the BPH (Nlcycle), we found that Nlcycle was expressed at higher levels in the fat body and midgut, and its expression was rhythmic with two peaks. Knockdown of Nlcycle affected the expression levels and rhythms of cytochrome P450 genes as well as susceptibility to imidacloprid. The survival rates of BPH adults after treatment with imidacloprid did not significantly differ between ZT4 and ZT8 after double-stranded Nlcycle treatment. These findings can be used to improve pesticide use and increase pesticide efficiency in the field.

Transgenic Bt rice lines producing Cry1Ac, Cry2Aa or Cry1Ca have no detrimental effects on Brown Planthopper and Pond Wolf Spider

Transgenic rice expressing cry genes from the bacterium Bacillus thuringiensis (Bt rice) is highly resistant to lepidopteran pests. The brown planthopper (BPH, Nilaparvata lugens) is the main non-target sap-sucking insect pest of Bt transgenic rice. The pond wolf spider (PWS, Pardosa pseudoannulata) is one of the most dominant predators of BPH in rice fields. Consequently, the safety evaluation of Bt rice on BPH and PWS should be conducted before commercialization. In the current study, two experiments were performed to assess the potential ecological effects of Bt rice on BPH and PWS: (1) a tritrophic experiment to evaluate the transmission of Cry1Ac, Cry2Aa and Cry1Ca protein in the food chain; and (2) binding assays of Cry1Ac, Cry2Aa and Cry1Ca to midgut brush border membrane proteins from BPH and PWS. Trace amounts of the three Cry proteins were detected in BPH feeding on Bt rice cultivars, but only Cry1Ac and Cry2Aa proteins could be transferred to PWS through feeding on BPH. In vitro binding of biotinylated Cry proteins and competition assays in midgut protein vesicles showed weak binding, and ligand blot analysis confirmed the binding specificity. Thus, we inferred that the tested Bt rice varieties have negligible effects on BPH and PWS.

Ecological fitness of brown planthopper, Nilaparvata lugens (St\xe5l), to rice nutrient management

IntroductionThe brown planthopper (BPH), Nilaparvata lugens (Stål) (Hemiptera: Delphacidae), is a notorious insect pest of rice. Nutrient supplementation can alter plant biochemical compositions which may indirectly affect on ecological fitness parameters of its insect pest. However, few findings are available on nutrient-induced ecological fitness of BPH and relationship of BPH fitness parameters with its host rice plant biochemical contents.MethodsWe studied the main and interaction effects of nitrogen (N), phosphorus (P), and potassium (K) inputs on BPH fitness, as measured by the following variables: nymph survival, nymphal duration, adult body weight, and its survival. Brown planthopper fitness parameters were regressed as function of rice plant (Oryza sativa) biochemical composition. A completely randomized design with four replications in a factorial scheme was used considering N, P, and K levels as factors.ResultsNitrogen application to the host rice plants provided greater survival and enhanced body weight of BPH. The nymphal duration was found to decrease with N subsidy that caused shorter generation time of BPH. Nitrogenous compounds N and soluble protein (SP), total free sugar (TFS), and silicon (Si) content in rice plant tissue correlated strongly with all fitness traits of BPH. Nitrogen, SP, and TFS associated positively with BPH survival and body weight, while negatively with nymphal duration. In contrast, Si had negative correlation with BPH survival and body weight, but positive with nymphal duration. Phosphorus supplementation to host plant contributed to increase BPH body weight. Relationships of P with all parameters of BPH were weak except body weight which was highly significant and positive. Interaction between N and P inputs demonstrated significant effect on BPH body weight. Application of K had no significant effect on BPH survival and development. Regression analysis did not detect significant relationship of BPH fitness parameters with plant tissue content of K.ConclusionsThe results suggest that BPH ecological fitness characters were improved after N and P fertilization to rice plants which are associated with biochemical content of rice plant. Therefore, N and P inputs should be used judiciously in rice cultivation to keep BPH ecological fitness potential at minimum level.

De novo transcriptomic analysis to reveal insecticide action and detoxification-related genes of the predatory bug, Cyrtorhinus lividipennis

The mirid bug, Cyrtorhinus lividipennis Reuter, an important predatory natural enemy of rice planthoppers, is widely distributed in rice fields. However, genetic information on C. lividipennis is lacking. Especially, limited data about mechanisms of insecticide selectivity between this piercing-sucking predator (C. lividipennis) and piercing-sucking preys (rice planthoppers), inhibits development of selective insecticides and the integration of chemical and biological control systems to control insect pests of rice. Hence, we performed de novo assembly of a transcriptome from adult and nymph whole bodies of C. lividipennis. A total of >29 million of reads were generated, and 34,752 transcripts matched known proteins. Then, the genes related to insecticide action and detoxification were manually identified, including 26 carboxylesterases (containing 2 acetylcholinesterases), 57 cytochrome P450s, 19 glutathione S-transferases, 15 nicotinic acetylcholine receptors, 3 GABA-gated ion channels, and 1 glutamate receptor. Comparisons of sequence differences in these genes between C. lividipennis and rice planthoppers, revealed that quite a lot of diversity was found among genes related to insecticide action and detoxification, while a few of these genes share much higher identities between this predator and prey. The present study provides useful information for our understanding of insecticide selectivity between rice planthoppers and the predator mirid bug.

Silicon amendment to rice plants impairs sucking behaviors and population growth in the phloem feeder Nilaparvata lugens (Hemiptera: Delphacidae)

The brown planthopper (BPH), Nilaparvata lugens (Stål), is a migratory and destructive sucking insect pest of rice. Silicon (Si) amendment to plants can confer enhanced resistance to herbivores and is emerging as a novel approach for pest management. In the present study, we tested the effects of Si addition at 0.16 (low) and 0.32 (high) g Si/kg soil on sucking behaviors and population growth in BPH. Si amendment increased Si content in rice stems and extended non-probing event and phloem puncture followed by sustained phloem ingestion over that in the no-Si-addition control. High Si addition rate prolonged the stylet pathway and the time needed to reach the first phloem puncture, shortened durations of phloem puncture and phloem ingestion, and decreased the proportion of individuals that produced sustained phloem ingestion. BPH female feeding on and preference for plants with the high Si addition rate were also reduced. As a result, Si application significantly decreased BPH population growth rates while increased population doubling time. These results indicate that Si amendment, especially at the high rate, confers enhanced rice plant resistance to BPH through impairment of BPH feeding. Our results highlight the potential of Si amendment as an alternative for BPH management.

RNA interference knockdown of aminopeptidase N genes decrease the susceptibility of Chilo suppressalis larvae to Cry1Ab/Cry1Ac and Cry1Ca-expressing transgenic rice

Transgenic rice expressing Bacillus thuringiensis (Bt) Cry toxins are resistant to lepidopteran pests, such as Chilo suppressalis, a major insect pest of rice in Asia. Understanding how these toxins interact with their hosts is crucial to understanding their insecticidal action. In this study, knockdown of two aminopeptidase N genes (APN1 and APN2) by RNA interference resulted in decreased susceptibility of C. suppressalis larvae to the Bt rice varieties TT51 (Cry1Ab and Cry1Ac fusion genes) and T1C-19 (Cry1Ca), but not T2A-1 (Cry2Aa). This suggests that APN1 and APN2 are receptors for Cry1A and Cry1C toxins in C. suppressalis.

GEODATA: Information System Based on Geospatial for Early Warning Tracking and Analysis Agricultural Plant Diseases in Central Java

The Government of Indonesia is currently faced with the problems of food, especially rice. It needs in large numbers that have to import from neighboring countries. Actually, the Indonesian government has the ability to produce rice to meet national needs but is still faced with the problem of pest attack rice annually increasing extent. One of the factors is that geographically Indonesia located on the migration path of world rice insect pests (called BPH or Brown Planthoppers) (Nilaparvata lugens Stal.) It leads endemic status annually. One proposed strategy to be applied is to use an early warning system based on a specific region of the main pest population. The proposed information system called GEODATA. GEODATA is Geospatial Outbreak of Disease Tracking and Analysis. The system works using a library ESSA (Exponential Smoothing - Spatial Autocorrelation) developed in previous studies in Satya Wacana Christian University. GEODATA built to meet the qualifications required surveillance device by BMKG (Indonesian Agency of Meteorology, Climatology and Geophysics’ Central Java Provinces), BPTPH (Indonesian Agency of Plant Protection and Horticulture) Central Java Provinces, BKP-KP District Boyolali, Central Java, (Indonesian Agency of Food Security and Agriculture Field Supervisor, District Boyolali, Central Java Provinces) and farmer groups. GIS GEODATA meets the needs of surveillance devices that include: (1) mapping of the disease, (2) analysis of the dynamics of the disease, and (3) prediction of attacks / disease outbreaks in a particular region. GIS GEODATA is currently under implementation in the laboratory field observations of plant pest in Central Java province, Indonesia.

Gene expression and plant hormone levels in two contrasting rice genotypes responding to brown planthopper infestation

BackgroundThe brown planthopper (BPH; Nilaparvata lugens Stål) is a destructive piercing-sucking insect pest of rice. The plant hormones salicylic acid (SA) and jasmonic acid (JA) play important roles in plant–pest interactions. Many isolated rice genes that modulate BPH resistance are involved in the metabolism or signaling pathways of SA, JA and ethylene. ‘Rathu Heenati’ (RH) is a rice cultivar with a high-level, broad-spectrum resistance to all BPH biotypes. Here, RH was used as the research material, while a BPH-susceptible rice cultivar ‘Taichung Native 1’ (TN1) was the control. A cDNA microarray analysis illuminated the resistance response at the genome level of RH under BPH infestation. The levels of SA and JA in RH and TN1 seedlings after BPH infestation were also determined.ResultsThe expression pattern clustering indicated that 1467 differential probe sets may be associated with constitutive resistance and 67 with the BPH infestation-responsive resistance of RH. A Venn diagram analysis revealed 192 RH-specific and BPH-inducible probe sets. Finally, 23 BPH resistance-related gene candidates were selected based on the expression pattern clustering and Venn diagram analysis. In RH, the SA content significantly increased and the JA content significantly decreased after BPH infestation, with the former occurring prior to the latter. In RH, the differential genes in the SA pathway were synthesis-related and were up-regulated after BPH infestation. The differential genes in the JA pathway were also up-regulated. They were jasmonate ZIM-domain transcription factors, which are important negative regulators of the JA pathway. Comparatively, genes involved in the ET pathway were less affected by a BPH infestation in RH. DNA sequence analysis revealed that most BPH infestation-inducible genes may be regulated by the genetic background in a trans-acting manner, instead of by their promoters.ConclusionsWe profiled the analysis of the global gene expression in RH and TN1 under BPH infestation, together with changes in the SA and JA levels. SA plays a leading role in the resistance response of rice to BPH. Our results will aid in understanding the molecular basis of RH’s BPH resistance and facilitate the identification of new resistance-related genes for breeding BPH-resistant rice varieties.

The tiered-evaluation of the effects of transgenic cry1c rice on Cyrtorhinus lividipennis, a main predator of Nilaparvata lugens

T1C-19, a newly developed transgenic cry1C rice line, expresses cry1C under the control of the maize ubiquitin promoter, and is highly resistant to lepidopteran pests of rice. Cyrtorhinus lividipennis is the major predator of the eggs and young nymphs of Nilaparvata lugens, which is the main non-target sap-sucking insect pest of Bt rice. C. lividipennis may be exposed to Cry1C protein, thus biosafety evaluations of transgenic cry1C rice on C. lividipennis should be conducted before the commercialization of T1C-19. In the current study, we tested the direct toxicity of elevated doses of Cry1C to C. lividipennis, effects of T1C-19 on the life-table parameters of C. lividipennis via preying planthoppers, and effects of T1C-19 on the population density and dynamics in rice fields. No detrimental effects on development, survival, female ratio and body weight of C. lividipennis were caused by direct exposure to elevated doses of the Cry1C protein or prey-mediated exposure to realistic doses of the protein. The population density and dynamics did not significantly differ between C. lividipennis in T1C-19 and non-transgenic rice fields. Thus, transgenic cry1C rice had no negative effects on C. lividipennis. This is the first report of the effects of transgenic cry1C rice on C. lividipennis.

Knockdown of an ABC transporter leads to bright red eyes in the brown planthopper, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae)

Compound eye color is an important biological character of insects, which is determined by the nature of eye pigments. Ommochrome is the solely source of eye color for some insects, while pteridines is also needed for the other insect species. However, little is known about the eye pigment composition for any planthopper. Scarlet is an ABC (ATP-binding cassette) transporter protein, which functions as the transmembrane transporter for ommochrome precursor. The failure of Scarlet function can cause bright red or white eyes in different species, which depending on the nature of eye pigments. Here, we identified a scarlet ortholog gene (Nlst) from the brown planthopper (BPH), Nilaparvata lugens, which is a destructive insect pest of rice. Nlst is the first characterized eye pigment transporter gene from Hemipteran. NlSt, the protein deduced from Nlst, has an open reading frame (ORF) of 629 amino acids with the two sequence logos for eye pigment transporters. Expression profile revealed that Nlst expressed at all development stages and had the highest transcript level in head. Knockdown the Nlst transcript, the wild-type eye color partially changed to bright red, while not to white. Meantime, the ommochrome level in heads reduced to 73.4%. These results suggested that the eye coloration of BPH needs both ommochrome and pteridines pigments. Because nymphal RNAi with Nlst leading to a clearly distinguished phenotype from the control individuals, Nlst maybe a suitable genetic marker to exploit embryonic RNAi technique in this insect pest.

Structural characterization and applications of ITS2 from rice leaffolders Cnaphalocrocis medinalis and Marasmia patnalis (Lepidoptera: Pyralidae)

Cnaphalocrocis medinalis and Marasmia patnalis are important rice insect pests in Asia and have similar morphologic features and same feeding patterns. Understanding the molecular difference of the two leaffolders is helpful to their identification and clarification of their phylogenetic class in the Pyraloidea. In this study, we determined and analyzed the nucleotide sequences of nuclear rDNA internal transcribed spacer 2 (ITS2) in the two rice leaffolders from 9 populations (six C. medinalis populations collected from China, Philippine, Thailand, and Vietnam, and three M. patnalis populations from Philippine, Thailand, and Vietnam) and compared interspecies variation of IST2 among different geographic populations and intraspecies variation of ITS2 from Pyraloidea. Phylogenetic trees were constructed on the two leaffolders and other Pyraloidea species using Maximum Parsimony method. Results showed that the ITS2 sequences differed in the two leaffolders. Compared to C. medinalis, ITS2 of M. patnalis had small deletion at the sites of 41, 72, 81, 304 and an insertion at the site of 337. Interspecies variation results showed that three C. medinalis populations from Southeast Asia (VN, PH, and TH) are with small divergence compared to NJ and HZ, and small divergence was observed among three M. patnalis populations (VN, PH, and TH). Intraspecies variation results showed that two leaffolders were with close relationship compared to the other Pyraloidea. Phylogenetic trees showed that two leaffolders were grouped together with Maruca vitrata. These results indicated that the ITS2 sequences differed in the two leaffolders could potentially be used in the distinguishing of the two rice leaffolders and the determination on the phylogeny of species.

Head Shape Variation in Cnaphalocrocismedinalis (Guenee) Larvae Associated with Different Rice Varieties

Cnaphalocrosismedinalis is considered a dominant insect pest of rice throughout the rice growing areas in the Philippines. Its head, a morphological trait, is specialized for food gathering and manipulation, including its relation to bite performance and ecology has been used for investigating the integration of different phenotypic components. Because of the role of this structure in the insect pest, we quantitatively describe the amount of morphometric variation between populations of the pest collected from different rice hosts. Landmark-based geometric morphometrics method was used to quantify and analyze head shape variation by the application of statistical methods of the relative warp scores. Based on the results of the assessment, significant variations in head shapes between populations of the insect were observed and argued to be due to the selection exerted by the host.

Characterization of Resistance to the Green Rice Leafhopper (<i>Nephotettix cincticeps</i> Uhler) in a Core Collection of Landraces in Rice (<i>Oryza sativa</i> L.)

The green rice leafhopper (GRH; Nephotettix cincticeps Uhler) is one of the most devastating insect pests of cultivated rice (Oryza sativa L.) in temperate regions in Asia. Using the rice germplasms with biotic stress resistance is the most effective and environmentally-friendly way to control the insect pests in the paddy. Sixty accessions from a core set of worldwide collection of rice were characterized for resistance to the GRH by antibiosis test both at the seedling and at the booting stages. The positive correlations of average nymph mortality (ANM) were observed between at the seedling stage and at the booting stage on 3 days after infestation (DAI) (r = 0.684**), 5DAI (r = 0.680**), and 7DAI (r = 0.652**), respectively. This result will give us the opportunity to screen resistance to the GRH with the cost-efficient way using rice seedlings in a growth chamber. To classify the 60 accessions evaluated, the ANM of the GRH of each accession was compared to the respective ANM of resistant and susceptible controls with the least significant difference (LSD) value. Based on the statistical difference or similarity of the ANMs to the resistant and the susceptible controls, we proposed the four groups of resistance to the GRH, (I) high level of resistance, (II) considerable level of resistance, (III) moderate level of resistance, and (IV) susceptibility. At the seedling stage, a total of 26 accessions were highly resistant in addition to other 6 for considerable level of resistance and other 10 for moderate level of resistance. At the booting stage, on the other hand, a total of 18 accessions were highly resistant in addition to other 3 for considerable level of resistance and other 5 for moderate level of resistance. A total of 42 accessions with high to moderate level of resistance were distributed across 16 countries in Asia in addition to each one for Madagascar and USA. The classification of landraces based on the present protocol for screening resistance to the insect provided fundamental information for genetics and breeding on resistance to the GRH in rice.

Loss of Resistance to <i>Nilaparvata lugens</i> May Be Due to the Low-Level Expression of <i>BPH32 </i>in Rice Panicles at the Heading Stage

The brown planthopper (BPH), Nilaparvata lugens (Stål), is the most important insect pest of rice in Asia. Host plant resistance is one of the strategies currently used to control BPH. The resistant rice cultivar Rathu Heenati (RH) carrying the BPH3 gene (recently renamed as “BPH32”) remains effective despite more than 30 years of deployment. RH has been determined to be resistant against BPH at all growth stages. However, we observed that BPH could feed on panicles but not on the leaf sheaths of RH. The resistance gene BPH32 was introduced into KDML105 through marker-assisted selection, and the introgression line UBN03078 was developed. This rice line was used to observe the patterns of target gene’s regulation. A low-level expression of BPH32 on panicles has been hypothesized to cause susceptibility in UBN03078 at the heading stage. Findings from our gene expression analysis support the hypothesis that the resistance gene was down regulated in the uppermost internodes compared with the leaf sheaths of the heading rice plant. This phenomenon may allow BPH to feed on the panicles of the resistant plants, but this requires further investigation.

Field Efficacy of Certain New Insecticides against Major Insect Pests of Rice at Manipur

Field experiment conducted during kharif, 2012 and 2013 at the Rice Research Farm of the College of Agriculture, Central Agricultural University, Imphal evaluated the efficacy of certain new insecticides against the rice pests viz., Asian gall fly (Orseolia oryzae Wood-Mason), yellow stem borer (Scirpophaga incertulas Walker), leaf folder (Cnaphalocrocis medinalis Guenee) and whorl maggot (Hydrellia philippina Ferino). Against the gall fly, thiamethoxam 25 WG @ 25 g a.i. ha1 was found effective. This was followed by imidacloprid 70 WG @ 50 g a.i. ha−1(4.40% SS) and acephate 50 + imidacloprid 1.8% (Lancergold) 51.8 SP @ 500 g a.i. ha−1 but insignificantly. Flubendiamide 39.35 SC @ 24 g a.i. ha−1 was also found effective against the leaf folder and yellow stem borer with the least leaf damage (LD), dead heart (DH) and white ear head (WEH). It was followed by chlorantraniliprole 18.35 SC @ 30 g a.i.ha−1 and thiamethoxam 25 WG @ 25 g a.i. ha−1 which showed insignificant difference. Against the whorl maggot, thiamethoxam 25 WG @ 25 g a.i. ha−1 was found the best, closely followed by acephate 50% + imidacloprid 1.8%. Maximum grain yield (5.00 t ha−1) was obtained from the plots treated with flubendiamide 39.35 SC, and it was found insignificantly differing from thiamethoxam 25 WG (5.00 t ha−1), at par with acephate 50% + imidacloprid 1.8% 51.8SP (4.83 t ha−1), fipronil 5 SC (4.72 t ha−1) and flubendiamide 39.35 SC (4.68 t ha−1). Thiocloprid 21.7 SC gave the least grain yield. The net profit varied from Rs 2353 (thiacloprid 21.7 SC) to Rs. 17288 (thiamethoxam 25 WG) with the cost: benefit ratios ranging from 1: 0.45 to 1: 10.79, the minimum and maximum being with thiacloprid 21.7 SC and thiamethoxam 25 WG, respectively.

The overexpression of insect endogenous small RNAs in transgenic rice inhibits growth and delays pupation of striped stem borer (Chilo suppressalis )

The striped stem borer (SSB), Chilo suppressalis Walker, is a major rice insect pest worldwide. RNA interference (RNAi) has become a promising strategy for developing insect-resistant crops. In a previous study, five double-stranded RNAs (dsRNAs) targeting important SSB housekeeping genes were overexpressed in rice, but none of the acquired dsRNA-transgenic rice plants showed significant effects on SSB. Thirteen selected SSB endogenous small RNAs, predicted as SSB novel microRNAs (miRNAs), were overexpressed in rice using artificial miRNA (amiRNA) expression technology. Feeding tests showed that two out of 13 selected SSB novel miRNAs caused significant growth inhibition for feeding SSB larvae based on transgenic rice expression. Pupation was delayed 4 days when SSB larvae consecutively fed on transgenic rice expressing the SSB novel miRNA candidate csu-novel-miR15 (csu-15 rice). Gene expression analysis confirmed that the expression levels of at least six SSB unigenes significantly changed (i.e., were up- or down-regulated) after feeding on csu-15 rice. Our research demonstrated a novel RNAi strategy using SSB endogenous small RNAs to develop RNAi crops for pest management; this strategy is different from the common RNAi resulting from transgenic dsRNAs or amiRNAs targeting certain insect endogenous genes. © 2016 Society of Chemical Industry.

Chromosomal Location of a Recessive Red-Eye Mutant Gene in the Brown Planthopper <i>Nilaparvata lugens</i> (Stål) (Insecta: Hemiptera)

The color of compound eyes is an important biological characteristic of insects. A red eye color mutation is commonly found in the brown planthopper (BPH), Nilaparvata lugens (St&#229l) (Hemiptera: Delphacidae), a serious insect pest of rice in tropical and temperate Asia. The genetic inheritance and physiological effect of the eye color mutation in the BPH have been studied, but the location of a red gene controlling the red eye mutant phenotype on a chromosome has not been elucidated. In this study, simple sequence repeats (SSRs), together with bulked segregant analysis (BSA), was performed to identify and map the location of the red gene. A total of 387 SSR markers distributed throughout the BPH autosome were used to survey two bulked DNA samples. Samples were generated from 29 brown-eyed and 29 red-eyed individuals derived from an F2 generation of a cross between brown-eyed wild type and red-eyed mutant colonies. The SSR marker BM20 was shown to be associated with the red eye mutant phenotype. Ninety-five offspring of the F2 generation were then used to map the gene. The present study constitutes the discovery of the location of the red gene, which may lead to the acquisition of the genetic determinant of the compound eye color mutation in BPH.

Mapping of QTLs conferring resistance in rice to brown planthopper, Nilaparvata lugens

AbstractBrown planthopper (BPH), Nilaparvata lugens Stål (Hemiptera: Delphacide), is a destructive insect pest of rice, Oryza sativa L. (Poaceae), in rice‐producing areas worldwide. Host plant resistance is a major aspect of managing this pest. In this study, a mapping population consisting of 150 F3 lines, derived from a cross of MR276 and Rathu Heenati, was used to detect and analyse quantitative trait loci (QTLs) for the resistance to BPH. Composite Interval Mapping (CIM) was used for QTL detection. In total 10 QTLs controlling BPH resistance were mapped on chromosomes 1, 3, 6, 7, 9, 10, and 12. Four QTLs – qBph‐1‐1, qBph‐3‐1, qBph‐6‐1, and qBph‐7‐1 – were mapped on chromosomes 1, 3, 6, and 7 in the standard seedbox screening test, explaining 41% of the phenotypic variance. Two QTLs, qBph‐6‐1 and qBph‐9‐1, were detected on chromosomes 6 and 9 in the honeydew test, accounting for 32% of the total phenotypic variance. Moreover, four QTLs – qBph‐3‐1, qBph‐6‐1, qBph‐10‐1, and qBph‐12‐1 – were identified on chromosomes 3, 6, 10, and 12 expressing antixenosis to BPH and explaining 41% of the phenotypic variance. QTL qBph‐3‐1 was located in the chromosomal region between markers RM231 and RM3872 on chromosome 3, and QTL qBph‐6‐1 was located in the region between RM588 and RM204 on chromosome 6, indicating that these regions have a major effect in controlling the resistance to BPH in the population studied. The molecular markers linked to QTLs that are identified will be useful in the development of varieties resistant to BPH. Our study contributes to the development of genetic material for breeding programmes and marker‐assisted selection (MAS) in rice to improve BPH resistance.

A Genome-Wide Identification and Analysis of the Basic Helix-Loop-Helix Transcription Factors in Brown Planthopper, Nilaparvata lugens.

The basic helix-loop-helix (bHLH) transcription factors in insects play essential roles in multiple developmental processes including neurogenesis, sterol metabolism, circadian rhythms, organogenesis and formation of olfactory sensory neurons. The identification and function analysis of bHLH family members of the most destructive insect pest of rice, Nilaparvata lugens, may provide novel tools for pest management. Here, a genome-wide survey for bHLH sequences identified 60 bHLH sequences (NlbHLHs) encoded in the draft genome of N. lugens. Phylogenetic analysis of the bHLH domains successfully classified these genes into 40 bHLH families in group A (25), B (14), C (10), D (1), E (8) and F (2). The number of NlbHLHs with introns is higher than many other insect species, and the average intron length is shorter than those of Acyrthosiphon pisum. High number of ortholog families of NlbHLHs was found suggesting functional conversation for these proteins. Compared to other insect species studied, N. lugens has the highest number of bHLH members. Furthermore, gene duplication events of SREBP, Kn(col), Tap, Delilah, Sim, Ato and Crp were found in N. lugens. In addition, a putative full set of NlbHLH genes is defined and compared with another insect species. Thus, our classification of these NlbHLH members provides a platform for further investigations of bHLH protein functions in the regulation of N. lugens, and of insects in general.

Allelic diversity in an NLR gene BPH9 enables rice to combat planthopper variation

Brown planthopper (BPH), Nilaparvata lugens Stål, is one of the most devastating insect pests of rice (Oryza sativa L.). Currently, 30 BPH-resistance genes have been genetically defined, most of which are clustered on specific chromosome regions. Here, we describe molecular cloning and characterization of a BPH-resistance gene, BPH9, mapped on the long arm of rice chromosome 12 (12L). BPH9 encodes a rare type of nucleotide-binding and leucine-rich repeat (NLR)-containing protein that localizes to the endomembrane system and causes a cell death phenotype. BPH9 activates salicylic acid- and jasmonic acid-signaling pathways in rice plants and confers both antixenosis and antibiosis to BPH. We further demonstrated that the eight BPH-resistance genes that are clustered on chromosome 12L, including the widely used BPH1, are allelic with each other. To honor the priority in the literature, we thus designated this locus as BPH1/9 These eight genes can be classified into four allelotypes, BPH1/9-1, -2, -7, and -9 These allelotypes confer varying levels of resistance to different biotypes of BPH. The coding region of BPH1/9 shows a high level of diversity in rice germplasm. Homologous fragments of the nucleotide-binding (NB) and leucine-rich repeat (LRR) domains exist, which might have served as a repository for generating allele diversity. Our findings reveal a rice plant strategy for modifying the genetic information to gain the upper hand in the struggle against insect herbivores. Further exploration of natural allelic variation and artificial shuffling within this gene may allow breeding to be tailored to control emerging biotypes of BPH.