Wing polymorphism in Japanese and foreign strains of the brown planthopper, Nilaparvata lugens

Great variations in nymphal density and wing-form relationships occur in field populations of the brown planthopper, Nilaparvata lugens (Stål) (Homoptera: Delphacidae). When tested under uniform laboratory conditions, half of the female populations collected from 20 locations in Japan exhibited higher ratios of macropters with increasing nymphal density, but one quarter were macropterous over broad ranges of density, both types being classified as group III. Three predominantly brachypterous populations (group I) were found, even under crowded conditions and one intermediate (group II).The populations from South Asian countries, i.e. Philippines (one), Indonesia (two) and Malaysia (one) belonged to group I, but the three populations from the coastal areas of China belonged to group II. Those from Taiwan differed in responses to density; one was of group II type, and two of group III type.From these comparisons, immigration routes of N. lugens to Japan were estimated, and survival strategy of this migratory species is discussed.

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Zusammenfassung In Feldpopulationen von Nilaparvata lugens (Stål) (Homoptera: Delphacidae) gibt es grosse Variationen in der Larvendichte und in den Flügelform-Beziehungen. Unter einheitlichen Laboratoriumsbedingungen wurden diese Verhältnisse geprüft. Von 20 japanischen Herkünften zeigte die Hälfte der Weibchenpopulationen mit zunehmender Larvendichte einen höheren Macropterenanteil; ein Viertel was über einen grossen Dichtebereich macropter; beide Typen werden als Gruppe III bezeichnet. Drei Populationen wurden gefunden, die auch bei hoher Dichte vorwiegend brachypter waren (Gruppe I). Einer Zwischengruppe (II) gehörte eine einzige Population an.Die Populationen aus südasiatischen Ländern (1 aus den Philippinen, 2 aus Indonesien un 1 aus Malaysia) gehörten zu Gruppe I, die 3 Populationen aus den Küstenregionen von China jedoch zu Gruppe II. Die Populationen aus Taiwan unterschieden sich in der Reaktion auf die Dichte: 1 gehörte zu Gruppe II and 2 zu Gruppe III.Von diesen Daten werden Einwanderungswege von N. lugens nach Japan abgeleitet und die Überlebensstrategie dieser Wanderart diskutiert.

     

Inheritance of body color in the brown planthopper, Nilaparvata lugens

The segregation frequencies of color phenotypes of F₁, F₂, and backcross progenies revealed that the body coloration of the brown planthopper, Nilaparavata lugens(Stål), exhibited multiple allelism. Monogene for color morphism exists in three allelic forms >-b ⁺ (brown or wild type), b ^o (orange) and b ^b (black). The dominance relationship was b ^b>b ⁺>b ^o. The relationship between phenotype and genotype in N. lugens was not fixed. The six possible genotypes produced eight phenotypes.

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Résumé Les fréquences de ségrégation des différentes colorations de F₁, F₂ et des croisements en retour ont montré que la coloration du corps de Nilaparvata lugens est due à un multi-allèlisme. Le monogène pour la couleur existe sous trois formes allèliques: b⁺ (brun ou sauvage), b^o (orange) et b^b (noir). Les relations de dominance étaient: b^b>b⁺>b^o. On n'a pas établi les relatios entre phénotypes et génotypes chez N. lugens. Les 6 génotypes possibles produisent 8 phénotypes.

     

Meiosis in males of the brown planthopper, Nilaparvata lugens

Meiosis in spermatocytes was studied among the three biotypes of the brown planthopper, Nilaparvata lugens (Stål). The chromosome number, morphology, and behavior of the biotypes were similar. The autosomes divided normally, reductional for the first division and equational for the second. The X chromosome had an unstable segregation behavior; it may segregate equationally or reductionally during the first division depending on its chromatid's orientation. Metaphase I plates contained 14 autosomal bivalents and an X chromosome (14_II + X). The co-oriented sister chromatids of the X chromosome moved together to either one of the poles during anaphase I, while auto-oriented sister chromatids segregated to opposite poles. Because of the anomalous segregation behaviour of the X chromosome, metaphase II plates may both contain 14_I + X chromatid, or one with only 14_I and the other with 14_I + X chromosome. Male N. lugens has a diploid chromosome number of 29.

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Zusammenfassung Die Meiose in Spermatozyten wurde in drei Biotypen von Nilaparvata lugens (Stål) studiert. Die Anzahl der Chromosomen, die Morphologie und das Verhalten der Biotypen waren ähnlich. Die Autosomen teilten in einer normalen Weise, reduzierend für die erste und äquatorial für die zweite Teilung. Das X-Chromosom hatte ein unstabiles Teilungsverhalten; es kann sich äquatorial oder aber auch reduktional trennen, je nachdem wie sich sein Chromatid orientiert hat. Die Ebenen der Metaphase I enthalten 14 autosome Bivalente und ein X-Chromosom (14_II + X). Die co-orientierten Schwester-chromatiden des X-Chromosoms bewegen sich während der Anaphase I zusammen zu einem der beiden Pole, während auto-orientierte Schwester-chromatiden sich nach entgegengesetzten Polen trennen. Wegen des ungewöhnlichen Teilungsverhaltens des X-Chromosoms, können beide Metaphase II Ebenen 14_I und X Chromatid enthalten, oder aber eine Ebene enthält 14_I und die andere 14_I + X.

     

褐飞虱体内保幼激素滴度变化及其与翅型分化的关系

用高压液相色谱及放射化学法,分别测定了褐飞虱Nilaparvata lugens 1～5龄若虫体内的保幼激素滴度与保幼激素酯酶活性变化,并用保幼激素类似物(ZR-515)进行体表点滴加以验证。结果表明,褐飞虱雌、雄4龄若虫期及雄虫的5龄若虫初期,短、长翅型间体内保幼激素滴度差异明显,可以认为该阶段是其翅型分化的关键时期。     

Allozyme variation among biotypes of the brown planthopperNilaparvata lugens in the Philippines

Allozyme variation was studied in threeNilaparvata lugens biotypes infesting specific rice varieties and a biotype infesting a weed grass,Leersia hexandra. Of the 20 enzymes inN. lugens for which activity was noted, 9 were polymorphic. Eleven enzyme loci were monomorphic for the same allele in all biotype populations; the rest were polymorphic for two or more alleles. The mean number of alleles per polymorphic locus was 2.3, while the mean number of alleles per locus was 1.5; heterozygosity ranged from 0.02 to 0.06 (biotype 1 > biotype 3 >Leersia-infesting biotype > biotype 2). Allelic frequency differences were observed in five loci among the four biotypes. However, the coefficient of genetic identity (I) of 0.99+ showed that the four biotype populations were genetically close relatives or merely populations ofN. lugens undergoing genetic differentiation. This work was partly supported by a financial grant received from the Directorate for Technical Cooperation and Humanitarian Aid, Switzerland.     

Specificity of acoustic signals and mate choice in the brown planthopper Nilaparvata lugens

Mate choice experiments were made between populations of N. lugens from the Philippines, Solomon Is. and northern Australia. Significant barriers to mating were found between the Australian insects and the other two populations. The acoustic signals of successful males in hybridisation experiments were recorded and their pulse repetition frequencies (PRFs) were compared with the mean PRF for a random sample from their own population. In crosses between insects from Australia and the Philippines or Solomon Is. succesful males were characterised by PRFs significantly different from their own populations and closer to those of the female populations in each cross than to their own. It is concluded that PRF of male calls is an important species recognition signal in N. lugens.

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Résumé La communication sexuelle de N. lugens s'effectue par signaux acoustiques transmis par le substrat. Quelques populations géographiquement définissables diffèrent par la fréquence des répétitions des impulsions (PRF) produits par les appels des mâles. Des populations des Philippines, des Iles Salomon et de l'Australie du Nord ont été étudiées.Des expériences de sélection sexuelle ont montré que des obstacles au transfert de spermatozoïdes apparaissaient dans les croisements qui impliquent un parent originaire de la population australienne. Des expériences dhybridation ont été répétées entre individus males et females de chacune des 3 populations étudiées. Le taux de succès étrait faible quand l'un des parents était originaire d'Australie. Le PRF des males de chaque croisement réussi a été déterminé et comparé au PRF moyen d'un échantillon constitué au hasard de males provenant de la même population. Pour les croisements impliquant un parent australien, le PRF des males victorieux différait de la moyenne et se rapprochait de celui des males de la population dont dérivait la female.On en a conclu que le PRF des appels males est important dans la reconnaissance spécifique de N. lugens, mais que chaque population montre un polymorphisme important pour ce caractère.

     

2006年安庆地区褐飞虱大发生特点及其原因分析

2006年褐飞虱Nilaparvata lugens Stl大发生的特点主要有:迁入虫量大、回迁峰次明显;短翅型成虫发生早、虫口高;田间种群增长迅速,全市普遍重发,局部暴发;田块间虫口差异大。分析认为导致大发生的主要原因是:丰富的初迁虫源奠定了大发生的基础;褐飞虱生物型变化,食料条件丰富;单季稻面积扩大,从食料和生境2个方面为褐飞虱发生提供利好条件;褐飞虱对主治药剂吡虫啉产生抗性,促进褐飞虱暴发。还就加强异地监测、抗药性监测、田间调查等,提出建议。     

Determination and distribution of a female-specific protein in the brown planthopper, Nilaparvata lugens Stal (Homoptera: Delphacidae)

Electrophoretic analyses of hemolymph and body or ovary homogenates from reproducing females, males, and 5th instar nymphs of the brown planthopper, Nilaparvata lugens Stal, revealed a protein band of 175 kDa in females. An immunoblot test using antibody against this protein showed a positive reaction with a 175 kDa protein from female body or ovary homogenates. It is likely that this protein in hemolymph is vitellogenin (Vg). Distribution of Vg was determined by immunofluorescence and immunogold labeling techniques. The results showed that the positive immunofluorescence reactions were present in yolk particles, the intercellular space of follicle cells, hemolymph, and the epithelial plug of ovarioles. In addition, the yeast-like symbiotes (YLS) in mycetocytes of adults and various nymphal instars as well as those free in hemolymph or entering oocytes also exhibited a positive reaction. Electron micrographs showed that immunogold particles were found most in yolk mass and YLS over other tissues. Especially the YLS in various developmental stages all contained immunogold particles, implying that the symbiote is somewhat related with production of the female-specific protein.     

Pesticide-induced susceptibility of rice to brown planthopper Nilaparvata lugens

The effects of rice plants treated with various pesticides (jingganmycin, bisultap and methamidophos) on feeding, survival rates and population growth of Nilaparvata lugens Stål (Homoptera: Delphacidae), susceptibility of the treated rice plants and amounts of free amino acids and sucrose were studied. Experiments indicated that the effects of the tested pesticides were dependent on nymphal age, pesticide and their dose and time after application. Jingganmycin at 75 g a.i. ha^–1 significantly increased the N. lugens population. Both jingganmycin and bisultap increased the survival rate of N. lugens nymphs. The feeding rate of the insects was also affected by the pesticide application, but the effect varied between nymphal age and time after application and lasted no longer than 15 d. Results clearly indicated that pesticide application increased the susceptibility of rice plants to N. lugens. Although the free amino acids in rice plants did not change with the pesticide treatments, the concentration of sucrose significantly decreased 5 d after application and the C/N ratio significantly decreased in jingganmycin treated plants 5 d and 10 d after application.     

Sensitive periods for wing development and precocious metamorphosis after precocene treatment of the brown planthopper,Nilaparvata lugens

The critical periods for juvenile hormone suppression of wing development and metamorphosis were examined in a pure brachypterous line of Nilaparvata lugens following topical application of Precocene II (PII) to various stages of the third and fourth nymphal stadia. When PII, in doses ranging from 10 pg to 100 ng, was applied to 12-h-old third or 6-h-old fourth stadium nymphs, long-wing formation (macroptery) was induced. Macropter induction ranged from 5 to 50% in females and from 30 to 50% in males, the effect being more prominent in males. The sensitive period for macropter induction lasted from the early second stadium through to day one of the fourth (penultimate) stadium. Beyond that period nymphs required sensitivity to PII and the numbers of macropters increased towards the final nymphal molt, again males were more sensitive. On the other hand, periods sensitive to PII for precocious metamorphosis induction appeared from early second stadium to 18 h after molting to the third nymphal stadium. Overlapping application of JH-III with PII at early third stadium could totally inhibit the occurrence of precocious metamorphosis and significantly rescue the macropter induction. From the data described, a scheme is presented for the control of wing development and metamorphosis by juvenile hormone, assuming two types of threshold value determining wing form and metamorphosis.     

有机稻田褐稻虱种群动态及天敌作用分析

为组建有机稻田褐稻虱Nilaparvata lugens(Stl)种群生态控制系统,系统调查实施有机耕作1年后褐稻虱种群动态,并应用生命表技术评价自然天敌的作用。结果表明,有机晚稻田中褐稻虱种群发生2个世代。高峰期分别为9月底~10月初、10月下旬,平均百丛达502.3,164.5头,种群增长率为常规稻田的31.76%。水稻移栽后天敌数量迅速回升,有机稻田中蜘蛛、捕食性天敌、寄生性天敌分别比常规稻田增长66.10%,166.67%,44.24%。将各类天敌作用相加,以"捕食及其它"、"寄生"对褐稻虱种群的控制作用最强,其EIPC值均显著高于常规稻田相应天敌因子EIPC。     

Relative contribution of genetic and environmental factors to determination of wing morphs of the brown planthopper Nilaparvata lugens

Wing dimorphism is a fascinating feature of the ability of insects to adapt to environments. The brown planthopper (BPH) Nilaparvata lugens, a serious pest of rice, can switch between the long- and short-winged morphs. It has been known that environmental factors can affect the wing morph of BPH. However, it is still unclear whether the effect of environment is dependent on BPH genetic backgrounds or not. In the present study, we established the pure-bred lineages of short- and long-winged BPHs via multigenerational selection, and we found that survival and fecundity were similar between these 2 lineages. Wing morphs of the pure-bred lineages were almost fully dependent on genetics, but independent of the environmental factors, nymphal density and rice plant stage, 2 key factors affecting BPH wing morphs. In the unselected BPH population, short- and long-winged morphs were produced depending on those 2 environmental factors, indicating the contribution of environment to wing morph. In the wing-selected lineages, 4 developmental regulated genes of wing, NlInR1, NlInR2, NlAkt, and NlFoxo were expressed stably in the short-winged adults, but almost silenced in the long-winged adults. However, all these genes were expressed normally with a similar level in both the short- and long-winged adults in an unselected population except NlFoxo. The pure-bred lineages of long- and short-winged morphs exhibited different expression patterns of wing development-regulated genes, suggesting the genetic determination of wing morphs. Effects of environmental factors on wing morphs occurred only in the genetic mix population.     

褐飞虱成虫体内磁性物质检测

地磁定向是昆虫远距离迁飞定向的重要机制之一.本研究以褐飞虱Nilaparvata lugens长翅型和短翅型成虫为研究对象,利用MPMS-7型号超导量子干涉磁强计(磁场范围为±4.8 mA/m,温度范围为1.9 ～ 400 K)检测虫体内的磁性物质,明确其体内的分布状况.结果表明:褐飞虱长翅型雄成虫整个虫体的温度退磁曲...     

Molecular characterization,tissue and developmental expression profiles of cryptochrome genes in wing dimorphic brown planthoppers,Nilaparvata lugens

Cryptochromes (CRYs) are blue and UV light photoreceptors, known to play key roles in circadian rhythms and in the light‐dependent magnetosensitivity of insects. Two novel cryptochrome genes were cloned from the brown planthopper, and were given the designations of Nlcry1 and Nlcry2, with the accession numbers KM108578 and KM108579 in GenBank. The complementary DNA sequences of Nlcry1 and Nlcry2 are 1935 bp and 2463 bp in length, and they contain an open reading frame of 1629 bp and 1872 bp, encoding amino acids of 542 and 623, with a predicted molecular weight of 62.53 kDa and 70.60 kDa, respectively. Well‐conserved motifs such as DNA‐photolyase and FAD‐binding‐7 domains were observed in Nlcry1 and Nlcry2. Phylogenetic analysis demonstrated the proteins of Nlcry1 and Nlcry2 to be clustered into the insect's cryptochrome 1 and cryptochrome 2, respectively. Quantitative polymerase chain reaction showed that the daily oscillations of messenger RNA (mRNA) expression in the head of the brown planthopper were mild for Nlcry1, and modest for Nlcry2. Throughout all developmental stages, Nlcry1 and Nlcry2 exhibited extreme fluctuations and distinctive expression profiles. Cryptochrome mRNA expression peaked immediately after adult emergence and then decreased subsequently. The tissue expression profiles of newly emerged brown planthopper adults showed higher expression levels of CRYs in the head than in the thorax or abdomen, as well as significantly higher levels of CRYs in the heads of the macropterous strain than in the heads of the brachypterous strain. Taken together, the results of our study suggest that the two cryptochrome genes characterized in the brown planthopper might be associated with developmental physiology and migration.     

Role of rice volatiles in the foraging behaviour of the predator Cyrtorhinus lividipennis for the rice brown planthopper Nilaparvata lugens

Experiments were conducted inlaboratory to study the impacts of ricegenotypes and rice plants treated withdifferent levels of nitrogen on the predationrates of the predator, Cyrtorhinuslividipennis Reuter, for eggs of the rice brownplanthopper (BPH), Nilaparvata lugens(Stål), and their relation to the ricevolatiles. In two-choice test, the predatorfemales showed different predation rates forBPH eggs on different rice genotypes, but notfor BPH eggs on rice plants treated withdifferent levels of nitrogen. The olfactoryresponse test revealed that more femalepredators oriented to the odours from healthyrice plants compared with the plain air(control); the predator preferred plant-BPHnymph complex over healthy plants, andplant-BPH gravid female complex over plant-BPHnymph complex. Additional experimentsdemostrated that there were obvious differencesin attractiveness of the healthy plants andplant-BPH gravid female complex of various ricegenotypes, while no significant differenceswere found between rice plants treated withdifferent levels of nitrogen. The results ofpredation rates of the predator on variousvarieties and plants treated with differentlevels of nitrogen were consistent with that ofits olfactory response in 5 of the 6 casesevaluated, which showed that rice volatilesplayed an important role in the foragingbehaviour of C. lividipennis.Implications for augmenting the effectivenessof natural enemies by adjusting rice attributesand cultural practices are discussed.     

Differential gene expression in response to brown planthopper feeding in rice

Plant responses to herbivores are complex. 108 cDNA clones representing genes relating to plant responses to chewing insect-feeding, pathogen infection, wounding and other stresses were collected. Northern blot and cDNA array analysis were employed to investigate gene expression regulated by piercing-sucking insect, brown planthopper (BPH), Nilaparvata lugens (Homoptera: Dephacidae) on both the resistant and susceptible rice genotypes. After BPH feeding in rice for 72 h, the expression of most tested genes was affected. 14 genes in resistant rice variety B5 and 44 genes in susceptible MH63 were significantly up- or down-regulated. Most of the well-regulated genes were grouped in the categories of signaling pathways, oxidative stress/apoptosis, wound-response, drought-inducible and pathogen-related proteins. Those related to the flavonoid pathway, aromatic metabolidsm and the octadecanoid pathway were mostly kept unchanged or down-regulated. Our results indicate that BPH feeding induces plant responses which would take part in a jasmonic acid-independent pathway and crosstalk with those related to abiotic stress, pathogen invasion and phytohormone signaling pathways.     

A Simple Sequence Repeat- and Single-Nucleotide Polymorphism-Based Genetic Linkage Map of the Brown Planthopper,Nilaparvata lugens

In this study, we developed the first genetic linkage map for the major rice insect pest, the brown planthopper (BPH, Nilaparvata lugens). The linkage map was constructed by integrating linkage data from two backcross populations derived from three inbred BPH strains. The consensus map consists of 474 simple sequence repeats, 43 single-nucleotide polymorphisms, and 1 sequence-tagged site, for a total of 518 markers at 472 unique positions in 17 linkage groups. The linkage groups cover 1093.9 cM, with an average distance of 2.3 cM between loci. The average number of marker loci per linkage group was 27.8. The sex-linkage group was identified by exploiting X-linked and Y-specific markers. Our linkage map and the newly developed markers used to create it constitute an essential resource and a useful framework for future genetic analyses in BPH.     

Variation in feeding behaviour of Nilaparvata lugens on resistant and susceptible rice varieties

The feeding behaviour of Nilaparavata lugens was monitored on three rice varieties showing different levels of resistance in the Philippines, using a video-assisted observation method. N. lugens made more frequent, shorter probes on the moderately resistant IR46 and resistant IR62 rice varieties than on the susceptible IR22. Honeydew production was significantly lower on the resistant varieties though insect weight gains in 24 h were similar on IR46 and IR22, both being significantly greater than on the highly resistant variety.Population development, growth index and damage ratings were low on IR62 indicating antibiosis and/or non preference. When IR46 plants were infested as seedlings population increase, growth index and damage ratings were similar to those on the susceptible IR22. When infested at a later stage of plant growth the damage rating showed a moderate level of resistance though some population development was maintained, indicating antibiosis and tolerance. N. lugens started probing less frequently after surface exploration on both resistant varieties than on IR22 suggesting the presence of a resistance factor associated with the surface waxes of these varieties.

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Résumé Le comportement alimentaire de Nilaparvata lugens sur variétés de riz, sensible (IR22), partiellement résistante (IR46) et fortement résistante (IR62), a été contrôlé avec une méthode associant la vidéo à l'observation. N. lugens faisait des piqûres plus fréquentes et plus brèves sur IR46 et IR62, que sur la variété sensible. La production de miellat était significativement plus faible sur les variétés résistantes, bien que les gains de poids des insectes aient été les mêmes en 24 h sur IR46 et IR22, les deux étant significativement supérieurs à celui sur IR62.La croissance de la population, l'indice de croissance et le taux de dégâts étaient tous plus faibles sur IR62, ce qui révèle une antibiose et/ou une absence de préférence. Quand la contamination des IR46 a au lieu au stade semis, la croissance de population, l'indice de croissance et le taux de dégâts étaient semblables à ceux de la variété sensible IR22. Quand la contamination avait lieu à un stade ultérieur, le laux de dégâts révélait un niveau modéré de résistance bien qu'une certaine croissance de population se soit maintenue, ce qui révèle antibiose et tolérance.Après exploration de la surface des feuilles des deux variétés résistantes, N. lugens sondait moins fréquemment que sur IR22, ce qui laisse présumer un facteur de résistance associé aux cires superficielles de ces variétés.