Plant-mediated interactions between the rice water weevil and fall armyworm in rice

Greenhouse studies were conducted to investigate plant-mediated interactions between an above-ground and a below-ground herbivore when sharing a common host plant, rice (Oryza sativa L). Two common pests of rice were used: the rice water weevil (RWW), Lissorhoptrus oryzophilus Kuschel, as the root herbivore, and the fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) as the foliage-feeding herbivore. Rice water weevil larval performance was assessed by measuring larval density and average weight in response to different levels of defoliation by FAW larvae. The reciprocal experiment was done to evaluate FAW performance (growth rate) in response to RWW feeding. Severe defoliation by FAW decreased RWW densities by 32% and reduced larval weights by 48% compared to larvae on roots of non-defoliated plants. Effects in the converse experiments were not as strong. FAW growth rates were reduced 9–37% when feeding on rice leaves from plants damaged by RWW compared to larvae feed leaves from the no damage treatment. These reciprocal negative effects show that RWW and FAW are potential competitors when sharing a rice plant. Because RWW and FAW did not interact directly, competition was plant-mediated.     

AcMNPVie—1基因诱导的斜纹夜蛾细胞凋亡

苜蓿丫纹夜蛾核多角体病毒 (Autographacalifornicamulticapsidnucleopolyhedrovirus,AcMNPV)感染可诱导斜纹夜蛾 (Spodopteralitura)离体细胞Sl zsu 1发生典型的细胞凋亡。通过细胞松弛素 (cytochalasinD)和NH4Cl的抑制实验 ,分别排除病毒粒子结合细胞受体蛋白 ,和病毒在核内体运输过程启动细胞凋亡信号发生的可能性。RT PCR实验证实 ,病毒基因组进入了细胞核 ,极早期基因ie 1开始了转录 ;而DNA聚合酶抑制剂 (芽栖菌素 )的存在对病毒诱导的细胞凋亡程度与进程均没有明显的影响。这说明细胞凋亡的信号是先于病毒晚期复制事件启动的。单独转染AcMNPV极早期基因ie 1可诱导斜纹夜蛾离体细胞系Sl zsu 1细胞发生部分凋亡 ,转染 2 4h后出现凋亡小体 ,4 8h达到高峰。提取转染细胞的总DNA电泳 ,可检测到典型的DNA梯形条带 (DNAladder)。另外 ,AcMNPV的ie 1基因温度敏感突变株tsB82 1在非受纳温度感染细胞时 ,细胞不发生凋亡。这些结果暗示 ,在AcMNPV感染诱导的Sl zsu 1细胞凋亡中 ,ie 1基因是一个凋亡信号的直接或间接诱导因子。     

Sperm transfer during mating, movement of sperm in the female reproductive tract, and sperm precedence in the common cutworm Spodoptera litura

Abstract. Mating behaviour, sperm transfer and sperm precedence were studied in the moth Spodoptera litura (Fabr.) (Lepidoptera: Noctuidae). There existed a rhythmic, diel pattern of mating behaviour of this moth during the scotophase, presumably set with respect to an endogenous activity rhythm. Approximately 30 min after copulation had started, the formation of the corpus of the spermatophore began in the bursa copulatrix of the female moth, but full inflation of the corpus was not completed until 45–60 min after mating had started. The mature spermatophore contained about 350 eupyrene sperm bundles and a large number of individual (loose) apyrene spermatozoa. The mating status and the age of the male insect influenced the number of sperm transferred to the female within the spermatophore, and also affected the consequent fertility. There was no evidence of sperm reflux within the male tract. Within the female, dissociation of eupyrene sperm bundles was evident within the spermatophore less than 15 min after the completion of mating. Spermatozoa began to move from the bursa (in which the spermatophore is lodged) into the spermatheca 30–45 min after the end of the copulation, and the quantity of sperm in the spermatheca reached a plateau at 90 min after mating. Apyrene sperm reached the spermatheca first, followed by eupyrene sperm. Examination of total (apyrene plus eupyrene) sperm in the female tract showed that 86% of mated females received an apparently normal amount of total sperm from the male. Examination of eupyrene sperm alone showed that 81% of matings resulted in an apparently normal transfer of eupyrene sperm. A small proportion (approximately 8%) of the matings, however, were identified as transferring a clearly subnormal quantity of eupyrene sperm to the spermatheca. The eggs produced as a result of such pairings displayed much reduced fertility (about 43%) compared to those from matings confirmed to have transferred normal quantities of sperm, which showed about 92% fertility. This shows that the availability of eupyrene sperm in the spermatheca may be an important constraint on fertility in normal populations of insects. In the laboratory, S. litura females exhibited multiple matings. Of the females, 93% mated, and the mean frequency of mating was 1.69. Mating with a fertile male led to the oviposition of an increased number of eggs. This effect continued even when the female subsequently mated with an infertile male. Displacement of sperm from previous matings is known to be an important factor in the evolution of multiple mating strategies. Our results on sperm utilization by S. litura indicated that after a second mating, the sperm utilized for subsequent fertilization were almost exclusively from the last mating with little mixing. The proportion of eggs fertilized by sperm from the second mating (P₂) was calculated as 0.95, indicating almost complete sperm precedence from the last mating.     

甜菜夜蛾发生规律及其防治研究

甜菜夜蛾在福建漳州龙海每年发生9－10年,3月中下旬开始发生,4－10月份是该虫为害农作物的严重时期,其中8－9月份为全年发生危害的高峰期,通过田间药效试验,评价了不同类型的12种杀虫剂对甜菜夜蛾的防治效果,结果表明,除尽,菜喜以及米满对田间甜菜夜蛾具有较好的防效,锐颈特,杀虫单,敌杀死等药剂对田间甜菜夜蛾几乎失去防效。     

Consequences of Interspecific Competition on the Virulence and Genetic Composition of a Nucleopolyhedrovirus in Spodoptera frugiperda Larvae Parasitized by Chelonus insularis

Nucleopolyhedroviruses ( Baculoviridae ) are virulent insect pathogens that generally show a high degree of host specificity and have recognized potential as biological insecticides. Whenever viruses are applied for pest control, a proportion of the infected insects will also be parasitized by hymenopteran or dipteran parasitoids and interspecific competition for host resources will occur; the severity of such competition is likely to be modulated to a large degree by the virulence of each type of parasite. We examined the impact of parasitism by the solitary egg-larval endoparasitoid Chelonus insularis (Hymenoptera: Braconidae) on the speed of kill of nucleopolyhedrovirus-infected Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae and the pattern of host growth and virus production in infected and/or parasitized hosts. We also examined the effect of parasitism on the virulence, infectivity and genetic composition of serially passaged virus. Both parasitism and viral infection resulted in a marked reduction in host growth. When third instar larvae were dually parasitized and virus-infected, the growth rate was even more severely affected compared to parasitized larvae. There was a significant increase in virus production in larvae infected at later instars. Interspecific competition resulted in a substantial decrease in pathogen production in parasitized larvae infected at the fourth instar, but not in parasitized larvae infected at earlier instars. The serial passage experiment resulted in the appearance of four distinct genetic isolates of the virus detected by restriction endonuclease analysis. Of the three isolates that appeared in nonparasitized larvae, two showed increased virulence, expressed by mean time to death, and for one of these the infectivity, expressed as LC 50 , was reduced. One isolate that appeared in parasitized larvae (isolate D) had increased virulence and infectivity. Southern blot analysis indicated that virus isolate D was most likely generated by point mutation of a restriction site or by alterations such as duplications, deletions or by recombination of two or more genotypic variants present in the wild-type nucleopolyhedrovirus isolate. Our study provides clear evidence of interspecific competition within the host, since, depending on the timing of inoculation, adverse effects were observed upon both the parasitoid and the virus.     

杆状病毒SpltMNPVSl136基因的克隆、表达及其产物功能

计算机分析斜纹夜蛾核多角体病毒（SpltMNPV)基因组序列,发现第136个读码框基因表达产物具有病毒囊膜蛋白的基本特征,计算机预测的SL136蛋白氨基酸序列N端具有信号肽,C端具有跨膜区,N端区还有一个许多病毒融合蛋白共有的卷曲螺旋结构。通过PCR扩增,我们克隆了Sl136基因并分别构建了原核表达载体pBVSl136及重组病毒表达载体,SDS-PAGE结果表明Sl136基因在大肠杆菌和昆虫细胞中均获得了较高的表达,另外,我们还构建了一个瞬时表达载体pUCSl136。单独转染Sl-zsu-1细胞后,低pH值环境可诱导细胞发生膜融合并形成合胞体,这些实验结果表明,Sl136基因表达的产物是一个病毒膜融合蛋白。     

斜纹夜蛾核型多角体病毒BamHI—J片段序列分析

报道了斜纹夜蛾核型多角体病毒（SpltMNPV)BamHI-J片段的序列结构。该片段定位于SpltMNPV基因组25.8-29.9图单位（msp unit）,包括4个完整的开放读码框,几丁质酶基因（chiA）的3′端部分序列和一个同源区（hr）的部分序列。4个完整的读码框包括lef-8基因,杆状病毒J结构域蛋白基因（baculovirus J domain protein gene,bjdp),ORF570和ORF165。序列分离表明：ORF570与毒蛾核型多角体病毒（Lymantria dispar MNPV）的解旋酶－2基因有31％的氨基酸同源性。ORF165为SpltMNPV特有。J结构域蛋白在其他杆状病毒基因组中尚未见报道,其氨基酸序列N端存在J结构域,推断该蛋白质具有与DnaJ蛋白类似特征。lef-8基因编码的氨基酸与已报道的杆状病毒基因组中的lef-8基因编码的氨基酸具有高的同源性,且其C端具有与其他杆状病毒LEF－8类似的保守序列CIKICGIHGQKG。     

大豆对斜纹夜蛾幼虫抗性遗传的发展表达过程

采用植物数量性状遗传体系分离分析方法,通过4个感抗杂交组合研究了在网室人工接入斜纹夜蛾幼虫的条件下大豆抗斜纹夜蛾植株反应发育过程的遗传。不论P1、P2、F1、F2、F2：3多世代联合分析或单个分离世代分析,结果均表明大豆对斜纹夜蛾幼虫的抗性为两对主基因 多基因遗传模式。但在大豆生长发育的不同时期,随害虫数量的变化,其抗虫性遗传呈动态变化过程。在两对主基因充分表达日期,主基因的遗传率较高,达70.40%-99.21%,环境影响较小;多基因遗遗传率较低,为0.00%-22.29%。     

A comparison of dietary selection behaviour in larval Locusta migratoria and Spodoptera littoralis

ABSTRACT. . Final instar nymphs of the oligophagous acridid Locusta migratoria (L.) and larvae of the polyphagous noctuid Spodoptera littoralis (Boisduval) were fed for 4, 8 or 12 h, the conditioning period, on one of four artificial diets. Of these, diet PC contained 20% protein and 10% digestible carbohydrate; another, P, contained 20% protein but with the digestible carbohydrate component replaced by cellulose; a third, C, had the protein component substituted by cellulose, and the fourth, O, had both protein and digestible carbohydrate replaced. After this conditioning period, insects were given a choice of two diets, P and C, and hence an opportunity to select for the nutrients, if any, which were lacking in their previous food. Amounts eaten and selection behaviour were then recorded in detail for a total of 9 h. This paper deals with total amounts of diet eaten during the conditioning and choice periods. Spodoptera larvae were more sensitive than the locusts to being fed a nutritionally inadequate conditioning diet, and ate only small quantities of the P, C and O diets as compared with the PC diet, irrespective of the duration of conditioning. Locusts, on the other hand, when restricted to the P diet continued to eat relatively large amounts of it throughout a 12 h conditioning period. Those nymphs fed the C diet ingested large quantities (more than of the PC diet) up until 8 h, after which intake fell. When offered a choice, both species selected for the nutrients missing from the conditioning diet, even if the conditioning period had been as short as 4 h. During the first hour of choice locusts selected the P diet if they had been previously fed C and the C diet if previously fed P. Those deprived of both nutrients increased consumption of both P and C diets. Spodoptera larvae were more sensitive to prior deprivation of digestible carbohydrate than of protein. During the first hour of choice they selected the C diet if previously fed P or O but did not choose the P diet if previously fed C. In the subsequent 8 h of choice, however, a strong selection for the P diet after previous deprivation became apparent. In the locust, the selection for nutrients missing from the conditioning diet continued for the following 8 h of choice but became masked by a tendency, shown by all nymphs, to select C over P. The functional significance and possible physiological basis of all these responses is discussed.     

Insect clocks: implication in an effective pest management

Abstract

Circadian rhythms are endogenous, and synchronize biological functions at the most suited time of the day. Insects like other organism display a wide array of circadian functions, which are controlled by a central timing system, in coordination with the peripheral clocks found in many tissues. Many insect behaviours including locomotion, courtship, mating, egg laying and photoperiodism, are influenced by the circadian systems. In this mini-review, we briefly describe the involvement of circadian clocks in various physiological processes and correlate their functions in insect life, focusing on lepidopteran pests (major group of Indian crop pests) and discuss their role(s) in the development of effective pest management strategy.