Medinalis Larvae Research Articles

Gut bacterial community of Cnaphalocrocis medinalis (Guenée) (Lepidoptera: Crambidae) is driven by rice varieties

AbstractTo understand the effect of diet on gut bacteria of Cnaphalocrocis medinalis (rice leaf folder, RLF), we compared the composition and diversity of gut bacterial community in C. medinalis larvae collected from three different rice variety fields of Minghui 82 (RLF1), Youngyong 15 (RLF2) and Minghui 2155 (RLF3), using culture‐independent PCR (V3 variable region)‐denaturing gradient gel electrophoresis (PCR‐DGGE) methods and hypervariable region (V4) of 16S rRNA sequenced by Illumina HiSeq platform. The DGGE result showed that the bacteria genera Asaia, Bacillus, Stenotrophomonas, Achromobacter and Serratia coexisted in the guts of RLF1, RLF2 and RLF3, while Cedecea, Burkholderia and Acinetobacter coexisted in the guts of RLF2 and RLF3. However, only the genus Enterococcus existed in the guts of RLF1, and Pantoea, Wolbachia and Tumebacillus in RLF3 larvae. A total of 25 bacterial phyla, 48 classes, 127 orders, 223 families, and 406 genera were identified when using 16s RNA sequencing, with 35 genera coexisted in RLF1, RLF2 and RLF3 larval guts, while 83, 36, 141 unique genera existed in RLF1, RLF2 and RLF3, respectively. The indices of ACE and Shannon were not significantly different among RLF1, RLF2 and RLF3. The dominant bacterial taxa were Proteobacteria, Bacteroidetes and Firmicutes at the phylum level, and Acinetobacter and Wolbachia at the genus level. The relative genus abundance for the genera with relative abundance (≥0.01) was significantly different among RLF1, RLF2 and RLF3. The findings indicated that different rice varieties had significant effects on the relative abundance of gut bacteria in RLF, which could provide new insights into the relationship between insect gut bacteria and their associated host plants.

Defense Responses of Different Rice Varieties Affect Growth Performance and Food Utilization of Cnaphalocrocis medinalis Larvae

Rice leaf folder, Cnaphalocrocis medinalis (Guenée), is one of the most serious pests on rice. At present, chemical control is the main method for controlling this pest. However, the indiscriminate use of chemical insecticides has non-target effects and may cause environmental pollution. Besides, leaf curling behavior by C. medinalis may indirectly reduce the efficacy of chemical spray. Therefore, it is crucial to cultivate efficient rice varieties resistant to this pest. Previous studies have found that three different rice varieties, Zhongzao39 (ZZ39), Xiushui134 (XS134), and Yongyou1540 (YY1540), had varying degrees of infestation by C. medinalis. However, it is currently unclear whether the reason for this difference is related to the difference in defense ability of the three rice varieties against the infestation of C. medinalis. To explore this issue, the current study investigated the effects of three rice varieties on the growth performance and food utilization capability of the 4th instar C. medinalis. Further, it elucidated the differences in defense responses among different rice varieties based on the differences in leaf physiological and biochemical indicators and their impact on population occurrence. The results showed that the larval survival rate was the lowest, and the development period was significantly prolonged after feeding on YY1540. This was not related to the differences in leaf wax, pigments, and nutritional components among the three rice varieties nor to the feeding preferences of the larvae. The rate of superoxide anion production, hydrogen peroxide content, and the activity of three protective enzymes were negatively correlated with larval survival rate, and they all showed the highest in YY1540 leaves. Compared to other tested varieties, although the larvae feeding on YY1540 had higher conversion efficiency of ingested food and lower relative consumption rate, their relative growth was faster, indicating stronger food utilization capability. However, they had a lower accumulation of protein. This suggests that different rice varieties had different levels of oxidative stress after infestation by C. medinalis. The defense response of YY1540 was more intense, which was not conducive to the development of the larvae population. These results will provide new insights into the interaction mechanism between different rice varieties and C. medinalis and provide a theoretical basis for cultivating rice varieties resistant to this pest.

Toxicity of insecticides to wolf spider (Pardosa pseudoannulata) and rice leaf folder (Cnaphalocrocis medinalis): assessing the risk of insecticides on spiders in the rice ecosystem

Chemical insecticides complemented with the natural enemies result in successful pest management in crop fields. Hence, knowing the impact of insecticides on natural enemies present in the rice ecosystem is essential. The wolf spider (Pardosa pseudoannulata), a predator of plant hoppers and young larva of leaf folders and stem borers in rice ecosystem, plays an important role in pest suppression. The effect of certain efficacious insecticides, commonly used in rice on P. pseudoannulata through contact toxicity was evaluated and compared with its toxicity to rice leaf folder (Cnaphalocrosis medinalis). Calculations of median lethal doses (LD50) for adult spiders revealed deltamethrin as a highly toxic chemical with an LD50 of 0.055 × 10−3 µg spider−1 followed by clothianidin (0.001 µg spider−1) at 48 h after treatment. Chlorantraniliprole was found to be highly toxic to C. medinalis larvae (LD50 = 0.001 µg larvae−1) followed by deltamethrin (0.009 µg larvae−1). Based on the risk assessment estimator selectivity ratio, which compares the LD50 of pest and predator, acephate and chlorantraniliprole were found to be safe by causing low mortality. However, when the LD90 of the pest was subjected to probit substitution, acephate, and chlorpyrifos were relatively less toxic to the predator. The hazard ratio, which takes into account the realistic field dose, revealed that chlorantraniliprole and acephate were safe for P. pseudoannulata. Most of the insecticides commonly used in agriculture negatively affect spiders, with few exceptions like chlorantraniliprole and acephate with minimum contact toxicity.

Pathogenicity of Beauveria bassiana (Balsamo) Vuillemin Isolate (TNAU ENT BB1) Against Rice Leaf Folder, Cnaphalocrocis medinalis (Guenee) in In-vitro (Laboratory) Conditions

Rice productivity is impaired by sucking, leaf feeding and borer insect pests. Among the leaf feeders, rice leaf folder Cnaphalocrocis medinalis (Guenee) cause significant yield loss. The non-chemical insect pest management is gaining momentum among farmers, and biocontrol management is one of the essential components. The efficacy of entomopathogenic fungi Beauveria bassiana (Balsamo) Vuillemin isolate against C. medinalis was studied using the laboratory culture maintained in rice leaves. Different concentrations of B. bassiana were applied topically on the second instar C. medinalis larvae. The mortality observations were recorded at 48 hrs intervals from the third day and continued up to 11 days. The highest mortality of 78.33% was observed at concentration 1×108 conidia/ml, and the lowest mortality of 36.67% was observed at concentration 1×103 conidia/ml. The determined median lethal concentration (LC50) of B. bassiana (Balsamo) Vuillemin isolate against C. medinalis is 5.44 x 105 conidia/ml.

The Gut Microbiota Composition of Cnaphalocrocis medinalis and Their Predicted Contribution to Larval Nutrition.

Intestinal bacterial flora plays an important role in the nutrition, physiology, and behavior of herbivorous insects. The composition of gut microbiota may also be affected by the food consumed. Cnaphalocrocis medinalis is an oligophagous pest, feeds on rice leaves almost exclusively and causes serious damage to rice in Asian countries. Using antibiotic treatment and metagenome sequencing, we investigated the influence of the food sources (rice and maize seedlings) on the structure and functions of intestinal bacteria of C. medinalis. Firstly, food utilization indices, relative growth rate (RGR), relative consumption rate (RCR), efficiency of conversion of ingested food (ECI), and efficiency of conversion of digested food (ECD), were all significantly adversely affected in the antibiotic treatment eliminating gut bacteria, showing that the microbiota loading in the gut were essential for the larva growth and development of C. medinalis. Further, metagenome sequencing revealed that different diets caused a variation in gut microbiota composition of C. medinalis, indicating that the gut microbiota were in part driven by the diet provided. However, the larvae of C. medinalis hosted a core microbial community in the gut, which was independent from the diets changing. The dominant bacteria in the two feeding groups were highly consistent in the gut of C. medinalis larvae, with the gut bacterial community dominated by Firmicutes at the phylum level, Enterococcus at the genus level, Enterococcus sp. FDAARGOS-375, E. casseliflavus, E. gallinarum, and E. sp. CR-Ec1 accounted for more than 96% of the gut microbiota. Functional prediction analysis demonstrated that gut bacteria encoded a series of metabolism-related enzymes involved in carbohydrate metabolism and amino acid synthesis. Carbohydrate metabolism was the most enriched function in both groups and was more abundant in rice feeding group than in maize feeding group. The core dominant Enterococcus species possessed complete pathways of 14 carbohydrates metabolism, 11 amino acids biosynthesis, and two vitamins synthesize, implied to contribute an essential role to the nutrition intake and development of C. medinalis. Finally, the study may provide an in-depth analysis of the symbiont-host co-adaptation and new insights into the management of C. medinalis.

Exogenous Copper Application for the Elemental Defense of Rice Plants against Rice Leaffolder (Cnaphalocrocis medinalis).

Metals that accumulate in plants may confer protection against herbivorous insects, a phenomenon known as elemental defense. However, this strategy has not been widely explored in important crops such as rice (Oryza sativa L.), where it could help to reduce the use of chemical pesticides. Here, we investigated the potential of copper (Cu) and iron (Fe) micronutrient supplements for the protection of rice against a major insect pest, the rice leaffolder (Cnaphalocrocis medinalis). We found that intermediate levels of Cu (20 μM CuSO4) and high concentrations of Fe (742 μM Fe) did not inhibit the growth of C. medinalis larvae but did inhibit rice root growth and reduce grain yield at the reproductive stage. In contrast, high levels of Cu (80 μM CuSO4) inhibited C. medinalis larval growth and pupal development but also adversely affected rice growth at the vegetative stage. Interestingly, treatment with 10 μM CuSO4 had no adverse effects on rice growth or yield components at the reproductive stage. These data suggest that pest management based on the application of Cu may be possible, which would be achieved by a higher effective pesticide dose to prevent or minimize its phytotoxicity effects in plants.

Docking-based generation of antibodies mimicking Cry1A/1B protein binding sites as potential insecticidal agents against diamondback moth (Plutella xylostella).

Broad use of insecticidal Cry proteins from Bacillus thuringiensis in biopesticides and transgenic crops has resulted in cases of practical field resistance, highlighting the need for novel approaches to insect control. Previously we described an anti-Cry1Ab idiotypic-antibody (B12-scFv) displaying toxicity against rice leafroller (Cnaphalocrocis medinalis) larvae, supporting the potential of antibodies for pest control. The goal of the present study was to generate insecticidal antibodies against diamondback moth (Plutella xylostella) larvae. Four genetically engineered antibodies (GEAbs) were designed in silico from B12-scFv using three-dimensional (3D) structure and docking predictions to alkaline phosphatase (ALP) as a Cry1Ac receptor in P. xylostella. Among these GEAbs, the GEAb-dVL antibody consisting of two light chains had overlapping binding sites with Cry1A and Cry1B proteins and displayed high binding affinity to P. xylostella midgut brush border membrane (BBM) proteins. Proteins in BBM identified by pull-down assays as binding to GEAb-dVL included an ABC transporter and V-ATPase subunit A protein. Despite lacking the α-helical structures in Cry1A that are responsible for pore formation, ingestion of GEAb-dVL disrupted the P. xylostella larval midgut epithelium and resulted in toxicity. Apoptotic genes were activated in gut cells upon treatment with GEAb-dVL . This study describes the first insecticidal GEAb targeting P. xylostella by mimicking Cry proteins. Data support that GEAb-dVL toxicity is associated to activation of intracellular cell death pathways, in contrast to pore-formation associated toxicity of Cry proteins. This work provides a foundation for the design of novel insecticidal antibodies for insect control. © 2021 Society of Chemical Industry.

Cloning, Characterization, and RNA Interference Effect of the UDP-N-Acetylglucosamine Pyrophosphorylase Gene in Cnaphalocrocis medinalis.

The rice leaf folder, Cnaphalocrocis medinalis is a major pest of rice and is difficult to control. UDP-N-acetylglucosamine pyrophosphorylase (UAP) is a key enzyme in the chitin synthesis pathway in insects. In this study, the UAP gene from C. medinalis (CmUAP) was cloned and characterized. The cDNA of CmUAP is 1788 bp in length, containing an open reading frame of 1464 nucleotides that encodes 487 amino acids. Homology and phylogenetic analyses of the predicted protein indicated that CmUAP shared 91.79%, 87.89%, and 82.75% identities with UAPs of Glyphodes pyloalis, Ostrinia furnacalis, and Heortia vitessoides, respectively. Expression pattern analyses by droplet digital PCR demonstrated that CmUAP was expressed at all developmental stages and in 12 tissues of C. medinalis adults. Silencing of CmUAP by injection of double-stranded RNA specific to CmUAP caused death, slow growth, reduced feeding and excretion, and weight loss in C. medinalis larvae; meanwhile, severe developmental disorders were observed. The findings suggest that CmUAP is essential for the growth and development of C. medinalis, and that targeting the CmUAP gene through RNAi technology can be used for biological control of this insect.

Genomic and phenotypic evaluation of rice susceptible check TN1 collected in Taiwan

BackgroundTaichung Native 1 (TN1), a variety of rice (Oryza sativa L.) developed in Taiwan, has played a key role in the green revolution of this major staple crop because of its semi-dwarf characteristics. Due to its susceptibility, it has been used as a susceptibility indicator in rice insect and pathogen resistance studies worldwide. While within-variety differences have been reported for agronomic traits in other rice varieties, no study has addressed the within-variety consistency of pathogen and insect susceptibility of TN1, which would influence the result interpretation of plant-pest interaction studies. Therefore, the objective of this study was to evaluate the genomic consistency and to assess a range of agronomic and insect susceptibility traits in three representative accessions of TN1 in Taiwan.ResultsAmong these three accessions, two were identical across 43,325 genome-wide single nucleotide polymorphisms (SNPs) while the third one differed at four SNPs. Of the three accessions of TN1, there were minor differences in seed length, seed breadth, length/width ratio, number of leaves and tillers, and number of unfilled seeds. Besides, there was no effect on relative growth rate of Cnaphalocrocis medinalis larvae fed on the three accession sources. Furthermore, there is no different on plant susceptibility among these three accessions against C. medinalis and Nilaparvata lugens.ConclusionOur study indicates that it is appropriate to use TN1 in Taiwan to test for rice insect susceptibility as it yields consistent results.

Evaluation of the entomopathogenic fungi as a non-traditional control of the rice leaf roller, Cnaphalocrocis medinalis (Guenee) (Lepidoptera: Pyralidae) under controlled conditions

The rice leaf roller or leaf folder, Cnaphalocrocis medinalis (Guenee) (Lepidoptera: Pyralidae), is a serious pest of rice crop in Pakistan. The present study was carried out to evaluate the virulence of the entomopathogenic fungi (EPF) Beauveria bassiana, Verticillium lecanii, and Metarhizium anisopliae against the third instar of C. medinalis larvae. Larvae were exposed to fungi under controlled conditions at the available commercial concentration (1 × 108 conidia ml−1). The results showed 73.33, 57.78, and 74.44% mortality rates in the in vitro assay and 56.67, 41.11 and 52.78% in the greenhouse assay of B. bassiana, V. lecanii, and M. anisopliae, respectively. The maximum mycosis from cadavers of C. medinalis was observed at B. bassiana treatment in the in vitro assay (70%) and in the greenhouse assay (53.78%). The maximum sporulation from C. medinalis cadavers was observed at B. bassiana treatment in the in vitro assay (144.67 conidia ml−1) and in greenhouse assay (96.67 conidia ml−1). These results favor the alternative use of EPF in organic rice production for management of C. medinalis.

Defensive responses of rice cultivars resistant to Cnaphalocrocis medinalis (Lepidoptera: Crambidae)

Cnaphalocrocis medinalis (Guenee) (Lepidoptera: Crambidae) is an economically important pest of rice, Oryza sativa L. (Poaceae), throughout Asia, where damage caused by larvae, particularly during grain-filling stages, significantly increases yield losses. There is, therefore, a pressing need to develop cultivars that are resistant to C. medinalis. In this study, we assessed growth and mortality of first and third instar C. medinalis larvae fed on six rice cultivars that had previously been identified as resistant to the pest, and we quantified production of defense enzymes in plants exposed to herbivory. We found that mortality rates were highest in larvae fed on the resistant cultivars Baiqiaowan, Sasanishiki, Qingliu, and Kasalasu, while relative growth rates were lower for larvae fed on Baiqiaowan and Qingliu. Higher levels of phenylalanine ammonia lyase were expressed in the resistant cultivars. Qingliu plants exposed to herbivory by C. medinalis produced higher levels of jasmonyl isoleucine and salicylic acid (SA) than plants of the susceptible cultivar TN1, and levels of SA in Qingliu plants were intrinsically higher prior to feeding by C. medinalis.

Fabrication of a hollow mesoporous silica hybrid to improve the targeting of a pesticide

Nanomaterials offer a great opportunity to develop new strategies for designing stimuli-responsive controlled release formulations (CRFs) of pesticides. In this study, a pH sensitive controlled release system, poly(glycidyl methacrylate-co-acrylic acid) (P(GMA-AA)) grafted hollow mesoporous silica (HMS@P(GMA-AA) was fabricated. HMS was fabricated using a hard template and functionalized with 3-(trimethoxysilyl)propyl methacrylate. Then, P(GMA-AA) was grafted onto HMS by seeded precipitation polymerization. Abamectin (aba) was selected as the model pesticide to test the pH-sensitivity property. Detailed investigations showed that Aba@HMS@P(GMA-AA) exhibited a high pesticide-loading efficiency (33 wt%) and superior stability. The release of Aba from Aba@HMS@P(GMA-AA) was pH-dependent. In addition, Aba@HMS@P(GMA-AA) showed a strong combination with rice leaves, mainly benefitting from its low contact angle and high adhesion work on leaves. Bioactivity studies in a greenhouse and the field indicated that Aba@HMS@P(GMA-AA) was more toxic than Aba emulsifiable concentrate (Aba-EC) in controlling rice pest Cnaphalocrocis medinalis (Guénee) larvae, and it possessed long-term efficacy in practice. Importantly, there was no obvious influence on the growth of rice seedlings treated with Aba@HMS@P(GMA-AA). The results suggest that the proposed controlled release system is a promising candidate for the management of pests.

Adult oviposition preferences and larval performance of rice leaf folder, Cnaphalocrocis medinalis on rice and non-rice graminaceous plants

The rice leaf folder, Cnaphalocrocis medinalis Guenee (Lepidoptera: Pyralidae), occurs throughout southeast and northeast Asia, and has a broad host range including graminaceous crops and weeds. Unraveling the relationship between adult oviposition preference and offspring performance is central to understanding the evolution of plant–insect interactions. In the present study, we examined oviposition behavior and larval performance of the C. medinalis on rice plants and non-rice graminaceous plants. Using choice oviposition experiments, female C. medinalis moths preferred rice volatiles, and laid significantly more eggs on the leaves of rice plants than non-rice graminaceous plants. Larval performance, as assayed by host plant selection rate, and host suitability, were evaluated by using multi-choice experiments and life-table analysis, respectively. Larval host selection experiments showed that the younger C. medinalis larvae (1st and 2nd instar) exhibited a stronger ability to identify rice hosts compared to non-rice graminaceous plants than older larvae (3rd to 5th instar). The results of life-table studies showed that C. medinalis developed and grew faster on rice plants than on non-rice graminaceous plants. In particular, the graminaceous crop, sugarcane Saccharum officinarum, and graminaceous weeds Miscanthus sinensis and Setaria viridis, prevented the development and ovipositing of C. medinalis. Our results showed the strong preference that C. medinalis adults had to oviposit and larvae had to develop on rice and this was highly consistent within the population tested. This indicated that oviposition preference of female C. medinalis moths might play an important role in larval host identification between rice plants and non-rice graminaceous plants.

Midgut transcriptomal response of the rice leaffolder, Cnaphalocrocis medinalis (Guenée) to Cry1C toxin.

Cnaphalocrocis medinalis (Guenée) is one of the important insect pests in rice field. Bt agents were recommended in the C. medinalis control and Bt rice is bred as a tactic to control this insect. However, the tolerance or resistance of insect to Bt protein is a main threat to the application of Bt protein. In order to investigate the response of C. medinalis transcriptome in defending a Cry1C toxin, high-through RNA-sequencing was carried in the C. medinalis larvae treated with and without Cry1C toxin. A total of 35,586 high-quality unigenes was annotated in the transcriptome of C. medinalis midgut. The comparative analysis identified 6,966 differently expressed unigenes (DEGs) between the two treatments. GO analysis showed that these genes involved in proteolysis and extracellular region. Among these DEGs, carboxylesterase, glutathione S-transferase and P450 were differently expressed in the treated C. medinalis midgut. Furthermore, trypsin, chymotrypsin, and carboxypeptidase were identified in DEGs, and most of them up-regulated. In addition, thirteen ABC transporters were downregulated and three upregulated in Cry1C-treated C. medinalis midgut. Based on the pathway analysis, antigen processing and presentation pathway, and chronic myeloid leukemia pathway were significant in C. medinalis treated with Cry1C toxin. These results indicated that serine protease, detoxification enzymes and ABC transporter, antigen processing and presentation pathway, and chronic myeloid leukemia pathway may involved in the response of C. medinalis to Cry1C toxin. This study provides a transcriptomal foundation for the identification and functional characterization of genes involved in the toxicity of Bt Cry protein against C. medinalis, and provides potential clues to the studies on the tolerance or resistance of an agriculturally important insect pest C. medinalis to Cry1C toxin.

Sublethal effects of four insecticides on folding and spinning behavior in the rice leaffolder, Cnaphalocrocis medinalis (Guenée) (Lepidoptera: Pyralidae).

The rice leaffolder, Cnaphalocrocis medinalis, is an important rice pest. The sublethal effects of chlorpyrifos, chlorantraniliprole, emamectin benzoate and spinosad were investigated on the folding and spinning behaviors of third- to fifth-instar C. medinalis larvae (L3 - L5) after insecticidal exposure of the second instar. A 25% lethal concentration (LC25 ) of chlorpyrifos prolonged the leaf selection time of L5, and reduced the number of binds per primary fold for L4 and L5. An LC10 of chlorantraniliprole reduced the number of binds per primary fold for L4 and increased the number of head swings per bind for L5. An LC10 of emamectin benzoate shortened the primary fold length for L5 and decreased the number of head swings per primary fold for L3 and L4 and the number of head swings per bind for L3, while an LC25 of emamectin benzoate shortened the fold length per 24 h for L5 and folding time for L3. An LC10 of spinosad lowered the fold length per 24 h and the number of head swings for L5. An LC25 of spinosad prolonged leaf selection time, and decreased primary fold length, binds per primary fold, binds per fold and fold length per 24 h in L5. Emamectin benzoate and spinosad exerted stronger sublethal effects on the folding and spinning behavior of C. medinalis than chlorpyrifos and chlorantraniliprole. These results provide better understanding of the sublethal effects of interactions of insecticides on C. medinalis. © 2017 Society of Chemical Industry.

Laboratory evaluation of transgenic Bt rice resistance against rice leaf roller, Cnaphalocrocis medinalis

Pest resistance of 8 transgenic Bt rice events with a synthetic cry1Ac gene linked to rice rbcS-tp sequence were assessed under laboratory conditions. Bioassays were conducted with neonates and third instar larvae of Cnaphalocrocis medinalis, which is a significant pest of rice in Asia. C. medinalis larvae were shown to be susceptible to all eight events, even though there were differences between the causes of death. The results differed between developmental stages of the larvae, despite the fact that all 8 events led to high mortalities. Neonates displayed feeding avoidance and death by starvation on six Bt rice events. In the case of third instar larvae however, only two events resulted in feeding avoidance. Nevertheless, all Bt rice events were shown to be highly effective against C. medinalis larvae in laboratory conditions. These results may be a significant foundation for the evaluation of improved transgenic Bt rice.

Identification of Genes Putatively Involved in Chitin Metabolism and Insecticide Detoxification in the Rice Leaf Folder (Cnaphalocrocis medinalis) Larvae through Transcriptomic Analysis.

The rice leaf roller (Cnaphalocrocis medinalis) is one of the most destructive agricultural pests. Due to its migratory behavior, it is difficult to control worldwide. To date, little is known about major genes of C. medinalis involved in chitin metabolism and insecticide detoxification. In order to obtain a comprehensive genome dataset of C. medinalis, we conducted de novo transcriptome sequencing which focused on the major feeding stage of fourth-instar larvae, and our work revealed useful information on chitin metabolism and insecticide detoxification and target genes of C. medinalis. We acquired 29,367,797 Illumina reads and assembled these reads into 63,174 unigenes with an average length of 753 bp. Among these unigenes, 31,810 were annotated against the National Center for Biotechnology Information non-redundant (NCBI nr) protein database, resulting in 24,246, 8669 and 18,176 assigned to Swiss-Prot, clusters of orthologous group (COG), and gene ontology (GO), respectively. We were able to map 10,043 unigenes into 285 pathways using the Kyoto Encyclopedia of Genes and Genomes Pathway database (KEGG). Specifically, 16 genes, including five chitin deacetylases, two chitin synthases, five chitinases and four other related enzymes, were identified to be putatively involved in chitin biosynthesis and degradation, whereas 360 genes, including cytochrome P450s, glutathione S-transferases, esterases, and acetylcholinesterases, were found to be potentially involved in insecticide detoxification or as insecticide targets. The reliability of the transcriptome data was determined by reverse transcription quantitative PCR (RT-qPCR) for the selected genes. Our data serves as a new and valuable sequence resource for genomic studies on C. medinalis. The findings should improve our understanding of C. medinalis genetics and contribute to management of this important agricultural pest.

Effects of Dietary Additives in Artificial Diets on Survival And Larval Development ofCnaphalocrocis medinalis(Lepidoptera: Crambidae)

Cnaphalocrocis medinalis (Guenée, 1854) (Lepidoptera: Crambidae) is an important defoliating insect of rice crops in Asia, and is difficult to rear on artificial diets. The effects of dietary additives in artificial diets on survival and larval growth of C. medinalis were evaluated. Antibiotics, ascorbic acid and vitamin mixture in the medium were indispensable for the survival and growth of C. medinalis larvae. The neonates of C. medinalis did not survive for 5 days on the artificial diets that lacked antibiotics and an antioxidant, and they did not develop to the pupal stage on the diets without the addition of vitamin mixtures. Addition of antibiotics, antioxidant and vitamins at a low level facilitated larval survival and growth. Supplementation with a vitamin mixture promoted larval growth and shortened the duration of larval development. Additions of cholesterol, and sucrose to the artificial diets improved the development of C. medinalis larvae, but excessive amounts of cholesterol and sucrose resulted in inhibition of larval growth. Incorporation of rice or corn leaf powder and plant oils increased larval mortality, and reduced pupation. The addition of Wesson's salt to the artificial diet did not improve larval survival and growth. Therefore, leaf powder, plant oils and Wesson's salt could be omitted from the medium. In addition, the water content had significant effects on larval survival and growth of C. medinalis. Eighty percent water content was the most favorable for larval development, lesser or greater proportions were disadvantageous.

Effect of oil-formulated Metarhizium anisopliae and Beauveria bassiana against the rice leaffolder Cnaphalocrocis medinalis Guenée (Lepidoptera: Pyralidae)

The rice leaffolder (RLF), Cnaphalocrocis medinalis (Guenée) (Lepidoptera: Pyralidae), has become a major pest of rice in tropical Asia. The virulence of seven fungal isolates of Metarhizium anisopliae and Beauveria bassiana to third-instar C. medinalis was tested in initial screening bioassay by application of conidia at the concentration of 1 × 108 conidia/ml. Among the tested B. bassiana, MTCC7690 produced 83% mortality with shorter lethal time (LT50) of 4.64 days (4.51–4.76) and MTCC4104 of M. anisopliae produced 79% mortality with shorter lethal time (LT50) of 4.88 days (4.66–4.95). Further, the M. anisopliae MTCC 4104 and the B. bassiana MTCC7690 were formulated in the canola oil and were tested against the C. medinalis larvae at different concentration (1 × 103–1 × 108 conidia/ml). The mortality of the larvae was dose-dependent and the oil-formulated B. bassiana MTCC7690 conidia was highly virulent isolate with lower LC50 of 9.09 × 104 conidia/ml followed by oil-formulated M. anisopliae MTCC4104 conidia with LC50 of 6.08 × 105 conidia/ml. The oil-formulated effective isolates were tested with second to fourth larval instar and significant differences in mortality among the larval stages were obtained. Also, difference significant in lethal time with shorter lethal time was recorded in second instar larva. The effective canola oil-formulated isolates are known to significantly reduce the longevity of male and female than untreated controls. The significant reduction in the number of eggs laid by the fungi-treated female than untreated control was recorded.

Effects of Nitrogen Fertilizer and Magnesium Manipulation on the <I>Cnaphalocrocis medinalis</I> (Lepidoptera: Pyralidae)

The rice leaffolder, Cnaphalocrocis medinalis Guenee (Lepidoptera: Pyralidae), is a rice pest that is prone to outbreaks when high levels of nitrogen (N) fertilizer are applied to rice. The larvae feed by scraping the mesophyll cells of leaves, which are mainly composed of chloroplasts containing significant levels of elemental magnesium (Mg). To determine the cause of N fertilizer-induced rice leaffolder outbreaks and the effects of Mg and Mg uptake on the rice leaffolder, the changes in the life history traits and biochemistry of C. medinalis larvae feeding on rice leaves treated with different Mg and N concentrations were investigated in this study. The results showed that foliar treatment using different Mg concentrations under hydroponic culture conditions significantly decreased the developmental duration (days) (DD) of the larvae and pupae but did not influence the pupation rate or adult emergence rate. The number of eggs laid by adult females and the protein content and total sugar content in the larvae and pupae significantly increased with increasing Mg concentrations. Under soil culture conditions, the DD for the larvae and number of eggs laid by adult females significantly increased with increasing nitrogen fertilizer levels, but the applied fertilizer did not influence the DD in the pupae, pupation rate, or adult emergence rate. In contrast, the DD for adults decreased with increased fertilizer levels. In hydroponic culture, Mg in the culture solution and Mg foliar sprays significantly increased the Mg content in rice leaves. In soil cultures, the use of N fertilizer and Mg foliar spray did not significantly increase the leaf Mg content, except at a concentration of 12.5 g/L, indicating that the leaf Mg content may be related to the root uptake of Mg.