Acta Entomologica Sinica

Optimatization of leg regeneration of Blattella germanica (Blattaria: Blattidae) by autotomy

ZHAO Fang-Ming, LONG Xin-Yi, WEN Ye-Jie, REN Chong-Hua, LI Sheng, PENG Hong-Yuan

2023, 66(4): 439-449. doi:10.16380/j.kcxb.2023.04.001

Abstract ( 38 )

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【Aim】 The purpose of this study is to identify the autotomy sites in the German cockroach (Blattella germanica), and to explore the relationship between autotomy and leg regeneration of B. germanica, so as to provide a theoretical basis for the study of insect regeneration. 【Methods】 The healthy nymphs of B. germanica at the 3rd to 6th instars were selected and amputated separately at 11 sites of the right hindleg, including the proximal 1st segment of tarsus, proximal 2nd segment of tarsus, joint site of tarsus and tibia, one-third, one half and two-thirds from distal tibia, joint site of tibia and femur, one half of femur, joint site of femur and trochanter, joint site of trochanter and coxa, and base of coxa. The treated nymphs of B. germanica were observed daily to record whether the phenomenon of autotomy occurred. And the time and sites of autotomy, and regeneration or not after molting were also recorded. By using the length of the unamputated left hindleg as the control, the differences in the regenerated legs between autotomy and without autotomy in B. germanica were analyzed and compared, and the relationship between autotomy and leg regeneration was analyzed.【Results】Two autotomy sites were recorded in all the 11 amputation sites of B. germanica nymphs. One autotomy site was at the end of the trochanter when amputation was performed at different parts of tibia, the joint site of tibia and femur, and one half of femur, the other was at the end of tibia when amputation was performed at the 1st and 2nd segments of proximal tarsus. There was no autotomy detected in leg amputation treatments at the other sites. The autotomy sites were decided by amputation sites but not affected by nymphal instars. At different amputation sites with the same site of autotomy, there was a positive correlation between the degree of amputation and the probability of autotomy in the same nymphal instar. While there was a negative correlation between the nymphal instars and the probability of autotomy when leg amputation was performed at the same site. Autotomy did not affect whether regeneration happened or not but influenced the sites of regeneration. When autotomy occurred at the end of trochanter or at the end of tibia, a completly new leg was regenerated or tarsus was regenerated at the end of tibia. When autotomy did not happen, regeneration occurred at the amputation sites. At the same time, the length of the regenerated leg of the individuals under autotomy was significantly longer than that of the individuals without autotomy, this phenomenon was more obvious when the leg was amputated at the joint site of tibia and femur and at two-thirds from distal tibia. It was more coordinated for the proportion of regenerated legs under autotomy than that without autotomy, and the length of sensilla on regenerated legs under autotomy was much longer than that without autotomy. 【Conclusion】B. germanica can optimize the regeneration by autotomy. There are two autotomy sites at the end of trochanter and the end of tibia, respectively, and the regenerative ability is strong at these two autotomy sites. B. germanica faces a choice between autotomy and limb salvage when its leg is amputated: when limb autotomy can optimize the length and sensilla integrity of the regenerated legs, B. germanica prefers to choose autotomy, while when the regeneration can not be optimized by autotomy, no autotomy will happen.

Screening of reference genes for real-time quantitative PCR in Grapholita molesta (Lepidoptera: Tortricidae)

HAN Hui, PANG Qin-Wei, LIU Xiao-Qing, LIANG Bao-Lian, GAO Ling-Ling, MA Rui-Yan, GUO Yan-Qiong

2023, 66(4): 450-458. doi:10.16380/j.kcxb.2023.04.002

Abstract ( 26 )

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【Aim】The aim of this study is to find out the reference genes stably expressed in different developmental stages and adult tissues of Grapolita molesta and in its adults after treatment with different concentrations of three insecticides, so as to lay a foundation for the subsequent study on target gene expression in G. molesta.【Methods】Ten candidate reference genes (β-actin, 18S rRNA, β-tubulin, EF-1α, RPL13, RPL32, RSPL40, UBC7, α-tubulin and RPS20) were selected based on G. molesta transcriptome data. The expression levels of the candidate reference genes in different developmental stages (egg, 1st-5th instar larvae, pupa and adult) and different adult tissues (head, foregut, midgut, hindgut, fat body, Malpighian tubules, testis and ovary) of G. molesta and in G. molesta adults treated with three insecticides at different concentrations (avermectin: 19.819, 72.897 and 179.663 μg/mL; imidacloprid: 17.638, 163.323 and 762.986 μg/mL; and lambda-cyhalothrin: 33.791, 96.123 and 198.282 μg/mL) with the method of residual film in glass tube were detected using real-time quantitative PCR (qRT-PCR). The expression stabilities of the 10 candidate reference genes were evaluated by geNorm, NormFinder, ΔCt, BestKeeper and RefFinder. The cytochrome P450 gene CYP354A32 of G. molesta was selected for validation. 【Results】 qRT-PCR results combined with software evaluation results revealed that the expression stabilities of the reference genes in different developmental stages of G. molesta were ranked in a descending order of β-tubulin, 18S rRNA, EF-1α, RPL13, β-actin, RPS20, UBC7, RPL32, α-tubulin and RSPL40, those in different adult tissues were ranked in a descending order of UBC7, β-tubulin, β-actin, 18S rRNA, RSPL40, EF-1α, RPS20, RPL13, RPL32 and α-tubulin, and those in adults after exposure to different concentrations of avermectin, imidacloprid and lambda-cyhalothrin were ranked in a descending order of RPS20, RPL13, β-tubulin, β-actin, RPL32, RSPL40, EF-1α, UBC7, α-tubulin and 18S rRNA. The expression characteristics of CYP354A2 analyzed by using the obtained reference gene combinations showed that CYP354A2 was highly expressed in the old larvae and adults when using the combination of β-tubulin, EF-1α and 18S rRNA as the reference genes, and was highly expressed in the testis and ovary of adults when using the combination of UBC7, β-tubulin and β-actin as the reference genes. After G. molesta adults were exposed to different concentrations of insecticides, only the expression level of CYP354A2 in the treatment with 19.819 μg/mL avermectin was higher than that in the control, while the expression levels of CYP354A2 in treatments with other concentrations of insecticides were lower than that in the control when using the combination of RPS20, RPLB and β-tubulin as the refernece genes.【Conclusion】 The combination of β-tubulin, 18S rRNA and EF-1α is recommended as the reference genes for studying the target gene expression in different developmental stages of G. molesta, that of UBC7, β-tubulin and β-actin as the reference genes for studying the target gene expression in different adult tissues of G. molesta and that of RPS20, RPL13 and β-tubulin as the reference genes for studying the target gene expression in adults of G. molesta after treatment with different concentrations of avermectin, imidacloprid and lambda-cyhalothrin.

Cloning and expression profiles of fatty acid synthase gene from Trichogramma dendrolimi (Hymenoptera: Trichogrammatidae) and its functional analysis in diapause

HE Bing-Xin, ZHANG Xue, ZHANG Jun-Jie, ZHENG Mei-Xin, LI Hui

2023, 66(4): 459-468. doi:10.16380/j.kcxb.2023.04.003

Abstract ( 24 )

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【Aim】 This study aims to clone the fatty acid synthase (Fas) gene of Trichogramma dendrolimi (TdFas) and analyze its regulatory role in diapause, so as to provide a new basis for diapause research of T. dendrolimi. 【Methods】 Based on the T. dendrolimi transcriptomic data, the full-length cDNA sequence of TdFas was cloned and analyzed by bioinformatics methods. RT-qPCR was used to detect its expression level in prepupae, pupae and adults of diapause and non-diapause individuals, and in prepupae during diapause induction and maintenance period and diapause termination period. The expression of TdFas was interfered by RNAi through soaking T. dendrolimi larvae in dsTdFas solution at the concentrations of 1 000, 2 000 and 3 000 ng/μL to explore its effects on the diapause rate and relative triglyceride content of T. dendrolimi. 【Results】 The full-length cDNA sequence of TdFas (GenBank accession number: OP146440) of T. dendrolimi was cloned and is 8 601 bp in length. The open reading frame of TdFas is 7 278 bp in length, encoding a putative protein of 2 426 amino acids with a typical β-ketoyl reductase domain of fatty acid synthase. The phylogenetic analysis results showed that Td-qPCR results showed that the expression levels of TdFas in diapause prepupae and diapause adults were significantly higher than those in non-diapause individuals, while that in diapause pupae was significantly lower than that in non-diapause individuals. The expression level of TdFas in diapause prepupae increased first and then decreased with time during diapause induction and maintenance period and diapause termination period, and was the highest on the 40th day of diapause induction and maintenance, and the 40th day of diapause termination, respectively. RNAi results showed that 3 000 ng/μL dsTdFas was optimal for silencing TdFas, and in the treatment with this concentration of dsTdFas, the diapause rate of T. dendrolimi (66.04%) was significantly lower than those in the blank control group (96.67%) and dsGfp negative control group (93.88%), and the relative triglyceride content in prepupae was also significantly reduced as compared to those in the two control groups. 【Conclusion】 TdFas of T. dendrolimi has been identified for the first time in this study, and may play an important role in diapause regulation of T. dendrolimi. This study provides a theoretical basis for further study of the mechanism of diapause regulation of T. dendrolimi.

Bioinformatic analysis and functional study on chitin synthase gene in Apis mellifera

GUO Yi-Long, ZHAO Xiao, ZHANG Tian-Ze, SONG Yu-Xuan, ZHAO Hao-Dong, FAN Xiao-Xue, REN Zhong-Min, ZHANG Jie, ZHAO Hong-Xia, XU Xi-Jian, CHEN Da-Fu, GUO Rui

2023, 66(4): 469-477. doi:10.16380/j.kcxb.2023.04.004

Abstract ( 30 )

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【Aim】 This study aims to elucidate the molecular characters of chitin synthase (CHS) gene in Apis mellifera and uncover the function of CHS in immune response of A. mellifera worker larvae to Ascosphaera apis stress. 【Methods】 The molecular characters,
conserved motifs and structural domains of the A. mellifera CHS protein were predicted and analyzed using relevant bioinformatics software. Phylogenetic analysis of amino acid sequences of CHS proteins in A. mellifera and other insects was performed with MEGA X software. The dsRNAs of CHS and egfp were synthesized via in vitro transcription method, and fed to the A. apis-stressed 3-day-old larvae of A. mellifera workers to perform RNAi. RT-qPCR was used to determine the expression levels of CHS and immune-related genes abaecin, apidaecin, birc5, defensin-1 and PGRP-S2 in the 5-day-old larval gut of A. mellifera workers in response to A. apis stress. 【Results】 The CHS protein of A. mellifera contains 1 572 amino acids belonging to 20 types of amino acids, among which the numbers of amino acids with positive and negative charge are 177 and 169, respectively. CHS has the molecular weight of 178.77 kD, isoelectric point of 6.65 and cellulose synthase CESA3 catalytic structural domain. Three motifs (Motif 1, Motif 2 and Motif 3) and two structural domains (Chitin_synth_2 and Glyco_trans_2_3) were identified in CHSs in 13 insect species such as A. mellifera and A. cerana. Phylogenetic tree showed that the CHSs in A. mellifera and A. cerana of Hymenoptera showed the highest amino acid sequence identities, and clustered into one branch with the bootstrap value of 100. The expression level of CHS in the 5-day-old larval gut of A. mellifera in the dsCHS-fed group was significantly down-regulated as compared to that in the dsegfp-fed control group, with the interference efficiency of 29.40%. In the dsCHS-fed group, the expression levels of abaecin, birc5 and defensin-1 in the 5-day-old larval gut of A. mellifera were extremely significantly up-regulated, that of PGRP-S2 was significantly up-regulated, while that of apidaecin was extremely significantly down-regulated, as compared with those in the dsegfp-fed control groups. 【Conclusion】 A. mellifera CHS may be an intracellular hydrophilic transmembrane protein. The amino acid sequences of CHSs in A. mellifera and other insects are highly conservative, and those in A. mellifera and A. cerana are the most highly conservative. CHS affects A. mellifera worker larval immune response to A. apis stress.

Identification and verification of genes and full-length transcripts of serine/threonine protein kinase in Apis mellifera ligustica

FAN Xiao-Xue, ZHANG Kai-Yao, ZHU Le-Ran, WANG Zi-Xin, ZHANG Kui-Hao, NIU Qing-Sheng, XU Xi-Jian, LUO Qun, CHEN Da-Fu, GUO Rui

2023, 66(4): 478-485. doi:10.16380/j.kcxb.2023.04.005

Abstract ( 27 )

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【Aim】To identify and analyze the genes and full-length transcripts of serine/threonine protein kinase of Apis mellifera ligustica using previously gained high-quality long-read nanopore sequencing data, and to provide reference information and bases for further functional study.【Methods】Based on the previously obtained high-quality long-read nanopore sequencing data of A. m. ligustica, the genes and full-length transcripts of serine/threonine protein kinase were screened from the Nr database by Blast. The screened full-length transcripts of serine/threonine protein kinase were compared with the annotated transcripts in the reference genome of A. mellifera (Amel_HAv3.1) using gffcompare software to identify the unannotated new genes and new transcripts. The types of alternative splicing (AS) events occurring in serine/threonine protein kinase genes were identified using Astalavista software. Visualization of the structure of spliceosomes was performed with IGV browser. RT-PCR was employed to confirm the authenticity of randomly selected six AS events.【Results】In total, 71 genes and 335 full-length transcripts of serine/threonine protein kinase of A. m. ligustica were identified, and one new gene and 97 new transcripts were discovered. The structure of 14 annotated genes was optimized, and the 5′ends of six genes and the 3′ends of eight genes were prolonged, respectively. A total of 57 AS events were identified in seven genes of serine/threonine protein kinase in A. m. ligustica, including 40 exon skipping (ES) events, 15 alternative 5′splicing site (A5SS) events and two alternative 3′splicing site (A3SS) events. RT-PCR results of randomly selected six AS events indicated that all of the target fragments were in accordance with the expected sizes, confirming the authenticity of AS events.【Conclusion】 Genes and full-length transcripts of serine/threonine protein kinase of A. m. ligustica were systematically identified and the structure of the serine/threonine protein kinase genes annotated in A. mellifera reference genome was optimized in this study.

Identification of Lecanicillium araneicola HK-1 and its biocontrol potential against Aphis craccivora (Hemiptera: Aphididae)

LIU Sheng-Ke, CHEN Cong-Ling, SHEN Yu-Ying, LI Jin-Hua, TAN Zhi-Qiong, JIN Peng-Fei

2023, 66(4): 486-500. doi:10.16380/j.kcxb.2023.04.006

Abstract ( 16 )

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【Aim】Aphids are one of the most destructive pests in agricultural production, causing huge agricultural economic losses every year. In this study, a fungus strain HK-1 isolated from dead aphids was identified, its biological characters were analyzed, and the virulence of its conidia to Aphis craccivora adults and its sensitivity to chemical pesticides were determined, in order to provide a theoretical basis for the large scale production and application of Lecanicillium.【Methods】The HK-1 strain was identified by combining morphological charactersistics with multi-gene analysis. The mycelial growth rate, spore production and spore germination rate of the strain HK-1 were determined by changing the medium, pH, carbon and nitrogen sources, respectively. The lethality and the median lethal time (LT₅₀) of the spore suspension against A. craccivora adults were measured by immersion method. The growth rate method was used to determine the median effective concentration (EC₅₀) of common pesticides against this strain.【Results】The strain HK-1 was identified as Lecanicillium araneicola HK-1. The results of biological characters revealed that L. araneicola HK-1 had better growth, spore production and spore germination on potato dextrose agar (PDA) medium than on other media. L. araneicola HK-1 grew fastest at pH 9.0, and had the most spore production at pH 6.0 and 7.0 and the best sopre germination at pH 6.0. In terms of carbon source utilization, the optimal carbon source of L. araneicola HK-1 was sucrose for growth, sorbitol and maltose for spore production, and mannitol and glucose for spore germination. In terms of nitrogen source utilization, the best nitrogen source for growth and spore germination of L. araneicola HK-1 was beef extract and that for spore production was ammonium chloride. Laboratory virulence assay showed that the cumulative mortality rate of A. craccivora adults caused by 1×10⁸ conidia/mL of L. araneicola HK-1 suspension in 6 d was 61.67%. The LT₅₀ value of L. araneicola HK-1 against A. craccivora adults was 3.35 d, and decreased with the increase of the tested conidial concentration. The EC₅₀ values of 5% acetamiprid EC, 10% nitenpyram EC and 6% kasugamycin WP against L. araneicola HK-1 were 32.01, 3 250.46 and 164.02 μg/mL, respectively. 【Conclusion】 L. araneicola HK-1 isolated from this study has a good biocontrol potential against A. craccivora adults.

Expression of attacin gene LsAttacin2 of Lasioderma serricorne (Coleoptera: Anobiidae) and its role in antibacterial stress

XIA Peng-Liang, YAN Yi, SONG Xing-Yi, HUANG Yong, YANG Wen-Jia

2023, 66(4): 501-509. doi:10.16380/j.kcxb.2023.04.007

Abstract ( 20 )

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【Aim】 This study aims to clarify the function of an attacin gene (LsAttacin2) in Lasioderma serricorne larvae in response to bacterial infection.【Methods】The full-length cDNA sequence of LsAttacin2 from L. serricorne was amplified by RT-PCR. The relative expression levels of LsAttacin2 in different developmental stages (egg, early larva, late larva, pupa, callow adult and mature adult) and various tissues (head, cuticle, foregut, midgut, hindgut, fat body and Malpighian tubules) of the 4th instar larvae of L. serricorne, and in the 4th instar larvae after infection with Escherichia coli and Staphylococcus aureus and treatments with their peptidoglycans were examined by RT-qPCR. After silencing the expression of LsAttacin2 by RNAi through injection, the mortalities of the 4th instar larvae of L. serricorne post infection with E. coli and S. aureus were detected.【Results】The full-length cDNA sequence of LsAttacin2 (GenBank accession number: MT635176) in L. serricorne was obtained. The open reading frame of LsAttacin2 is 504 bp in length encoding 167 amino acid residues. LsAttacin2 has a signal peptide at the N-terminus and a conserved domain of Attacin_C superfamily at the C-terminus. The RT-qPCR results showed that LsAttacin2 was expressed in the tested various developmental stages and highly expressed in the late larva and pupa. LsAttacin2 was mainly expressed in immune tissues, such as midgut, cuticle and fat body of the 4th instar larva. Both E. coli and S. aureus and their peptidoglycan induced the up-regulated expression of LsAttacin2 in the 4th instar larvae of L. serricorne. RNAi combined with bacterial bioassay results showed that the expression levels of LsAttacin2 in the 4th instar larvae in the dsLsAttacin2 injection groups were significantly reduced by 72.8% and 80.4% at 24 and 48 h, respectively, as compared to those in the control groups (injected with dsGFP). The mortalities of the 4th instar larvae at 24 h after infection with E. coli and S. aureus in the dsLsAttacin2 injection groups at 48 h after RNAi increased by 21.1% and 24.4%, respectively, as compared to those in the control groups injected with dsGFP.【Conclusion】The results of this study suggest that LsAttacin2 plays an important role in the immune response of L. serricorne against the bacterial infections.

Effects of single and combined seed soaking treatments with CaCl₂and SA on rice resistance to Nilaparvata lugens (Hemiptera: Delphacidae)

DENG Qian-Qian, YE Mao, WU Xiao-Bao, ZHU Zhong-Yan, CHEN Li-Na, XIE Jing

2023, 66(4): 510-521. doi:10.16380/j.kcxb.2023.04.008

Abstract ( 24 )

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【Aim】To explore the effects of single and combined seed soaking treatments with calcium chloride (CaCl₂) and salicylic acid (SA) on rice resistance to the brown planthopper (BPH), Nilaparvata lugens.【Methods】Rice seeds were soaked in 20 mmol/L CaCl₂ solution (CaCl₂), 1 mmol/L SA solution (SA) or a solution combined with them (SA+CaCl₂) for 48 h, meanwhile the control seeds were soaked in distilled water. During the tillering stage, the expression levels of defense genes including transcription factor genes OsWRKY70 and OsWRKY53, OsNPR1 (one of key regulators of SA signaling pathway) and OsPAL1 (a key gene involved in SA synthesis), and the activities of defense enzymes induding phenylalanine ammonia lyase (PAL), peroxidase (POD), polyphenol oxidase (PPO) and β-1, 3-glucanase (β-1,3-GA) in leaf sheaths of rice plants subjected to different seed soaking treatments, under the infestation of the 3rd instar nymphs of N. lugens were tested, and the survival rates and developmental duration of N. lugens fed on rice plants subjected to various seed soaking treatments were detected as well. 【Results】Without infestation of N. lugens, the expression levels of OsWRKY53, OsNPR1 and OsPAL1 in leaf sheaths of rice plants subjected to single and combined seed soaking treatments with CaCl₂ and SA showed no significant difference. The expression levels of OsWRKY53, OsNPR1 and OsPAL1 in leaf sheaths of the control rice plants were significantly increased at 180 min after infestation by the 3rd instar nymphs of N. lugens as compared to those in leaf sheaths of the control rice plants uninfested by N. lugens. OsNPR1 and OsPAL1 in leaf sheaths of rice plants subjected to seed soaking treatment with CaCl₂ reached the highest expression levels at 90 and 120 min after infestation of N. lugens, respectively, which were significantly higher than those in leaf sheaths of the control rice plants at the corresponding infestation time points. OsWRKY70 exhibited higher expression level in leaf sheaths of rice plants subjected to seed soaking treatment with CaCl₂ than in leaf sheaths of rice plants subjected to seed soaking treatments with SA and SA+CaCl₂ at each infestation time. The expression levels of OsWRKY53 and OsPAL1 in leaf sheaths of rice plants subjected to seed soaking treatment with SA were significantly higher than those subjected to the other seed soaking treatments at 180 and 90 min after infestation of N. lugens, respectively. The expression levels of OsWRKY53 in leaf sheaths of rice plants subjected to seed soaking treatment with SA+CaCl₂ at 90 and 120 min after infestation of N. lugens, and those of OsNPR1 in leaf sheaths of rice plants subjected to seed soaking treatment with SA+CaCl₂ at 60 and 180 min after infestation of N. lugens were significantly higher than those subjected to the other seed soaking treatments at the corresponding infestation time, while the expression levels of OsPAL1 in leaf sheaths of rice plants subjected to seed soaking treatment with SA+CaCl₂ were significantly lower than those subjected to the other seed soaking treatments at all the tested infestation time points. The activities of PAL and β-1,3-GA in leaf sheaths of rice plants subjected to seed soaking treatment with CaCl₂, those of PAL, POD, PPO and β-1,3-GA in leaf sheaths of rice plants subjected to seed soaking treatments with SA and SA+CaCl₂ were significantly higher than those in leaf sheaths of the control rice plants. The activities of all the four defense enzymes in leaf sheaths of the control rice plants infested by N. lugens increased as compared to those in leaf sheaths of the control rice plants uninfested by N. lugens, and the ascending degrees of PAL, POD and PPO activities in leaf sheaths of rice plants subjected to single and combined seed soaking treatments with CaCl₂ and SA were higher than those in leaf sheaths of the control rice plants. Seed soaking treatment with SA+CaCl₂ had obvious induction effect on the POD activity under infestation of N. lugens. The survival rates of N. lugens nymphs fed on rice plants subjected to seed soaking treatments with CaCl₂, SA and SA+CaCl₂ were 9.03%, 13.82% and 19.61%, respectively, lower than that fed on the control rice plants at 8 d after infestation, and the nymphal duration of N. lugens fed on the rice plants subjected to seed soaking treatments with CaCl₂, SA and SA+CaCl₂ was significantly prolonged as compared to that fed on the control rice plants. The N. lugens nymphs fed on the rice plants subjected to seed soaking treatment with SA+CaCl₂ displayed the lowest survival rate. 【Conclusion】Single and combined seed soaking treatments with CaCl₂ and SA have different induction effects on the expression levels of OsWRKY70, OsWRKY53, OsNPR1 and OsPAL1 and the activities of defense enzymes PAL, POD, PPO and β-1,3-GA, while the combined seed soaking treatment with CaCl₂ and SA has a synergistic effect on rice resistance to N. lugens.

Seasonal and latitudinal variations of life history traits in Monochamus alternatus (Coleoptera: Cerambycidae) in Jiangxi Province, Southeast China

PAN You-Liang, LUO Zhi-Di, LI Hong-Zheng, LI Jin, GUAN Zhong-Min, JIAO Ting, LIU Xing-Ping

2023, 66(4): 522-530. doi:10.16380/j.kcxb.2023.04.009

Abstract ( 24 )

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【Aim】To explore the effects of oviposition season and geographical latitude on life history traits of the Japanese pine sawyer beetle, Monochamus alternatus, so as to provide a basis for the accurate prediction and management of this insect pest.【Methods】Six monitoring plots along the latitudinal gradient of about 1° in Jiangxi Province, Southeast China were established, then the generation differentiation and developmental duration were investigated by field pine tree trunk covering observation, and the overwintering larval instars were surveyed through dead wood dissecting.【Results】The 2nd generation differentiation of M. alternatus occurred in southern and central Jiangxi. The proportion of the differentiation entering the 2nd generation decreased from 45.75% to 2.46% in southern Jiangxi and from 17.42% to 0 in central Jiangxi with the delay of oviposition season, while there was only one generation in northern Jiangxi, where no generation differentiation occurred. The proportion of the eggs laid at the same month entering the 2nd generation decreased from 21.92% to 0 with increasing geographical latitude. The egg-pupal duration in differentiated and undifferentiated individuals in the forest was 110.66-122.01 and 330.61-366.01 d, respectively, and showed a latitudinal co-gradient variation and a counter-gradient variation, respectively. However, no significant difference was found in the developmental duration of differentiated and undifferentiated individuals. The overwintering larvae were at the 2nd-5th instars in southern and central Jiangxi and 4th-5th instars in northern Jiangxi, and the proportion of the 2nd instar overwintening larvae significantly decreased from 12.47% to 0 and the proportion of the 5th instar overwintering larvae significantly increased from 45.33% to 98.40% with increasing geographical latitude.【Conclusion】Oviposition season and geographical latitude have certain effects on the life history traits of M. alternatus, showing that oviposition season and geographical latitude significantly affect the generation differentiation proportion of this beetle, but not on the developmental duration of differentiated individuals and undifferentiated individuals. The larval instars and proportion of overwintering insects are obviously affected by geographical latitude.

Evaluation of feeding capacity and growth and development of Tuta absoluta (Lepidoptera: Gelechiidae) based on functional responses and two-sex life table

ZHOU Jun-Hui, LUO Wen-Fang, HE Wei, SUN Xiao-Jun, ZHONG Wei-Juan, XU Jian-Jun

2023, 66(4): 531-537. doi:10.16380/j.kcxb.2023.04.010

Abstract ( 18 )

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【Aim】 The tomato leaf miner, Tuta absoluta, is a destructive pest on solanaceous crops. This study aims to clarify the feeding capacity, intraspecific competition and growth and development of T. absoluta, so as to provide a theoretical basis for the effective control of T. absoluta. 【Methods】 The feeding capacity (food consumption), intraspecific competition (intensity of scramble competition), growth, development and reproductive parameters (developmental duration, adult longevity, female to male sex ratio, number of eggs laid per female and survival rate) and population parameters (intrinsic rate of increase, finite rate of increase, net reproductive rate and mean generation time) of T. absoluta were determined under laboratory conditions based on functional response equation, intraspecific interference model and two-sex life table. 【Results】 The functional responses of the 3rd and 4th instar larvae of T. absoluta fed on tomato leaves fitted to the Holling Ⅱ model, and their searching efficiencies to tomato leaves were 0.448 and 0.363, their handling time to tomato leaves was 0.016 and 0.008 d, and the daily maximum food consumption was 55.56 and 166.67 mg, respectively. Under the conditions of the given amount of diet, there was strong intraspecific competition between the 3rd and 4th instar larvae of T. absoluta, and the intensity of scramble competition of the 3rd instar larva was stronger than that of the 4th instar larva. The population parameters of T. absoluta analyzed by the two-sex life table showed that the intrinsic rate of increase, finite rate of increase, net reproductive rate and mean generation time of T. absoluta fed on tomato leaves were 0.09 d-1, 1.09 d-1, 19.80 and 32.92 d, respectively. 【Conclusion】 The 4th instar larva of T. absoluta has strong feeding capacity, and its generational reproduction speed is fast, causing serious harm to tomato crops. The research on the feeding capacity and growth and development of T. absoluta larva has important guiding significance for its control.

Comparative studies on the structure and response of compound eyes in adults of diurnal moth Phauda flammans (Lepidoptera: Phaudidae) and nocturnal moth Spodoptera litura (Lepidoptera: Noctuidae) to light and dark conditions

HUANG Ji-Shan, WU Hai-Pan, WANG Xiao-Yun, LU Wen, ZHENG Xia-Lin

2023, 66(4): 538-552. doi:10.16380/j.kcxb.2023.04.011

Abstract ( 10 )

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【Aim】This study aims to compare the difference in the external morphology and internal microstructure of compound eyes and the changes of ommatidial structure and pigment granules between a diurnal moth Phauda flammans and a nocturnal moth Spodoptera litura under natural light and completely dark conditions, so as to lay a foundation for further exploring the survival and reproductive mechanisms of diurnal and nocturnal moths based on vision.【Methods】The external morphology of the compound eyes of P. flammans and S. litura adults was observed, and the parameters such as the number of ommatidia and length of compound eyes were measured by using scanning electron microscopy. The internal tissue structure of the compound eyes of adults were observed using paraffin sectioning technology. The light- and dark-adapted states of compound eyes of adults under natural light and completely dark conditions were observed using digital microscope. 【Results】The length ［(1.67±0.05) mm］ and width［(1.57±0.02) mm］ of compound eyes and number of ommatidia (8 816.38±25.56) of S. litura adults were significantly greater than those of P. flammans adults［(0.74±0.11) mm, (0.66±0.01) mm and 820.55, respectively］. Under natural light and completely dark conditions, the compound eyes of S. litura adults underwent a significant transition in light- and dark-adapted states, while no obvious changes of compound eyes of P. flammans adults were observed. Under natural light condition, the pigment granules of P. flammans were evenly distributed on both sides of the rhabdom and crystalline cone, while the pigment granules of S. litura were distributed between the crystalline cone and the clear zone. Under completely dark condition, the pigment granules in the retinula cells of both species moved to the distal region of the ommatidia, and the pigment granules on both sides of the crystalline cone increased. Under completely dark condition, the length of crystalline cone, rhabdom and retinula cell nucleus of P. flammans significantly reduced, while the distance from retinula cell nucleus to basement membrane of P. flammans significantly increased, the width of rhabdom of S. litura increased significantly, but the other ommatidial structure of S. litura showed no significant changes, as compared with those under natural light condition. Under natural light condition, the length of ommatidia, length of crystalline cone and distance from the retinula cell nucleus to basement membrane of P. flammans were significantly smaller than those of S. litura, while the corneal thickness, length of rhabdom, and length and width of retinula cell nucleus of P. flammans were significantly larger than those of S. litura. Under completely dark condition, the length of ommatidia, length of crystalline cone and distance from retinula cell nucleus to basement membrane of P. flammans were significantly smaller than those of S. litura, while the corneal thickness, length of rhabdom, width of crystalline cone and length and width of retinula cell nucleus of P. flammans were significantly larger than those of S. litura.【Conclusion】The compound eyes of P. flammans and S. litura adults are apposition eyes and superposition eyes, respectively. Although the moving direction of pigment granules in the ommatidia of P. flammans is the same as that in S. litura under different light and dark conditions, the changes of adaptational states of compound eye, crystalline cone and rhabdom structure in the ommatidium of the two moths are different, which may be related to their different photosensitive mechanisms.

Effects of Cu²⁺and avermectin and their combined stress on the growth and development and reproductive behavior of Ostrinia furnacalis (Lepidoptera: Pyralidae)

GUO Xin, XU Fan-Shu, WEI Hong-Yi, CHEN Li-Hui

2023, 66(4): 553-563. doi:10.16380/j.kcxb.2023.04.012

Abstract ( 18 )

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【Aim】 To explore the effects of the heavy metal Cu²⁺ and the pesticide avermectin and their combined stress on the growth and development and reproductive behavior of the Asian corn borer, Ostrinia furnacalis in farmland.【Methods】 We added 50 mg/kg of Cu²⁺ and 0.039 mg/L of avermectin (LC₁₀concentration against the 3rd instar larvae of O. furnacalis) to the artificial diet, respectively, and simultaneously, and then got three kinds of treated diets containing Cu²⁺ (Cu), avermectin (Av) and both (Av+Cu),
taking the normal artificial diet as the blank control group. We fed the neonate larvae of O. furnacalis with the four diets under laboratory conditions, and systematically investigated and recorded the parameters of growth and development (larval duration, pupal
duration, pupal weight, adult weight, growth rate, adult emergence rate and adult longevity)， calling behavior (calling rate and average calling duration), orientation behavior (take-off rate, orientation rate, average response time, flying halfway rate and landing to pheromone source rate), and reproduction (number of eggs laid per female and egg hatching rate).【Results】 Cu, Av and their combined stress (Av+Cu) had certain effects on the growth and development and reproduction of O. furnacalis. On the one hand, the postembryonic developmental duration (larval plus pupal duration) of female and male O. furnacalis in Cu treatment alone was significantly shortened as compared to that in the blank control group. After Av treatment alone, the postembryonic developmental duration of female and male O. furnacalis was significantly prolonged to 38.31 and 38.95 d, respectively, being 67.07% and 67.38% longer than that of the blank control group, respectively. After Cu treatment alone, the body weight of female pupae, male pupae, female adults and male adults of O. furnacalis decreased significantly, being 13.16%, 6.45%, 7.13% and 4.60% lower than that of the blank control group, respectively. Then after Av treatment alone, the body weight of female pupae, male pupae and female adults of O. furnacalis decreased significantly, being 26.50%, 8.96% and 12.46% lower than that of the blank control group, respectively, while the body weight of male adults was significantly higher than that of the blank control group by 6.05%. At the same time, Cu treatment had a certain impact on the calling behavior of female adults. After Cu treatment, the highest calling rate and average calling duration in each scotophase decreased with the scotophase, while those in the blank control group showed a trend of increasing first and then decreasing with the scotophase. After Av treatment, the calling behavior of female adults was promoted: the highest calling rates in all scotophases except the scotophase 5 (the 5th scotophase after emergence of females) reached 100%; the average calling duration in Av treatment groups was significantly longer than that in the blank control groups in all scotophases except the scotophase 3 (the 3rd scotophase after emergence of females), and the average calling duration in Av treatment group was the highest (5.71 h) in scotophase 5. Compared to the blank control group, Cu and Av treatment alone significantly inhibited the orientation behavior of male adults and the number of eggs laid per female of O. furnacalis. On the other hand, the effects of the combined stress of Av and Cu and their single stresses were different. Compared to the blank control group, Av+Cu treatment inhibited the growth and development of O. furnacalis, causing significant extension of the developmental duration and body weight loss. The female and female postembryonic developmental duration in Av+Cu treatment was 37.60 and 37.04 d, respectively, only shorter than that in Av treatment. The body weight of female and male pupae and female adults in the Av+Cu treatment group was the lowest, significantly lower than that in the blank control group. In the mating combinations of female and male adults stressed by Av+Cu and female and male adults in the blank control group, the landing to pheromone source rate of male adults and the number of eggs laid per female were significantly lower than those of the mating combination of female and male adults in the blank control group, and both were the lowest. The calling behavior of female adults of O. furnacalis after Av+Cu stress was relatively consistent with that after Av treatment, and the highest calling rates in all scotophases reached 100%. The average calling duration in each scotophase in Av+Cu treatment group was significantly longer than that in the blank control group and Cu treatment group, and showed no significant difference from that in Av treatment group, and the average calling duration in Av+Cu treatment was the longest (6.16 h) in scotophase 3.【Conclusion】Single and combined stresses of Cu and Av inhibit the growth and development, disturb the reproductive behavior of adults and reduce the fecundity of O. furnacalis. Among the effects of the combined stress of Cu and Av on O.furnacalis, Av plays a leading role.

Study of mate selection and fecundity of Spodoptera frugiperda(Lepidoptera: Noctuidae)

WU Ting, ZHANG Qiu-Lang, ZHAO Qing-Yi, XU Jin, YE Hui

2023, 66(4): 564-574. doi:10.16380/j.kcxb.2023.04.013

Abstract ( 24 )

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【Aim】To explore the main mate selection strategies and their relationship with the fecundity in the fall armyworm, Spodoptera frugiperda, and to explore the evolutionary significance and mechanism of mate selection strategies based on the theory of sexual selection.【Methods】Marked female and male adults of S. frugiperda with different day-old ages, body weight and mating experiences were paired, and their mate selections were observed, the morphological characteristics (body length, antennal length, wing length, and thoracic and abdominal length and width) and fecundity (number of eggs laid per female, egg hatching rate and number of hatched larvae) of mated and unmated female and male adults were measured and compared. 【Results】Both female and male adults of S. frugiperda preferred to mate with young, heavy and unmated adults. The probability of female adults selecting young (3-day-old) male adults to mate (65.45%) was significantly higher than that selecting old (7-day-old) male adults to mate (34.55%), and the probability of male adults selecting 3-day-old female adults to mate (82.35%) was significantly higher than that selecting 7-day-old female adults to mate(17.65%). The probability of female adults selecting heavy male adults to mate (74.58%) was significantly higher than that selecting light males to mate (25.42%), and the probability of male adults selecting heavy female adults to mate (66.67%) was significantly higher than that selecting light females to mate (33.33%). The probability of female adults selecting male adults without mating experience to mate (64.91%) was significantly higher than that selecting males with mating experience to mate (35.09%), and the probability of male adults selecting female adults without mating experience to mate (78.57%) was significantly higher than that selecting females with mating experience to mate (21.43%). The body length, antennal length and wing length of male adults who obtained mating rights were significantly greater than those of males who did not obtain mating rights, while the body length, wing length, and abdominal length and width of female adults who obtained mating rights were significantly greater than those of females who did not obtain mating rights. Fecundity studies showed that compared to the female adults who chose to mate with male adults with mating experience, female adults who chose to mate with male adults without mating experience could achieve higher number of eggs laid per female (unmated vs mated: 1 024 grains vs 917 grains) and egg hatching rate (unmated vs mated: 91.36% vs 89.10%). Compared to old and light female adults chosen by male adults to mate, young and heavy female adults chosen by male adults to mate had higher number of eggs laid per female (young vs old: 1 001 grains vs 939 grains; heavy vs: light: 1 039 grains vs 830 grains) and number of hatched larvae (young vs old: 917 vs 838; heavy vs light: 950 vs 754). The age and body weight of male adults had no significant effects on the fecundity of female adults. 【Conclusion】 Both female and male adults of S. frugiperda have mate selection preferences related to morphological and physiological traits. Female and male adults can obtain material benefits (more offspring) to different degrees through mate selection, thus contributing to the reproduction and evolution of the species. This study contributes to the study of insect reproductive behavior and sexual selection mechanism, and to the exploration of pest control strategies based on reproductive behavior.

Research advances on the mutual defense between host plants and piercing-sucking insects

ZHANG Jing, DUAN Zhi-Rou, LIU Chang-Quan, PENG Ying-Chuan, ZHANG Wan-Na, XIAO Hai-Jun

2023, 66(4): 575-590. doi:10.16380/j.kcxb.2023.04.014

Abstract ( 13 )

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Host plants and insects have formed complex defense and counter defense mechanisms in the long-term co-evolution. In this article, we systematically reviewed the process and mechanism of the mutual defense in host plant-piercing-sucking insect interactions. The piercing-sucking insects use specialized needles to suck the sap of the host plant tissue. Plants sense insect feeding signals through cell membrane surface or intracellular receptors, and activate plant immunity through signal transduction pathways such as mitogen-activated protein kinase (MAPK) signaling pathway, plant hormone signaling pathway, calcium ion signaling pathway, transcription factor regulation, Rop/Rac GTPase signaling pathway and reactive oxygen species (ROS) pathway. To prevent further insect feeding, host plants form a strengthened physical barrier and induce the production of secondary metabolites, anti-nutritional enzymes, anti-digestive enzymes and callose deposition, and release volatiles and other defense mechanisms. In the process of “gaming” with host plants, piercing-sucking insects often use secreted salivary components during the feeding to target plant proteins. By destroying the physical barrier of host plants, or inhibiting the resistance signal transduction of host plants, or inhibiting the toxic effect of the host secondary metabolites, or by means of cross-border RNA and horizontal gene transfer, piercing-sucking insects inhibit the plant defense response and continue feeding to cause damage. In addition, based on the plant-pathogen interaction model, and combined with the research advance of the host plant-piercing-sucking insect interaction, we summarized the development of the interaction model between host plants and piercing-sucking insects. Since the host plant-insect interaction is sophisticated, a profound study on the mutual defense processes and molecular mechanisms of the host plant-piercing-sucking insect interaction will not only help deepen the understanding of their co-evolution, but also help to provide theoretical foundation and references for developing new approaches and technologies for crop insect pest control.

Research progress on host location of parasitoids based on olfactory signal recognition and its mechanism

LIN Ya-Ping, HOU You-Ming

2023, 66(4): 591-608. doi:10.16380/j.kcxb.2023.04.015

Abstract ( 15 )

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Successfully locating a host is one of the crucial steps in parasitoid reproduction, which is regulated mainly by volatile compounds. Firstly, female parasitoids often use volatiles from host plants, especially herbivore-induced plant volatiles (HIPVs), to locate the habitat of their hosts at long distances, which helps female parasitoids narrow their host searching range according to the cues provided by HIPVs. The blends of HIPVs are extremely complicated, and their components and contents can be modulated by a wide range of factors. Nevertheless, terpenoids are common compounds in HIPVs and have been confirmed by most behavioral studies to play a role in host localization of parasitoids. Subsequently, when the parasitoids find a plant related to hosts and land on them, they exploit host-derived cues at a close range to locate hosts. Parasitoids are usually attracted to volatile compounds released from the host body, cocoon, feces, etc. The odor of some host feces can be used as the main cues for parasitoids to locate hosts. Moreover, the components of volatiles in host feces may vary among plant species which insects feed. In addition, semiochemicals from the parasitoid itself are also beneficial for other individuals of the same species to locate their hosts. Sensory perception of odor molecules by parasitoids relies on olfactory sensilla, primarily located on the antennae, but the research on the molecular mechanism of their olfactory recognition is still limited. Because odorant-binding proteins (OBPs) are the crucial proteins in the olfactory system that mediate odor recognition, most studies only focus on the analysis of antennal OBPs. According to the current research, the number of genes encoding OBPs is highly variable among parasitiod species, and most studies have verified that OBPs play an important role in host location of parasitoids by means of gene silencing, fluorescence competitive binding assay, molecular docking and so on. Research on host localization and olfactory mechanism of parasitoids has important ecological significance, and also has a good application perspective in the integrated management of agricultural insect pests. Applying volatile compounds, or growing companion plants and transgenic plants that emit useful volatiles can enhance the host location of parasitoids in the field, so as to achieve a better biological control efficacy against insect pests.

Contents of Vol. 66 Issue 4

2023, 66(4): 609-609.

Abstract ( 3 )

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