DNA barcoding of five common stored-product pest species of genus Cryptolestes (Coleoptera: Laemophloeidae)

Biology, Ecology, and Behavior of Rusty Grain Beetle (Cryptolestes ferrugineus (Stephens))

Cryptolestes ferrugineus, the rusty grain beetle, is a cosmopolitan pest that has adapted to cool and warm climates due to its unique biology, ecology, and behavior. The rusty grain beetle is a pest of high economic importance; hence, understanding their biology, ecology, and behavior could be useful in designing effective management strategies. An extensive literature survey was conducted using the databases Web of Science and Scopus. Information on country-wise publications from 1949 to 2023 on C. ferrugineus was provided, and a table illustrating the distribution of C. ferrugineus was also presented to demonstrate the global significance of C. ferrugineus. We overviewed their life stages, morphology, and factors influencing their biology, ecology, and behavior, such as refuge-seeking behavior, flight activity, mating behavior, interspecific interaction with other species, movement, and distribution. Mathematical models focusing on C. ferrugineus population dynamics and movement were also presented. In order to advance our knowledge on C. ferrugineus, the following possible avenues for future research were outlined: application of molecular markers and population genetic approaches to understand their evolutionary history; mechanisms responsible for adaptation and resistance to insecticide; interspecific interaction in storage facilities and wider landscapes; and identification of microbial roles in the ecology, behavior, and control of C. ferrugineus.

Mitochondrial DNA genomes of five major Helicoverpa pest species from the Old and New Worlds (Lepidoptera: Noctuidae)

Five species of noctuid moths, Helicoverpa armigera, H. punctigera, H. assulta, H. zea, and H. gelotopoeon, are major agricultural pests inhabiting various and often overlapping global distributions. Visual identification of these species requires a great deal of expertise and misidentification can have repercussions for pest management and agricultural biosecurity. Here, we report on the complete mitochondrial genomes of H. assulta assulta and H. assulta afra, H. gelotopoeon, H. punctigera, H. zea, and H. armigera armigera and H. armigera conferta' assembled from high-throughput sequencing data. This study significantly increases the mitogenome resources for these five agricultural pests with sequences assembled from across different continents, including an H. armigera individual collected from an invasive population in Brazil. We infer the phylogenetic relationships of these five Helicoverpa species based on the 13 mitochondrial DNA protein-coding genes (PCG's) and show that two publicly available mitogenomes of H. assulta (KP015198 and KR149448) have been misidentified or incorrectly assembled. We further consolidate existing PCR-RFLP methods to cover all five Helicoverpa pest species, providing an updated method that will contribute to species differentiation and to future monitoring efforts of Helicoverpa pest species across different continents. We discuss the value of Helicoverpa mitogenomes to assist with species identification in view of the context of the rapid spread of H. armigera in the New World. With this work, we provide the molecular resources necessary for future studies of the evolutionary history and ecology of these species.

Random Mating Between Two Widely Divergent Mitochondrial Lineages of Cryptolestes ferrugineus (Coleoptera: Laemophloeidae): A Test of Species Limits in a Phosphine-Resistant Stored Product Pest

Effective pest management relies on accurate delimitation of species and, beyond this, on accurate species identification. Mitochondrial COI sequences are useful for providing initial indications in delimiting species but, despite acknowledged limitations in the method, many studies involving COI sequences and species problems remain unresolved. Here we illustrate how such impasses can be resolved with microsatellite and nuclear sequence data, to assess more directly the amount of gene flow between divergent lineages. We use a population genetics approach to test for random mating between two 8 ± 2% divergent COI lineages of the rusty grain beetle, Cryptolestes ferrugineus (Stephens). This species has become strongly resistant to phosphine, a fumigant used worldwide for disinfesting grain. The possibility of cryptic species would have significant consequences for resistance management, especially if resistance was confined to one mitochondrial lineage. We find no evidence of restricted gene flow or nonrandom mating across the two COI lineages of these beetles, rather we hypothesize that historic population structure associated with early Pleistocene climate changes likely contributed to divergent lineages within this species.

DNA barcoding, species-specific PCR and real-time PCR techniques for the identification of six Tribolium pests of stored products

Flour beetles of the genus Tribolium Macleay (Coleoptera: Tenebrionidae) are important stored product pests in China and worldwide. They are often found or are intercepted in grain depots, flour mills, and entry-exit ports, etc. Traditionally, Tribolium species are identified according to the morphological characteristics of the adult. However, it is almost impossible to rapidly identify adult fragments and non-adult stages based on external morphological characteristics. Molecular techniques for the rapid and accurate identification of Tribolium species are required, particularly for pest monitoring and the quarantine of stored products pests. Here, we establish DNA barcoding, species-specific PCR, and real-time PCR techniques for the identification of six stored-product pest Tribolium species including T. castaneum, T. confusum, T. destructor, T. madens, T. freemani and T. brevicornis. We detected the mitochondrial DNA cytochrome oxidase subunit I (COI) barcodes for Tribolium from 18 geographic populations and 101 individuals, built a Tribolium DNA barcode library, and designed species-specific primers and TaqMan probes for the above six Tribolium species. The three techniques were applied to identify Tribolium collected from stored samples and samples captured from quarantine ports. The results demonstrated that three techniques were all able to identify the six species of Tribolium both rapidly and accurately.

Microsatellite markers for Cryptolestes ferrugineus (Coleoptera: Laemophloeidae) and other Cryptolestes species

Cryptolestes ferrugineus (Stephens, 1831) is an important insect pest of stored products. Due to its broad host range, short life cycle, and high reproductive capacity, this species has rapidly colonized temperate and tropical regions around the world. In this study, we isolated 18 novel polymorphic microsatellite loci from an enriched genomic library based on a biotin/streptavidin capture protocol. These loci will be useful tool to better understand the genetic structure and migration patterns of C. ferrugineus throughout the world. The genetic parameters were estimated based on 80 individual C. ferrugineus from two natural populations. The results revealed that 18 loci were different polymorphic levels. The numbers of alleles ranged from 3 to 12, and eleven loci demonstrated polymorphic information contents greater than 0.5. The observed (H O) and expected (H E) heterozygosities ranged from 0.051 to 0.883 and 0.173 to 0.815, respectively. Five locus/population combinations significantly deviated from Hardy-Weinberg equilibrium. We also demonstrated the potential utility of the C. ferrugineus microsatellites as population and species markers for four additional Cryptolestes species.

A molecular framework for the identification of planthopper vectors (Hemiptera: Delphacidae) of central Argentina

Planthoppers are important worldwide crop pests as well as vectors of numerous diseases. Different species transmit Mal de Río Cuarto virus, which causes the most economically important corn disease in central Argentina. Epidemiological studies rely on the accurate identification of the species present in the field. Presently, morphological identification of planthoppers requires taxonomic expertise and there are no taxonomic keys for females and nymphs. Nevertheless, no molecular protocols are available for accurate species identification of most frequent delphacid species from central Argentina. In this context, the aim of this study was to evaluate the utility of the cytochrome oxidase I gene (COI) as a DNA barcode and its digestion with restriction enzymes (Restriction Fragment Length Polymorphism, RFLP) for the identification of the most common species of planthoppers in central Argentina. We amplified and sequenced a 843 bp fragment of the COI gene of taxonomically identified specimens and evaluated its use as a DNA barcode. Restriction enzymes were also selected for digesting the COI fragment via RFLP. The high interspecific variability (20.79%; ± 2.32%) and low intraspecific divergence (0.12%; ± 0.17%) observed in the studied species, demonstrate the effectiveness of the COI gene for species identification of major vector delphacids affecting corn crops in Argentina. Moreover, the digestion of this COI gene fragment with Bfa I and Apo I enzymes allows a fast and cost-effective species identification method when numerous specimens need to be processed. Both molecular techniques developed here, allow the accurate identification of planthopper species at regional scale. These new tools would assist traditional identification of these insects, especially for aiding non-experts in morphological taxonomy.

The complete mitochondrial genome of Cryptolestes turcicus (Grouvelle) (Coleoptera:Laemophloeidae)

We presented the complete mitogenome of Cryptolestes turcicus (GenBank accession number KT070712) in this study. The total length of mitochondrial DNA is 15 517 bp and contains 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes, and a control region. The overall base composition of the genome is A (39.48%), T (37.38%), C (13.97%), and G (9.16%) with an A + T-rich hallmark. The start codon was ATN in all the mitochondrial protein-coding genes, such as ND2, COI, ATP6, ND5, ND4L and ND1 start with ATA, COII, ATP8, ND3, and ND6 genes employing ATT, while the rest using ATG as a start codon. The stop codon was mainly TAA or TAG in most of the mitochondrial protein-coding genes, wherever T(A) was found in COII, COIII, ND4, and ND4L genes. The A + T-rich region is located between 12S rRNA and tRNA(Ile) with a length of 857 bp.

The complete mitochondrial genome of Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae)

We determined the complete mitochondrial genome (mitogenome) sequence of Cryptolestes ferrugineus (GenBank accession number KT182067) by the long PCR and primer walking method. The mitochondrial genome is a typical circular DNA molecule of 15 511 bp in length, and contains 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes, and a A + T-rich region (D-loop). The order of 37 genes was typical of insect mitochondrial DNA sequences described to date. The base composition of the genome is A (39.17%), T (37.24%), C (14.22%), and G (9.37%) with an A + T-rich hallmark as that of other invertebrate mitochondrial genomes. All protein-coding genes start with ATN codon and terminate with the stop codon T (AA) or TAG. The A + T-rich region is located between 12S rRNA and tRNA(Ile). In this study, the phylogenetic relationships of Coleoptera species were constructed based on the nucleotides sequences of 13 PCGs of mitogenomes. The molecular-based phylogeny supported the traditional morphological classification on relationships within Coleoptera species.

COI barcode based species-specific primers for identification of five species of stored-product pests from genus Cryptolestes (Coleoptera: Laemophloeidae)

Flat grain beetles of the genus Cryptolestes (Coleoptera: Laemophloeidae) are one of the economically most important stored-product pests which feed on many kinds of agricultural products, especially grains. Nine of more than 40 described Cryptolestes species are recognized as stored-product pests and two of the pest species have a cosmopolitan distribution. Given the rapid growth in global trade of food products, ecological barriers to the spread of pests are easily overcome. Therefore, development of reliable systems for routine quarantine inspection and early infestation detection is vital. In the present study, we established a new rapid and accurate cytochrome c oxidase subunit I-based system for molecular identification of five common stored-product Cryptolestes species, namely, Cryptolestes capensis, Cryptolestes ferrugineus, Cryptolestes pusilloides, Cryptolestes pusillus and Cryptolestes turcicus. Five species-specific primer pairs for traditional uniplex polymerase chain reaction assay are described and their specificity and sensitivity for the identification process is evaluated using larval samples of 12 different populations from three continents (Asia, Europe and North America).