DNA barcoding and development of species-specific markers for the identification of tea mosquito bugs (Miridae: Heteroptera) in India

Species-specific markers for Nilaparvata lugens and Sogatella furcifera (Hemiptera: Delphacidae) based on mitochondrial cytochrome oxidase I

Brown planthopper (BPH), Nilaparvata lugens (Stål) and white-backed planthopper (WBPH), Sogatella furcifera (Horváth) are the most destructive sucking insect pests of rice in all rice growing parts of the world. For their accurate identification at early stages, we have developed two species-specific markers (SNL4F and SNL4R for BPH; SNF2F and SNF2R for WBPH) based on mitochondrial cytochrome oxidase I (COI) for their easy detection using Polymerase Chain Reaction (PCR). The markers were developed based on nucleotide differences in COI gene and were subjected to various tests based on PCR-based gel images. The designed primers were cross-checked with five other species, which confirmed their specificity. The primers were also found to be efficient in identification of their respective species (BPH and WBPH) in all the individuals sampled from different regions of India. The lowest detection sensitivity of both the primers was up to 1 ng/µl DNA after testing them through a series of varied DNA concentrations. The species-specific primers developed in this study will help in easy and rapid identification of BPH and WBPH in all the stages of their development and in turn facilitate their timely management.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03693-x.

Multiple species delimitation approaches with COI barcodes poorly fit each other and morphospecies – An integrative taxonomy case of Sri Lankan Sericini chafers (Coleoptera: Scarabaeidae)

DNA taxonomy including barcoding and metabarcoding is widely used to explore the diversity in biodiversity hotspots. In most of these hotspot areas, chafers are represented by a multitude of species, which are well defined by the complex shape of male genitalia. Here, we explore how well COI barcode data reflect morphological species entities and thus their usability for accelerated species inventorization. We conducted dedicated field surveys in Sri Lanka to collect the species‐rich and highly endemic Sericini chafers (Coleoptera: Scarabaeidae). Congruence among results of a series of protocols for de novo species delimitation and with morphology‐based species identifications was investigated. Different delimitation methods, such as the Poisson tree processes (PTP) model, Statistical Parsimony Analysis (TCS), Automatic Barcode Gap Discovery (ABGD), Assemble Species by Automatic Partitioning (ASAP), and Barcode Index Number (BIN) assignments, resulted in different numbers of molecular operational taxonomic units (MOTUs). All methods showed both over‐splitting and lumping of morphologically identified species. Only 18 of the observed 45 morphospecies perfectly matched MOTUs from all methods. The congruence of delimitation between MOTUs and morphospecies expressed by the match ratio was low, ranging from 0.57 to 0.67. TCS and multirate PTP (mPTP) showed the highest match ratio, while (BIN) assignment resulted in the lowest match ratio and most splitting events. mPTP lumped more species than any other method. Principal coordinate analysis (PCoA) on a match ratio‐based distance matrix revealed incongruent outcomes of multiple DNA delimitation methods, although applied to the same data. Our results confirm that COI barcode data alone are unlikely to correctly delimit all species, in particular, when using only a single delimitation approach. We encourage the integration of various approaches and data, particularly morphology, to validate species boundaries.

Determining the position of Diomocoris, Micromimetus and Taylorilygus in the Lygus-complex based on molecular data and first records of Diomocoris and Micromimetus from Australia, including four new species (Insecta : Hemiptera : Miridae : Mirinae)

The Lygus-complex is one of the most taxonomically challenging groups of Miridae (Heteroptera), and its Australian fauna is poorly studied. Here we examine the Australian taxa of the Lygus-complex using morphological and molecular methods. After a detailed morphological study of the material collected throughout Australia, Taylorilygus nebulosus is transferred to Diomocoris, with the genus recorded for the first time in this country. Taylorilygus apicalis, also widely distributed in Australia, is redescribed on the basis of Australian material. The genus Micromimetus is recorded for the first time in Australia, with M. celiae, sp. nov., M. hannahae, sp. nov., M. nikolai, sp. nov. and M. shofneri, sp. nov. described as new to science. Micromimetus pictipes is redescribed and its distributional range is increased. The monophyly of the Lygus-complex and relationships within this group were tested using cytochrome c oxidase subunit I (COI), 16S rRNA, 18S rRNA and 28S rRNA markers. The Lygus-complex has been found to be non-monophyletic. Phylogeny confirmed the monophyly of Micromimetus, and it has shown that Taylorilygus apicalis is closer to Micromimetus species than to Diomocoris nebulosus. This study is the initial step in understanding the Lygus-complex phylogeny; analyses with more taxa, more genes and morphology are needed to reveal the interrelationships within this group, and sister-group relationships of Australian taxa. http://zoobank.org/urn:lsid:zoobank.org:pub:7393D96B-2BBA-438D-A134-D372EFE7FB9E

Evidence for the natural occurrence of Wolbachia in Aedes aegypti mosquitoes

Wolbachia, a Gram-negative bacterium, is widely known to be present in arthropods and nematodes. Of late, great impetus is given to employ this intracellular bacterium, as an alternative to conventional biocontrol agents for the control of mosquitoes because of its inherent ability to induce sperm-egg incompatibility, feminisation etc. By employing molecular tools, we have shown the presence of Wolbachia from Aedes aegypti mosquito population collected from Coimbatore, India by PCR amplifying the Ae. aegypti mosquito genome with Wolbachia specific 16S rRNA, wsp and ftsZ gene primers. The phylogenetic analysis of these gene sequences incorporating MLST and GenBank reference sequences has confirmed the occurrence of Wolbachia supergroup B in Ae. aegypti. In addition, qRT-PCR results have shown the dynamics of Wolbachia across the developmental stages of mosquito. The absence of Wolbachia in tetracycline-treated Ae. aegypti mosquitoes evidenced by transmission electron microscopy reinforced our finding conclusively. After confirming their persistence through generations, we have designated Wolbachia from Ae. aegypti as wAegB. In our considered view, wAegB could play a dynamic role in impeding mosquito multiplication and consequently impinging transmission of the dreadful dengue.

Revisiting DNA barcoding of true bugs of the infraorder Pentatomomorpha (Hemiptera: Heteroptera) from India

Cytochrome c oxidase subunit I gene (COI) sequences of roughly 509 bp length for various species of the Infraorder Pentatomomorpha were generated. K2P divergences within and between species and genera were calculated and compared using newly generated sequences and the ones available on online portals. Mean interspecific (within-genus) genetic divergence (14.23%) was ∼ eight times greater than mean intraspecific (within-species) divergence (1.79%). Distance-based as well as character-based approaches were used towards constructing (COI) trees. In total, 20 sequences were of the species that were previously not part of the Barcode Of Life Database (BOLD), hence representing additions to the barcode library of Indian Heteroptera. Some of the analyzed species are well-known agricultural pests. All the COI sequences and the associated specimen data have been deposited on BOLD.

From water striders to water bugs: the molecular diversity of aquatic Heteroptera (Gerromorpha, Nepomorpha) of Germany based on DNA barcodes

With about 5,000 species worldwide, the Heteroptera or true bugs are the most diverse taxon among the hemimetabolous insects in aquatic and semi-aquatic ecosystems. Species may be found in almost every freshwater environment and have very specific habitat requirements, making them excellent bioindicator organisms for water quality. However, a correct determination by morphology is challenging in many species groups due to high morphological variability and polymorphisms within, but low variability between species. Furthermore, it is very difficult or even impossible to identify the immature life stages or females of some species, e.g., of the corixid genus Sigara. In this study we tested the effectiveness of a DNA barcode library to discriminate species of the Gerromorpha and Nepomorpha of Germany. We analyzed about 700 specimens of 67 species, with 63 species sampled in Germany, covering more than 90% of all recorded species. Our library included various morphological similar taxa, e.g., species within the genera Sigara and Notonecta as well as water striders of the genus Gerris. Fifty-five species (82%) were unambiguously assigned to a single Barcode Index Number (BIN) by their barcode sequences, whereas BIN sharing was observed for 10 species. Furthermore, we found monophyletic lineages for 52 analyzed species. Our data revealed interspecific K2P distances with below 2.2% for 18 species. Intraspecific distances above 2.2% were shown for 11 species. We found evidence for hybridization between various corixid species (Sigara, Callicorixa), but our molecular data also revealed exceptionally high intraspecific distances as a consequence of distinct mitochondrial lineages for Cymatia coleoptrata and the pygmy backswimmer Plea minutissima. Our study clearly demonstrates the usefulness of DNA barcodes for the identification of the aquatic Heteroptera of Germany and adjacent regions. In this context, our data set represents an essential baseline for a reference library for bioassessment studies of freshwater habitats using modern high-throughput technologies in the near future. The existing data also opens new questions regarding the causes of observed low inter- and high intraspecific genetic variation and furthermore highlight the necessity of taxonomic revisions for various taxa, combining both molecular and morphological data.

Genetic assessment of leech species from yak (Bos grunniens) in the tract of Northeast India

Yak is an iconic symbol of Tibet and high altitudes of Northeast India. It is highly cherished for milk, meat, and skin. However, yaks suffer drastic change in milk production, weight loss, etc, when infested by parasites. Among them, infestation by leeches is a serious problem in the Himalayan belt of Northeast India. The parasite feeds on blood externally or from body orifices, like nasopharynx, oral, rectum, etc. But there has been limited data about the leech species infesting the yak in that region because of the difficulties in morphological identification due to plasticity of the body, changes in shape, and surface structure and thus, warrants for the molecular characterization of leech. In anticipation, this study would be influential in proper identification of leech species infesting yak track and also helpful in inventorying of leech species in Northeast India. Here, we investigated, through combined approach of molecular markers and morphological parameters for the identification of leech species infesting yak. The DNA sequences of COI barcode fragment, 18S and 28S rDNA, were analyzed for species identification. The generated sequences were subjected to similarity match in global database and analyzed further through Neighbour-Joining, K2P distance based as well as ML approach. Among the three markers, only COI was successful in delineating species whereas the 18S and 28S failed to delineate the species. Our study confirmed the presence of the species from genus Hirudinaria, Haemadipsa, Whitmania, and one species Myxobdella annandalae, which has not been previously reported from this region.

India's Computational Biology Growth and Challenges

India's computational science is growing swiftly due to the outburst of internet and information technology services. The bioinformatics sector of India has been transforming rapidly by creating a competitive position in global bioinformatics market. Bioinformatics is widely used across India to address a wide range of biological issues. Recently, computational researchers and biologists are collaborating in projects such as database development, sequence analysis, genomic prospects and algorithm generations. In this paper, we have presented the Indian computational biology scenario highlighting bioinformatics-related educational activities, manpower development, internet boom, service industry, research activities, conferences and trainings undertaken by the corporate and government sectors. Nonetheless, this new field of science faces lots of challenges.

The hemiptera (insecta) of Canada: constructing a reference library of DNA barcodes

DNA barcode reference libraries linked to voucher specimens create new opportunities for high-throughput identification and taxonomic re-evaluations. This study provides a DNA barcode library for about 45% of the recognized species of Canadian Hemiptera, and the publically available R workflow used for its generation. The current library is based on the analysis of 20,851 specimens including 1849 species belonging to 628 genera and 64 families. These individuals were assigned to 1867 Barcode Index Numbers (BINs), sequence clusters that often coincide with species recognized through prior taxonomy. Museum collections were a key source for identified specimens, but we also employed high-throughput collection methods that generated large numbers of unidentified specimens. Many of these specimens represented novel BINs that were subsequently identified by taxonomists, adding barcode coverage for additional species. Our analyses based on both approaches includes 94 species not listed in the most recent Canadian checklist, representing a potential 3% increase in the fauna. We discuss the development of our workflow in the context of prior DNA barcode library construction projects, emphasizing the importance of delineating a set of reference specimens to aid investigations in cases of nomenclatural and DNA barcode discordance. The identification for each specimen in the reference set can be annotated on the Barcode of Life Data System (BOLD), allowing experts to highlight questionable identifications; annotations can be added by any registered user of BOLD, and instructions for this are provided.

DNA barcoding of Pentatomomorpha bugs (Hemiptera: Heteroptera) from Western Ghats of India

Recent studies from East Asia and Canadian National Collection of Insects have established the utility of DNA barcoding technique in identification of true bugs. The present study is an expansion of the database by adding mitochondrial cytochrome c oxidase I (mtCOI) sequences from forty three species of indigenous true bugs of India. mtCOI gene analysis of infraorder Pentatomomorpha covering a total of seventy three species that belong to five superfamilies; Pentatomoidea, Coreoidea, Pyrrhocoroidea, Lygaeoidea and Aradoidea revealed more than 3% interspecific distances in all the taxa studied except for two cases which showed barcode sharing. Less than 2% intra-specific divergence was observed in 97% of the taxa analysed and the average interspecies genetic distance was about 29 times higher than the average intraspecies genetic divergence. Distinct sequence divergence pattern at generic level and NJ clustering analysis suggests that COI barcode is an excellent molecular marker for species level identification of unknown taxa; however it may not be useful for resolving deep levels of divergence. Species identification even at nymphal stage could be achieved confirming the efficacy of this technique.

The mitochondrial genome of the plant bug Apolygus lucorum (Hemiptera: Miridae): Presently known as the smallest in Heteroptera

The complete mitochondrial (mt) genome of the plant bug, Apolygus lucorum, an important cotton pest, has been sequenced and annotated in this study. The entire circular genome is 14 768 bp in size and represents the smallest in presently known heteropteran mt genomes. The mt genome is encoding for two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, 13 protein coding genes and a control region, and the order, content, codon usage and base organization show similarity to a great extent to the hypothetical ancestral model. All protein coding genes use standard initiation codons ATN. Conventional stop codons TAA and TAG have been assigned to the most protein coding genes; however, COIII, ND4 and ND5 genes show incomplete terminator signal (T). All tRNA genes possess the typical clover leaf structure, but the dihydrouridine arm of tRNA(Ser(AGN)) only forms a simple loop. Secondary structure models of rRNA genes are generally in accordance with the former models, although some differences exist in certain parts. Three intergenic spacers have never been found in sequenced mt genomes of Heteroptera. The phylogenetic study based on protein coding genes is largely congruent with previous phylogenetic work. Both Bayesian inference and maximum likelihood analyses highly support the sister relationship of A. lucorum and Lygus lineolaris, and Miridae presents a sister position to Anthocoridae.

DNA barcoding and elucidation of cryptic aphid species (Hemiptera: Aphididae) in India

Rapid, precise and timely identification of invasive pest insects such as aphids is important and a challenge worldwide due to their complex life cycles, parthenogenetic reproduction, sex and colour morphs. In this respect, DNA barcoding employing a 658 bp fragment of 5′ region of the mitochondrial cytochrome oxidase I (CO-I) gene is an effective tool in addressing the above. In the present study, we employed CO-I for discriminating 142 individuals representing 32 species of aphids from India. Sequence analyses revealed that the intraspecific and interspecific distances ranged from zero to 3.8% and 2.31 to 18.9%, respectively. In addition, the study also showed for the first time the prevalence of three cryptic species, namely Brevicoryne brassicae (Linnaeus), Hyperomyzus carduellinus (Theobald) and Brachycaudus helichrysi (Kaltenbach) from India. Our work has clearly demonstrated that DNA barcoding is an efficient and accurate method for identification of aphid species (including cryptic species), an approach that potentially could play an important role in formulating viable pest management strategies, more especially biocontrol.