Browsing by Author "Kesavan Subaharan"

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Antennal sensilla architecture of Thrips parvispinus (Karny) and Thrips subnudula (Karny) infesting chillies, Capsicum annuum L.: insights from scanning electron microscopy
(Springer Science and Business Media Deutschland GmbH, 2025) Chandrasekaran Praveenkumar; Saminathan Vangili Ramasamy; Remani Remani Rachana; Kesavan Subaharan; Preetha Gnanadhas; Selvam Saravanan; Subrata Goswami; Amala Udayakumar; Sampathrajan Vellaikumar; Chinnasamy Kavitha; Satya Nand Sushil
Invasive chilli thrips, Thrips parvispinus (Karny) coexists with Thrips subnudula (Karny) on chillies, Capsicum annuum L. causing damage to the flowers and leaves. Thrips rely on olfactory cues for host selection, mating and oviposition. Olfaction in thrips is mediated by a pair of antennae with sensilla distributed on its surface to perceive the olfactory stimuli. As both T. parvispinus and T. subnudula share chilli as their host, a comparative analysis was done between the two species to establish the morphology and distribution of antennal sensilla using scanning electron microscopy (SEM). In both the species, nine types of sensilla: Böhm bristles (BB), sensilla basiconica (SBI, SBII, SBIII), sensilla chaetica (SChI, SChII), sensilla coeloconica (SCo), sensilla trichoidea (ST), sensilla campaniformia (SCa), sensilla cavity (SCav), sensilla mammillary (SM) and micro trichia (MT) were identified. Although the sensilla arrangement was similar in both species, T. parvispinus had longer antennae and larger sensilla especially those linked to olfactory and thermo-hygrosensory functions indicating sensory adaptations for more complex host-seeking behavior. In contrast, T. subnudula, despite sharing common host (chilli), exhibited relatively smaller and less elaborated sensilla structures, reflecting its limited ecological niche. This study will add to the information on the morphological foundation of the antennae which could be used to elucidate the olfactory mechanisms in two species of thrips mentioned above. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025.
Evaluation of predatory potential and prey stage preference of mirid bug, Nesidiocoris tenuis on tomato pinworm, Tuta absoluta
(Springer Science and Business Media Deutschland GmbH, 2021) Rajendran Dhanapal; Rajendra Nath Singh; Mahadevan Raghuraman; Muthugounder Mohan; Kesavan Subaharan; Manivannan Hemavathi
Mirid bug, Nesidiocoris tenuis is a voracious predatory bug that is spontaneously present in horticultural crops. Recently, it has been reported and practiced as a biocontrol agent against several insect pests. In the present study, we have evaluated mirid bug’s predatory potential against Tuta absoluta developmental stages. Eggs, 1st, 2nd and 3rd larval instars of T. absoluta were seemingly the most preferred by all feeding stages of the mirid bugs. The 4th larval instar and pupae of T. absoluta were not pre-selected to feed during any stage of N. tenuis. As the T. absoluta immature stages grew in size, their total prey consumption decreased. The olfactory bioassay was performed for the adults of N. tenuis against tomato plants infested with various developmental stages of T. absoluta, using a Y-tube olfactometer. The results revealed that the early stages of T. absoluta, especially eggs emit volatiles to allure the N. tenuis adults. These outcomes enriched the resources for mass rearing of N. tenuis and their efficacy in the field, which will undoubtedly aid the farmers in the prevention of crop damage due to pests and control the tomato pinworm. © 2021, Institute of Zoology, Slovak Academy of Sciences.
Integrating electrophysiology, behavioral response, and docking studies to decipher odorant-binding protein function in the brinjal shoot and fruit borer, Leucinodes orbonalis Guenee
(Springer Science and Business Media Deutschland GmbH, 2025) Selvam Saravanan; P. S. Shanmugam; Kesavan Subaharan; M. Murugan; Kolanchi Prakash; Karuppannasamy Ashok; Chandrasekaran Praveenkumar; Subrata Goswami; T. Srinivasan; Thiyagarajan Elaiyabharathi; Sampathrajan Vellaikumar
The brinjal shoot and fruit borer, Leucinodes orbonalis Guenée, inflicts significant yield losses in brinjal, often resulting in the extensive use of insecticides. Development of insecticide resistance and ecological concerns demand safer and species-specific alternatives. This study examines plant-derived volatile organic compounds (VOCs) as potential semiochemicals for its management. The present study employed electroantennography (EAG) to examine the summated neuronal response in the antennal of unmated male and female L. orbonalis moths to host plant VOCs. Both male and female antennae showed higher response when exposed to nonanal, α-terpineol, 2-ethyl-1-hexanol, linalool, methyl salicylate, and phenylacetaldehyde, with females showing greater sensitivity than males. The behavioral assays using a Y-tube olfactometer demonstrated significant attraction of moths towards 2-ethyl-1-hexanol, benzaldehyde, and phenylacetaldehyde. To further substantiate these findings, molecular docking studies were conducted using homology models of general odorant-binding proteins (GOBPs: GOBP1, GOBP2, and GOBP3) of L. orbonalis. Protein models were constructed through MODELLER, validated for structural accuracy, and docked with selected VOCs obtained from PubChem using AutoDock Vina. Among the three proteins, GOBP2 displayed the strongest and broadest ligand-binding affinities, followed by GOBP3 and GOBP1. Notably, high-affinity interactions with 2-ethyl-1-hexanol, benzaldehyde, and phenylacetaldehyde were characterized by π–π stacking, van der Waals forces, and hydrophobic bonding. The docking outcomes correspond closely with EAG and behavioral results, underscoring the potential of these VOCs as eco-friendly semiochemicals based management of L. orbonalis. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025.
Integrative taxonomy of thrips infesting chilli in India: Morphological and molecular insights
(Springer Science and Business Media B.V., 2025) Chandrasekaran Praveenkumar; Saminathan Vangili Ramasamy; Remani Remani Rachana; Gandhi Ramasamy Gracy; Kesavan Subaharan; Preetha Gnanadhas; Sengottayan Senthil-Nathan; Selvam Saravanan; Subrata Goswami; Sampathrajan Vellaikumar; Chinnasamy Kavitha; Johnsi Lenin
Simultaneous infestation by multiple thrips species poses a major challenge in the cultivation of chillies (Capsicum annuum L.). Accurate identification of thrips species is essential for formulating effective management strategies. Identification of thrips is commonly done using the morphological characters, but adoption of molecular tools in tandem with morphological features will be an integrative approach for correct identification. Chillies are infested by an array of thrips species. In the current study, eight species of thrips infesting chillies across India were identified. Among them Thrips parvispinus Karny (48%) and Scirtothrips dorsalis Hood (24%) Hood were most prevalent. Identification of thrips species was confirmed using morphological features and DNA barcoding, showing close matches with entries in the Barcode of Life Data System (BOLD). Phylogenetic analysis revealed distinct clades for each species. Thrips subnudula (Karny), a first record from our observation in India infesting C. annuum was genetically distinct. Barcode divergence analysis indicated moderate intraspecific variation in T. parvispinus, with high variation and haplotype richness in S. dorsalis, and low variation in T. subnudula, which showed genetic uniformity. Analysis of molecular variance (AMOVA) showed 48.57% of genetic variation among populations and 51.43% within populations (Fst = 0.48569), indicating moderate genetic differentiation. These findings highlight the need for periodic surveillance of thrips species to monitor their distribution and genetic diversity that would enable in formulating effective management strategies for thrips infesting chillies. © The Author(s), under exclusive licence to Springer Nature B.V. 2025.