Papers by BAKTHAVATSALAM NANDAGOPAL
γ-Octalactone is a crucial cue that elicits oviposition in <i>B. dorsalis</i>
<p>(a) Flies were allowed to oviposit into an empty agar disc. Area A contained all EAD act... more <p>(a) Flies were allowed to oviposit into an empty agar disc. Area A contained all EAD active mango cues (cv. Alphonso) at natural ratios except γ-octalactone; Area B contained γ-octalactone alone. Flies could clearly distinguish between the untreated area (A) and the γ-octalactone treated area (B) (One-tailed <i>t</i> test, <i>t</i> = 6.610, <i>df</i> = 8, <i>P</i><0.0001). (b) The mean number of eggs laid into A or B. Oviposition in <i>B. dorsalis</i> was mediated by γ-octalactone. Error bars = Standard error of mean.</p
EAG and ovipositional response of <i>Bactrocera dorsalis</i> to varying concentrations of γ-octalactone
<p>Control = Hexane; SEM: Standard error of mean; Means within a column followed by the sam... more <p>Control = Hexane; SEM: Standard error of mean; Means within a column followed by the same letters <sup>a</sup> or <sup>b</sup> are not significantly different at <i>P</i><0.001 (ANOVA); ppm: parts per million.</p
Schematic representation of the response of flies with different rearing histories towards γ-octalactone. <i>B. dorsalis</i> was reared on 3 different hosts
<p>The final (third) generation gravid females were used in oviposition bioassays. A one-ta... more <p>The final (third) generation gravid females were used in oviposition bioassays. A one-tailed <i>t</i> test revealed a significant difference (<i>P</i><0.0001) between Test (OL, γ-octalactone present) and Control (No OL, γ-octalactone not present). One-way ANOVA between the tests of group 1 (mango), 2 (banana) and 3 (guava) showed no significant difference in the mean no. of eggs laid.</p
γ-Octalactone is an oviposition stimulant and an oviposition site recognition cue
<p>(a) The clear discrimination of the untreated (No OL, γ-octalactone not present) half (A... more <p>(a) The clear discrimination of the untreated (No OL, γ-octalactone not present) half (A) and γ-octalactone treated (OL, γ-octalactone present) half (B) by <i>B. dorsalis</i> in a single plate two-choice assay. (b) Number of eggs laid into treated and untreated pulp (one-tailed paired <i>t</i> test, <i>n</i> = 30, <i>t = </i>11.27, <i>df</i> = 19, <i>P</i><0.0001). Error bars = standard error of mean.</p
Journal of Biological Control, Mar 11, 2013
Maruca vitrata (Fabricius) (Lepidoptera: Crambidae) commonly known as legume pod borer is a pantr... more Maruca vitrata (Fabricius) (Lepidoptera: Crambidae) commonly known as legume pod borer is a pantropical insect pest of many legumes like pigeon pea, field bean, cowpea, greengram, blackgram, soybean and others. The larvae feed on flower buds, flowers, pods, tender parts of stem and peduncles, causing significant yield losses. So far thirty seven species of parasitic wasps have been recorded in association with M. vitrata across the world (Yu, 2012). In the recent rearing records of larval parasitoids from M. vitrata, three species of wasps have been bred,
Arthropod-Plant Interactions, 2017
Herbivore-induced plant volatiles (HIPVs) have been opined as 'indirect or direct defenses' of pl... more Herbivore-induced plant volatiles (HIPVs) have been opined as 'indirect or direct defenses' of plants and are extensively studied. In contrast, HIPVs may also indicate that plant defenses have been overcome by herbivores infesting the plant; however, studies on this aspect have so far received little attention. Using the interaction of Capsicum annum (Bell pepper) with its pest Scirtothrips dorsalis (Chilli thrips) as a model system, we studied the role of HIPVs in this selected insect-plant interaction. Multiple-choice olfactometer assays with headspace volatiles collected from different growth stages of un-infested C. annum plants represented by pre-flowering (PF), flowering (FL) and fruiting stages (FR) proved FR volatiles to be highly attractive to S. dorsalis. Further, FR plants were infested with S. dorsalis adults and HIPVs released by infested plants were collected and subjected to multiple-choice olfactometer bioassays. Thrips were significantly attracted to HIPVs than to headspace volatiles of un-infested FR plants or thrips body odour. Coupled GC-EAG with S. dorsalis and HIPVs or FR plant volatile revealed specific compounds that elicited an EAG response. Individual EAG-active compounds were less attractive to thrips, however, synthetic blends of EAGactive compounds at the ratio similar to headspace samples were found to be highly attractive. However, when given a choice between synthetic blends of HIPVs and FR, thrips were significantly attracted to synthetic blend of HIPVs. Our study provides empirical data on signals HIPVs may provide to conspecific herbivores and suggests that the role of HIPVs, mostly generalized as defense, may vary based on the interaction and must be studied closely to understand their ecological functions.
Behavior and egg-laying response of <i>B. dorsalis</i>
Specific Volatile Compounds from Mango Elicit Oviposition in Gravid Bactrocera dorsalis Females
Journal of Chemical Ecology, 2014
Selecting a suitable oviposition site is crucial to the fitness of female insects because it dete... more Selecting a suitable oviposition site is crucial to the fitness of female insects because it determines the successful development of their offspring. During the oviposition process, an insect must use cues from the external environment to make an appropriate choice of where to lay eggs. Generalist insects can detect and react to a plethora of cues, but are under selection pressure to adopt the most reliable ones to override noise and increase efficiency in finding hosts. The oriental fruit fly, Bactrocera dorsalis (Hendel), is a generalist that utilizes a multitude of fruits as oviposition sites. However, the identity and nature of oviposition stimulants for B. dorsalis is not well known. Recently, we identified a volatile compound γ-octalactone that elicits an innate oviposition response in B. dorsalis. We screened 21 EAD-active volatiles, identified from mango, for their oviposition stimulant activity. 1-Octen-3-ol, ethyl tiglate, and benzothiazole instigated oviposition in gravid B. dorsalis females. Flies deposited most of their eggs into pulp discs with oviposition-stimulants, and only a small fraction of eggs were laid into control discs. In a binary choice oviposition assay, 95.1, 93.7, and 65.6 % of eggs were laid in discs treated with 1-octen-3-ol, ethyl tiglate, and benzothiazole, respectively. Single plate two-choice assays proved that oviposition-stimulants were crucial in oviposition site selection by gravid female B. dorsalis. In simulated semi-natural assays, gravid B. dorsalis females accurately differentiated between fruits with and without 1-octen-3-ol, ethyl tiglate, and γ-octalactone by laying more eggs on the treated fruit. However, benzothiazole did not elicit an increase in oviposition when presented in this context. Our results suggest that the identified oviposition-stimulants are &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;key&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; compounds, which the flies associate with suitable oviposition sites.
Scientific Reports, 2014
Oviposition site-selection in insects is mediated through innate recognition templates (IRTs) tun... more Oviposition site-selection in insects is mediated through innate recognition templates (IRTs) tuned to specific chemical cues. These cues aid gravid insects in choosing suitable oviposition sites and may even enhance the fitness of their offspring by warding off predators and parasitoids. However, studies on the evolution of oviposition site-selection and cues instigating oviposition in domesticated insects remain elusive. Using the interaction between the silkmoth, Bombyx mori, and its host plant mulberry, Morus alba, as a model system, we demonstrate that centuries of domestication of silkmoth has not impaired its oviposition site-selection function. Silkmoths significantly preferred mulberry leaves to filter paper as oviposition sites. Oviposition assays with filter paper, filter paper treated with leaf volatiles and leaf alone proved that surface texture was not a significant criterion for oviposition site-selection, but volatile cues were. Oviposition assays with electrophysiologically active compounds from mulberry revealed that two of the volatiles, valencene and a-humulene, aided moths in choosing suitable oviposition sites and enhanced egg-laying significantly. Moreover, we show that generalist egg-parasitoids are strongly repelled by valencene and a-humulene. Our results demonstrate that IRTs tuned to cues that aid crucial functions like oviposition site-selection are less likely to be impaired even after centuries of domestication.
PLoS ONE, 2014
Innate recognition templates (IRTs) in insects are developed through many years of evolution. Her... more Innate recognition templates (IRTs) in insects are developed through many years of evolution. Here we investigated olfactory cues mediating oviposition behavior in the oriental fruit fly, Bactrocera dorsalis, and their role in triggering an IRT for oviposition site recognition. Behavioral assays with electrophysiologically active compounds from a preferred host, mango, revealed that one of the volatiles tested, c-octalactone, had a powerful effect in eliciting oviposition by gravid B. dorsalis females. Electrophysiological responses were obtained and flies clearly differentiated between treated and untreated substrates over a wide range of concentrations of c-octalactone. It triggered an innate response in flies, overriding inputs from other modalities required for oviposition site evaluation. A complex blend of mango volatiles not containing c-octalactone elicited low levels of oviposition, whereas c-octalactone alone elicited more oviposition response. Naı ¨ve flies with different rearing histories showed similar responses to c-octalactone. Taken together, these results indicate that oviposition site selection in B. dorsalis is mediated through an IRT tuned to c-octalactone. Our study provides empirical data on a cue underpinning innate behavior and may also find use in control operations against this invasive horticultural pest.
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Papers by BAKTHAVATSALAM NANDAGOPAL