Synergistic and additive interactions of Shewanella sp., Pseudomonas sp. and Thauera sp. with chlorantraniliprole and emamectin benzoate for controlling Spodoptera litura (Fabricius).

The imprudent use of insecticides causes the development of resistance in insect pest populations, contamination of the environment, biological imbalance and human intoxication. The use of microbial pathogens combined with insecticides has been proposed as an alternative strategy for insect pest management. This IPM approach may offer effective ways to control pests, in addition to lowering the risk of chemical residues in the environment. Spodoptera litura (Fabricius) is a major pest of many crops like cotton, maize, tobacco, cauliflower, cabbage, and fodder crops globally. Here, we evaluated the combined effects of new chemistry insecticides (chlorantraniliprole and emamectin benzoate) and entomopathogenic bacterial strains, Shewanella sp. (SS4), Thauera sp. (M9) and Pseudomonas sp. (EN4) against S. litura larvae inducing additive and synergistic interactions under laboratory conditions. Both insecticides produced higher larval mortality when applied in combination with bacterial isolates having maximum mortality of 98 and 96% with LC50 of chlorantraniliprole and emamectin benzoate in combination with LC50 of Pseudomonas sp. (EN4) respectively. The lower concentration (LC20) of both insecticides also induced synergism when combined with the above bacterial isolates providing a valuable approach for the management of insect pests. The genotoxic effect of both the insecticides was also evaluated by conducting comet assays. The insecticide treatments induced significant DNA damage in larval hemocytes that further increased in combination treatments. Our results indicated that combined treatments could be a successful approach for managing S. litura while reducing the inappropriate overuse of insecticides.

Impact of Plant Symbiotic Endophytic Fungus, Aspergillus terreus on Insect Herbivore Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae).

Herbivorous insects are known to be resistant to fungal endophytes that asymptomatically inhabit plant tissues. The insecticidal ability of the endophytic fungus Aspergillus terreus isolated from Catharanthus roseus against Spodoptera litura (Fabricius) was assessed in the current study. The survival and growth of S. litura were adversely impacted by the ethyl acetate extract of endophytic A. terreus. Fungal extract supplemented diet caused 14 to 94% larval mortality in comparison to 2% in control. Additionally, retarded insect growth was observed after ingestion of supplemented diet. The fungal metabolites were also observed to have an inhibitory influence on the adult emergence and reproductive potential of adults. Phytochemical analysis revealed the presence of phenolic compounds in the crude extract of endophytic fungus which may be responsible for toxicity. It was also determined how endophyte-infected cauliflower plants affected S. litura's survival and growth. Endophyte-infected plants exhibited resistance to S. litura by causing 54% larval mortality and delaying development by 5.2 days. In comparison to uninfected plants, adult emergence, lifespan, fecundity and egg hatchability of insects was significantly decreased on infected plants. There was a significant decrease in relative growth and consumption rates as well as in the efficiency of food conversion, which indicates toxic and antifeedant effect of the fungus on S. litura. This suggests that endophyte-inoculated plants exhibit antibiosis against S. litura. In conclusion, the endophytic fungi having insecticidal activity could be used to develop alternative ecologically safe control strategies.

Beyond Molecular Recognition: A Perylene Bisimide Derivative as a Functional Mimic of Chlorpyrifos.

Supramolecular assemblies of perylene bisimide derivative (PBI-SAH) have been developed which show 'turn-on' detection of chlorpyrifos in aqueous media, apple residue and blood serum. Differently from the already reported fluorescent probes for the detection of CPF, PBI-SAH assemblies also show affinity for acetylcholinesterase (AChE) which endow the PBI-SAH molecules with mixed inhibitory potential to restrict the AChE catalysed hydrolysis of acetylthiocholine (ATCh) in MG-63 cell lines (in vitro) and in mice (in vivo). The molecular docking studies support the inhibitory activity of PBI-SAH assemblies and their potential to act as safe insecticide with high benefit to harm ratio. The insecticidal potential of PBI-SAH derivative has been examined against Spodoptera litura (S. litura) and these studies demonstrate its excellent insecticidal activity (100 % mortality in nineteen days). To the best of our knowledge, this is the first report regarding development of PBI-SAH assemblies which not only detect chlorpyrifos but also mimic AChE inhibitory activity of CPF to show promising aptitude as safe insecticide.

Larvicidal, growth inhibitory and biochemical effects of soil bacterium, Pseudomonas sp. EN4 against Spodoptera litura (Fab.) (Lepidoptera: Noctuidae).

BACKGROUND: Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) also known as tobacco caterpillar, is one of the most serious polyphagous pests that cause economic losses to a variety of commercially important agricultural crops. Over the past few years, many conventional insecticides have been used to control this pest. However, the indiscriminate use of these chemicals has led to development of insecticide resistant populations of S. litura in addition to harmful effects on environment. Due to these ill effects, the emphasis is being laid on alternative eco-friendly control measures. Microbial control is one of the important components of integrated pest management. Thus, in search for novel biocontrol agents, the current work was carried out with the aim to evaluate the insecticidal potential of soil bacteria against S. litura. RESULTS: Among the tested soil bacterial isolates (EN1, EN2, AA5, EN4 and R1), maximum mortality (74%) was exhibited by Pseudomonas sp. (EN4). The larval mortality rate increased in a dose-dependent manner. Bacterial infection also significantly delayed the larval development, reduced adult emergence, and induced morphological deformities in adults of S. litura. Adverse effects were also detected on various nutritional parameters. The infected larvae showed a significant decrease in relative growth and consumption rate as well as efficiency of conversion of ingested and digested food to biomass. Histopathological studies indicated damage to the midgut epithelial layer of larvae due to the consumption of bacteria treated diet. The infected larvae also showed a significantly decreased level of various digestive enzymes. Furthermore, exposure to Pseudomonas sp. also caused DNA damage in the hemocytes of S. litura larvae. CONCLUSION: Adverse effects of Pseudomonas sp. EN4 on various biological parameters of S. litura indicate that this soil bacterial strain may be used as an effective biocontrol agent against insect pests.

The genotoxic, cytotoxic and growth regulatory effects of plant secondary metabolite ß-caryophyllene on polyphagous pest Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae).

Use of secondary metabolites as an alternative to organic pesticides is an eco-friendly and safe strategy in pest management. ß-caryophyllene [(1R,4E,9S)-4,11,11-trimethyl-8-methylene bicyclo [7.2.0]undec-4-ene], a natural sesquiterpene is found as an essential oil in many plants like Syzygium aromaticum, Piper nigrum, Cannabis sativa. The present study aims at exploring the insecticidal, genotoxic and cytotoxic potential of ß-caryophyllene against common cutworm Spodoptera litura (Fab.), a major polyphagous pest. S. litura larvae were fed on different concentrations (5, 25, 125, 625 and 3125 ppm) of ß-caryophyllene. Results revealed delay in larval and pupal period with increase in concentration. Larval mortality increased and adult emergence declined significantly with increase in concentration. Higher concentrations of ß-caryophyllene caused pupal and adult deformities. A negative impact of ß-caryophyllene was also seen on the nutritional physiology of S. litura. Parameters such as relative growth rate, relative consumption rate, efficiency of conversion of ingested food, efficiency of conversion of digested food and approximate digestibility showed a significant reduction in a dose dependent manner. DNA damage assessed using comet assay revealed significant genotoxic effects at LC30 and LC50 concentrations. There was an increase in tail length, percent tail DNA, tail moment and olive tail moment. Phenol oxidase activity was suppressed at LC50 concentration with respect to control. Total hemocyte count also declined significantly at LC30 and LC50 concentrations as compared to control. ß-caryophyllene induced genotoxic and cytotoxic damage affecting the growth and survival of S. litura larvae. Our findings suggest that ß-caryophyllene has the potential to be used for the management of insect pests.

Assessing the pathogenicity of gut bacteria associated with tobacco caterpillar Spodoptera litura (Fab.).

The symbiotic relationship between insects and gut microbes contributes to their fitness by serving immense range of functions viz. nutrition and digestion, detoxification, communication and reproduction etc. However, this relationship between insect and gut microbes varies from mutualistic to pathogenic. Gut microbes become pathogenic when the healthy normal microbial composition is perturbed leading to the death of insect host. Spodoptera litura (Fab.) is a polyphagous pest that causes significant damage to many agricultural crops. The management of this pest primarily depends upon chemical insecticides which have resulted in development of resistance. Thus in search for alternative strategies, culturable gut bacteria isolated from S. litura were screened for insecticidal potential. Among these Serratia marcescens and Enterococcus mundtii induced higher larval mortality in S. litura. The mortality rate increased from 32 to 58% due to S. marcescens at concentrations ranging from 2.6 × 108 to 5.2 × 109 cfu/ml and 26 to 52% in case of E. mundtii due to increase in concentration from 4.6 × 108 to 6.1 × 109 cfu/ml. Both the bacteria negatively affected the development, nutritional physiology and reproductive potential of insect. The results indicated a change in gut microbial composition as well as damage to the gut epithelial membrane. Invasion of gut bacteria into the haemocoel led to septicaemia and ultimately death of host insect. In conclusion both these gut bacteria may serve as potential biocontrol agents against S. litura.

Insecticidal and growth inhibitory activity of gut microbes isolated from adults of Spodoptera litura (Fab.).

BACKGROUND: Spodoptera litura (Fab.) (Lepidoptera: Noctuidae) commonly known as tobacco caterpillar is a polyphagous pest that causes significant damage to many agricultural crops. The extensive use of chemical insecticides against S. litura has resulted in development of resistance. In order to find potential biocontrol agents, gut microbes were investigated for insecticidal potential. These microbes live in a diverse relationship with insects that may vary from beneficial to pathogenic. RESULTS: Enterococcus casseliflavus, Enterococcus mundtii, Serratia marcescens, Klebsiella pneumoniae, Pseudomonas paralactis and Pantoea brenneri were isolated from adults of S. litura. Screening of these microbial isolates for insecticidal potential against S. litura showed higher larval mortality due to K. pneumoniae and P. paralactis. These bacteria also negatively affected the development of insect along with significant decline in relative growth and consumption rate as well as efficiency of conversion of ingested and digested food of insect. The bacteria significantly decreased the reproductive potential of insect. Perturbations in the composition of gut microbiome and damage to gut epithelium were also observed that might be associated with decreased survival of this insect. CONCLUSIONS: Our study reveals the toxic effects of K. pneumoniae and P. paralactis on biology of S. litura. These bacteria may be used as potential candidates for developing ecofriendly strategies to manage this insect pest.

Aspergillus flavus induced oxidative stress and immunosuppressive activity in Spodoptera litura as well as safety for mammals.

BACKGROUND: In the last few decades, considerable attention has been paid to entomopathogenic fungi as biocontrol agents, however little is known about their mode of action and safety. This study aimed to investigate the toxicity of Aspergillus flavus in insect Spodoptera litura by analyzing the effect of fungal extract on antioxidant and cellular immune defense. In antioxidant defense, the lipid peroxidation (Malondialdehyde content) and antioxidant enzymes activities (Catalase, Ascorbate peroxidase, Superoxide dismutase) were examined. In cellular immune defense, effect of A. flavus extract was analyzed on haemocytes using Scanning Electron Microscopy (SEM). Furthermore, mammalian toxicity was analyzed with respect to DNA damage induced in treated rat relative to control by comet assay using different tissues of rat (blood, liver, and kidney). RESULTS: Ethyl acetate extract of A. flavus was administrated to the larvae of S.litura using artificial diet method having concentration 1340.84 µg/ml (LC50 of fungus). The effect was observed using haemolymph of insect larvae for different time intervals (24, 48, 72 and 96). In particular, Malondialdehyde content and antioxidant enzymes activities were found to be significantly (p ≤ 0.05) increased in treated larvae as compared to control. A. flavus ethyl acetate extract also exhibit negative impact on haemocytes having major role in cellular immune defense. Various deformities were observed in different haemocytes like cytoplasmic leakage and surface abnormalities etc. Genotoxicity on rat was assessed using different tissues of rat (blood, liver, and kidney) by comet assay. Non-significant effect of A. flavus extract was found in all the tissues (blood, liver, and kidney). CONCLUSIONS: Overall the study provides important information regarding the oxidative stress causing potential and immunosuppressant nature of A. flavus against S. litura and its non toxicity to mammals (rat), mammals (rat), suggesting it an environment friendly pest management agent.

Effect of gallic acid on the larvae of Spodoptera litura and its parasitoid Bracon hebetor.

The antibiosis effect of gallic acid on Spodoptera litura F. (Lepidoptera: Noctuidae) and its parasitoid evaluated by feeding six days old larvae on artificial diet incorporated with different concentrations (5 ppm, 25 ppm, 125 ppm, 625 ppm, 3125 ppm) of the phenolic compound revealed higher concentration (LC50) of gallic acid had a negative impact on the survival and physiology of S. litura and its parasitoid Bracon hebetor (Say) (Hymenoptera:Braconidae). The mortality of S. litura larvae was increased whereas adult emergence declined with increasing concentration of gallic acid. The developmental period was delayed significantly and all the nutritional indices were reduced significantly with increase in concentration. Higher concentration (LC50) of gallic acid adversely affected egg hatching, larval mortality, adult emergence and total development period of B. hebetor. At lower concentration (LC30) the effect on B. hebetor adults and larvae was non-significant with respect to control. Gene expression for the enzymes viz., Superoxide dismutase, Glutathione peroxidase, Peroxidase, Esterases and Glutathione S transferases increased while the total hemocyte count of S. litura larvae decreased with treatment. Our findings suggest that gallic acid even at lower concentration (LC30) can impair the growth of S. litura larvae without causing any significant harm to its parasitoid B. hebetor and has immense potential to be used as biopesticides.

Schizophyllum commune induced oxidative stress and immunosuppressive activity in Spodoptera litura.

BACKGROUND: In the last few decades, considerable attention has been paid to fungal endophytes as biocontrol agents, however little is known about their mode of action. This study aimed to investigate the toxic effects of an endophytic fungus Schizophyllum commune by analyzing activities of antioxidant and detoxifying enzymes as well as morphology of haemocytes using Spodoptera litura as a model. RESULTS: Ethyl acetate extract of S. commune was fed to the larvae of S. litura using the artificial diet having 276.54 µg/ml (LC50 of fungus) concentration for different time durations. Exposed groups revealed significant (p ≤ 0.05) increase in the activities of various enzymes viz. Catalase, Ascorbate peroxidase, Superoxide dismutase, Glutathione-S-Transferase. Furthermore, haemocytes showed various deformities like breakage in the cell membrane, cytoplasmic leakage and appearance of strumae in the treated larvae. A drastic reduction in the percentage of normal haemocytes was recorded in the treated groups with respect to control. CONCLUSION: The study provides important information regarding the oxidative stress causing and immunosuppressant potential of S. commune against S. litura and its considerable potential for incorporation in pest management programs.

Effect of α-glycosidase inhibitors from endophytic fungus Alternaria destruens on survival and development of insect pest Spodoptera litura Fab. and fungal phytopathogens.

In the present study the production of α-glycosidase inhibitors was used as a strategy to screen endophytic fungi with insecticidal and antifungal potential. Endophytic fungi were isolated from Calotropis gigantea L. (Gentianales: Apocynaceae) and evaluated for their α-glycosidase inhibitory activity. Maximum inhibitory activity was observed in an isolate AKL-3, identified to be Alternaria destruens E.G.Simmons on the basis of morphological and molecular analysis. Production of inhibitory metabolites was carried out on malt extract and partially purified using column chromatography. Insecticidal potential was examined on Spodoptera litura Fab. (Lepidoptera: Noctudiae). Partially purified α-glycosidase inhibitors induced high mortality, delayed the development period as well as affected the adult emergence and induced adult deformities. Nutritional analysis revealed the toxic and antifeedant effect of AKL-3 inhibitors on various food utilization parameters of S. litura. They also inhibited the in vivo digestive enzymes activity in S. litura. Partially purified α-glycosidase inhibitors were also studied for their antifungal potential. Inhibitors demonstrated antifungal activity against the tested phytopathogens inducing severe morphological changes in mycelium and spores. This is the first report on production of α-glycosidase inhibitors from A. destruens with insecticidal and antifungal activity. The study also highlights the importance of endophytes in providing protection against insect pests and pathogens to the host.

Effect of crude extracts and purified compounds of Alpinia galanga on nutritional physiology of a polyphagous lepidopteran pest, Spodoptera litura (Fabricius).

Secondary plant metabolites play an important role in providing protection to plants against herbivore insect pests. Keeping in view the increasing importance of biopesticides, the crude extracts from different plants are being investigated for insecticidal activities. Alpinia galanga, a medicinal plant belonging to family Zingiberaceae exhibits a wide range of biological activities. In the present study, crude extracts of A. galanga and its purified compounds i.e. 1'-acetoxychavicol acetate and galangin were evaluated for their effect on various nutritional parameters of Spodoptera litura (Fab.). All the extracts exhibited a significant influence on relative growth and consumption rates as well as efficiency of conversion of ingested and digested food. Ethyl acetate extract was found to be the most effective causing significant reduction in values of RGR, RCR, ECI and ECD of S. litura larvae in comparison to control larvae. The highest concentration of the ethyl acetate extract (2500 ppm) resulted in 44.95%, 10.99%, 38.08% and 37.04% decrease respectively in RGR, RCR, ECI and ECD in comparison to control. The purified compounds also showed inhibitory effects on various nutritional parameters. 1'-Acetoxychavicol acetate was found to be more effective in comparison to galangin.

Schizophyllum commune induced genotoxic and cytotoxic effects in Spodoptera litura.

In search for ecofriendly alternatives to chemical insecticides the present study was conducted to assess the insecticidal potential of an endophytic fungus Schizophyllum commune and its mechanism of toxicity by studying genotoxic and cytotoxic effects as well as repair potential using Spodoptera litura (Fabricius) as a model. Different endophytic fungi were isolated and tested for their insecticidal potential against S. litura. Among the tested endophytic fungi maximum mortality against S. litura was exhibited by S. commune isolated from Aloe vera. Extended development, reduced adult emergence was observed in larvae fed on diet supplemented with fungal extract. In addition to it the fungus also has propensity to increase oxidative stress which leads to significantly higher DNA damage. The significantly lower frequency of living haemocytes and increased frequency of apoptotic and necrotic cells was also observed in larvae treated with fungal extract. The extent of recovery of damage caused by fungus was found to be very low indicating long term effect of treatment. Phytochemical analysis revealed the presence of various phenolics, terpenoids and protein in fungal extract. Biosafety analysis indicated the non toxic nature of extract. This is the first report showing the insecticidal potential of S. commune and the genotoxic and cytotoxic effects associated with it.

Evaluation of Bacillus vallismortis (Bacillales: Bacillaceae) R2 as insecticidal agent against polyphagous pest Spodoptera litura (Lepidoptera: Noctuidae).

The insecticidal potential of cells and acid-precipitated biomolecules (APB) of Bacillus vallismortis (Roberts) (Bacillales: Bacillaceae) R2 was evaluated against polyphagous pest Spodoptera litura. The intact cells of isolate R2 and its APB preparation significantly increased larval mortality. Both cells and APB significantly delayed the development and reduced adult emergence of S. litura. The toxicity of isolate R2 was evident from the emergence of morphologically deformed adults with crumpled and underdeveloped wings. The nutritional physiology of larvae fed on APB-supplemented diet was also adversely affected resulting in significant reduction of relative growth and consumption rate as well as efficiency of conversion of ingested and digested food. Thus, the intact viable cells and APB of B. vallismortis R2 may serve as environmental-friendly alternatives to chemical insecticides.

Impact of sesquiterpenes from Inula racemosa (Asteraceae) on growth, development and nutrition of Spodoptera litura (Lepidoptera: Noctuidae).

BACKGROUND: The use of botanical pesticides for protecting crops from insect pests has assumed greater importance all over the world owing to growing awareness of harmful effects of indiscriminate use of synthetic pesticides. Inula racemosa Hook. f. (Asteraceae), a medicinally important perennial herb, is rich in sesquiterpenes with many biological activities. The present studies were conducted with the objective to evaluate the sesquiterpenes isolated from I. racemosa for insecticidal activity against Spodoptera litura (F.). RESULTS: Alantolactone and isoalantolactone isolated from I. racemosa exerted growth inhibitory effects on S. litura. Addition of both the sesquiterpenes to larval diet extended the development period and reduced pupation as well as adult emergence. The dietary utilisation experiments on third-instar larvae of S. litura revealed reduction in consumption and growth rates of larvae as well as efficiency of conversion of ingested and digested food owing to alantolactone and isoalantolactone. CONCLUSION: The root extract of I. racemosa, which is rich in two sesquiterpenes, i.e. alantolactone and isoalantolactone, has the potential for management of S. litura. However, there is a need to understand the specific mechanism of action of these compounds. © 2016 Society of Chemical Industry.

Insecticidal potential of an endophytic Cladosporium velox against Spodoptera litura mediated through inhibition of alpha glycosidases.

Alpha glucosidase inhibitory activity was exhibited by partially purified fractions obtained from an endophytic Cladosporium velox, isolated from Tinospora cordifolia. Taking into account the increasing importance of digestive enzyme inhibitors as insecticidal agents, the entomopathogenic potential of the fractions obtained was evaluated against Spodoptera litura (Fab.), a polyphagous pest. Considerable mortality was obtained when the larvae were fed on diet supplemented with the partially purified extract. All the concentrations of the extract significantly prolonged the overall developmental period of S. litura. At higher concentrations, the extract influenced the longevity of females as well as their reproductive potential. Phytochemical analysis revealed the presence of phenolic compounds in the active fraction. The phenolic compound responsible for the bioactivities was purified and identified to be chlorogenic acid using HPLC and MS analysis. The content of chlorogenic acid in the extract was quantified to be 250µg/ml. The purified compound also demonstrated inhibition of alpha glycosidases in vivo. The present study indicates that the endophyte imparted resistance to the insects in the plants could be mediated through chlorogenic acid targeting the alpha glycosidases present in the gut of the insect. The isolate obtained can be exploited for the production of chlorogenic acid, which has the potential to be exploited as a biocontrol agent against S. litura.

Endophyte-mediated interactions between cauliflower, the herbivore Spodoptera litura, and the ectoparasitoid Bracon hebetor.

Fungal endosymbionts in plants may influence interactions among plants, herbivores and their parasitoids through the production of secondary metabolites. We used a lepidopteran pest and its generalist parasitoid to test the effect of endophyte-infected plants on a third trophic level. Endophytic fungi, Aspergillus flavus and Aspergillus niger, isolated from Acacia arabica, were used to infect cauliflower plants. We found that the presence of the endophyte in the plants significantly extended the development period of Spodoptera litura (Fab.) larvae. Feeding of the host on endophyte-infected plants further adversely affected the development and performance of its parasitoid, Bracon hebetor (Say). A negative impact was also recorded for longevity and fecundity of endophyte-naive parasitoid females due to the parasitization of host larvae fed on endophyte-infected plants. The presence of endophytes in the diet of the host larvae significantly prolonged the development of the parasitoid. A strong detrimental effect was also recorded for larval survival and emergence of parasitoid adults. The longevity and parasitism rate of female wasps were reduced significantly due to the ingestion of endophyte-infected cauliflower plants by S. litura larvae. Overall, we found that both endophytic fungi had a negative impact on the parasitoid.

Pathogenicity of bacteria isolated from gut of Spodoptera litura (Lepidoptera: Noctuidae) and fitness costs of insect associated with consumption of bacteria.

Gut microbes contribute to the health of insects and perturbations in the composition or location of gut microbiota can lead to pathological states and host mortality. We explored the culturable bacterial community in the gut of Spodoptera litura (Fab.) larvae, which is a polyphagous pest. Bacterial isolates were identified as Microbacterium arborescens (SL6), Enterococcus casseliflavus (SL10) and Enterobacter cloacae (SL11) by using culture dependent technique based on 16S rRNA gene sequencing. Screening of these three isolates for insecticidal potential against the same host i.e. S. litura indicated the highest larval mortality in E. cloacae (73.33%). Further, we assessed the effect of E. cloacae (SL11) infection on growth and development of S. litura. A significant effect of E. cloacae was observed on various biological parameters viz. larval and pupal period, total development period and reproductive potential of S. litura. E. cloacae significantly influenced the immune response of S. litura. A marked decrease in total hemocyte count was observed in larvae infected with E. cloacae whereas lysozyme and phenoloxidase activity increased initially followed by a decline. The gut microbial diversity in larvae infected with E. cloacae differed from control larvae. The population of E. cloacae in the gut of infected larvae exceeded over the other two microbes and resulted in pathogenicity and death of S. litura larvae. This indicates that E. cloacae can have the potential to be used as a promising biological control agent.

An alpha-glucosidase inhibitor from an endophytic Cladosporium sp. with potential as a biocontrol agent.

This study highlights the importance of alpha-glucosidase inhibitors as mechanisms for endophyte-mediated resistance to insect pests. One of the major benefits which endophytes confer on plants is providing resistance against insect pests. This built-in defense mechanism of the plant can be used for exploring ecofriendly strategies for pest control. In the present study, 34 endophytic fungi were isolated from Tinospora cordifolia and screened for their ability to produce alpha-glucosidase inhibitors. Maximum inhibitory activity was observed in an isolate from T. cordifolia (TN-9S), identified to be Cladosporium sp. The inhibitor was purified using chromatographic techniques. The insecticidal activity of the purified inhibitor was evaluated against Spodoptera litura. The inhibitor induced a significant mortality in the larvae of S. litura and adversely affected its survival and development. It also inhibited the activity of α-glycosidases in vivo in the gut of the larvae. The purified inhibitor was determined to be a phenolic compound with amine groups, demonstrating a noncompetitive type of inhibition in vitro. The production of the inhibitor was optimized. Response surface methodology (RSM) analysis revealed a significant interaction between dextrose and malt extract, with first-order effect of pH.

Enhanced resistance to Spodoptera litura in endophyte infected cauliflower plants.

Endophytic fungi, which live within host plant tissues without causing any visible symptom of disease, are important mediators of plant-herbivore interactions. These endophytes enhance resistance of host plant against insect herbivores mainly by productions of various alkaloid based defensive compounds in the plant tissue or through alterations of plant nutritional quality. Two endophytic fungi, i.e., Nigrospora sp. and Cladosporium sp., were isolated from Tinospora cordifolia (Thunb.) Miers, a traditional indian medicinal plant. Cauliflower (Brassica oleracea L.) plants were inoculated with these two endophytic fungi. The effect of endophyte infected and uninfected cauliflower plants were measured on the survival and development of Spodoptera litura (Fab.), a polyphagous pest. Endophyte infected cauliflower plants showed resistance to S. litura in the form of significant increase in larval and pupal mortality in both the fungi. Inhibitory effects of endophytic fungi also were observed on adult emergence, longevity, reproductive potential, as well as hatchability of eggs. Thus, it is concluded that antibiosis to S. litura could be imparted by artificial inoculation of endophytes and this could be used to develop alternative ecologically safe control strategies.