Chlorpyrifos enrichment enhances tolerance of Anabaena sp. PCC 7119 to dimethoate

Organophosphorus (OP) insecticides are widely used for on-field pest control, constituting about 38% of global pesticide consumption. Insecticide tolerance has been recorded in microorganisms isolated from the contaminated soil. However, the cross-tolerance of laboratory-enriched cultures remains poorly understood. A chlorpyrifos tolerant (T) strain of Anabaena sp. PCC 7119 was developed through continuous enrichment of the wild strain (W). The cross-tolerance of the T strain to the OP insecticide dimethoate was assessed by measuring photosynthetic performance, key enzyme activities and degradation potential. The presence of dimethoate led to a significant reduction in the growth and pigment content of the W strain. In contrast, the T strain demonstrated improved growth and metabolic performance. Chl a and carotenoids were degraded faster than phycobiliproteins in both strains. The T strain exhibited superior photosynthetic performance, metabolic efficiency and photosystem functions, than of W strain, at both the tested dimethoate concentrations (100 and 200 μM). The treated T strain had more or less a normal OJIP fluorescence transient and bioenergetic functions, while the W strain showed a greater fluorescence rise at ≤ 300 μs indicating the inhibition of electron donation to PS II, and at 2 ms due to reduced electron release beyond QA. The T strain had significantly higher levels of esterase and phosphatases, further enhanced by insecticide treatment. Dimethoate degradation efficiency of the T strain was significantly higher than of the W strain. T strain also removed chlorpyrifos more efficiently than W strain at both the tested concentrations. The BCFs of both chlorpyrifos and dimethoate were lower in the T strain compared to the W strain. These findings suggest that the enriched strain exhibits promising results in withstanding dimethoate toxicity and could be explored for its potential as a bioremediating organism for OP degradation.

Distribution and risk assessment of pesticide pollution in small streams adjoining paddy fields

The present investigation was planned to bridge the knowledge gap on spatiotemporal variations of pesticide pollution in small streams adjacent to paddy fields, and to visualize the associated risks in the aquatic ecosystems. We screened 106 pesticides using GCMSMS and LCMSMS from 10 small streams (n = 212, surface water samples) adjacent to paddy fields over seven months. Fifty-five pesticides were detected across different streams and months. The highest mean concentration was detected for fenobucarb (272 ng L-1), followed by thiamethoxam (199 ng L-1). The highest maximum concentration was detected for thiamethoxam ( 13,264 ng L-1), followed by triflumezopyrim ( 11,505 ng L-1). The highest detection frequency was recorded for fenobucarb (80.00%), followed by pretilachlor (79.00%). Out of the ten streams, Attabira stream had the highest mean number of pesticides detected in each sample. Maximum number of pesticides were detected in October followed by September. Pesticides namely, hexaconazole, pretilachlor, tricyclazole, fenobucarb and thiamethoxam were consistently detected across all streams. The risk assessment against the fishes, micro-invertebrates and algae were measured by risk quotient index (RQ). Twenty-five pesticides out of the detected pesticides (n = 55) had risk quotient values greater than 1. The highest RQmax values were observed in case of fenpropathrin followed by cyfluthrin-3. The highest RQmean value was observed in case of cyfluthrin, indicating its higher toxicity to fishes. The present study reveals that small streams are polluted with pesticides and there is a need to develop strategies and policy interventions in regularizing the pesticide uses for reducing the pesticide pollution in aquatic systems.

Volatolomics to Decrypt the Monophagous Nature of a Rice Pest, Scirpophaga Incertulas (Walker)

Scirpophaga incertulas Walker (Lepidoptera: Crambidae, yellow stem borer, YSB) is a monophagous insect pest that causes significant yield loss in rice (Oryza staiva L.). Semiochemical based pest management is being sought as an alternate to chemical pesticides to reduce pesticide footprints. We hypothesized differential release of volatiles from host rice and two companion non-host weeds, Echinochloa colona and Echinochloa crus-galli could be responsible for oviposition and biology of YSB and these chemicals could be used for YSB management. Number of eggs laid, and number of larvae hatched were significantly higher in rice plant as compared to weeds. YSB could only form dead hearts in rice plants. YSB significantly preferred host-plant volatiles compared to the non-host plants both in choice and no-choice tests in an Y-tube olfactometer. 2-Hexenal, hexanal, 2,4-hexadienal, benzaldehyde, nonanal, methyl salicylate and decanal were found in the leaf volatolomes of both the host and non-host plants in HS-SPME-GC-MS (Headspace-Solid phase micro extraction-Gas chromatography-Mass spectrometer). Pentene-3-one, 2-pentyl furan, 2,4-heptadienal, 2-octenal, 2-octenol and menthol were present only in the non-host plants. Fourteen rice unique compounds were also detected. The built-in PCA (Principal Component Analysis) and PLS-DA (Partial least squares-discriminant analysis) analysis in the MS-DIAL tool showed that the volatiles emitted from TN1 formed a cluster distinct from Echinochloa spp. and 2-octenal was identified as a unique compound. Olfactometer bioassays using synthetic compounds showed that rice unique compounds, like xylene, hexanal served as attractants whereas non-host unique compounds, like 2-pentylfuran, 2-octenal acted as repellent. The results indicate that the rice unique compounds xylene, hexanal along with other volatile compounds could be responsible for higher preference of YSB towards rice plants. Similarly, the non-host unique compounds 2-pentylfuran, 2-octenal could possibly be responsible for lower preference and defence against YSB. These compounds could be utilised for devising traps for YSB monitoring and management.

Sublethal phosphine fumigation induces transgenerational hormesis in a factitious host, Corcyra cephalonica

BACKGROUND

The rice moth, Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) is a pest of stored grains and widely used as a factitious host during the mass rearing of several natural enemies of crop pests. Hormesis is well-documented in pest insects, to some extent in natural enemies of pests.

RESULTS

We report transgenerational stimulatory effects of the widely used fumigant, phosphine. The study reports the consequences of sublethal, low lethal and median lethal concentrations (LC5 , LC25 and LC50 ) and untreated control for two sequential generations of the species (G1 to G2 ). In this study, we investigated the life-history traits, nutrient reserves (protein, lipid and carbohydrate) and larval gut microbiome (using 16 s rRNA V3-V4 metagenomics sequencing) of C. cephalonica. Stimulatory effects were observed for various biological traits of C. cephalonica, notably adult longevity, emergence and increased egg hatchability when exposed to LC5 of phosphine. The total protein, lipid and carbohydrate contents of C. cephalonica also were found to be significantly increased by LC5 in both generations. The microbial diversity of LC5 treated larval gut was higher and found to be different from the rest of the treatments. This is the first report showing hormesis to a fumigant insecticide.

CONCLUSION

Our findings increase knowledge on the interaction between hormesis, nutrient reserves and gut bacteria in C. cephalonica exposed to insecticides. Overall, the present study establishes phosphine-induced hormesis at LC5 in the host C. cephalonica, which might help improve the quality of mass rearing of various natural enemies. © 2023 Society of Chemical Industry.

Functional response of an egg parasitoid, Trichogramma chilonis Ishii to sublethal imidacloprid exposure

BACKGROUND

The effectiveness of a biological control agent depends on how well it can control pests and how compatible it is with pesticides. Therefore, we reported the multigenerational effect of a commonly used insecticide, imidacloprid, on the functional response of a widely acclaimed egg parasitoid, Trichogramma chilonis Ishii, to different densities of the host Corcyra cephalonica Stainton eggs. The study investigated the outcomes of the median lethal concentration (LC50 ) and sublethal concentrations (LC5 , LC30 ), along with control treatments for five continuous generations (F1 to F5 ).

RESULTS

The results showed that the F5 generation of LC30 , both of the F1 and F5 generations of LC50 , and the control all had a Type II functional response. A Type I functional response was exhibited for the F1 generation of LC30 and both generations of LC5 . The attack rate on host eggs treated with LC5 and LC30 did not change (decrease) with the shift in the type of functional response as compared to the control. A significant increase in the searching efficiency (a) was observed in the later generation (F5 ) under the exposure of LC5 and LC30 imidacloprid concentrations. A lower handling time (Th ) in both generations of the LC5 followed by LC30 treated individuals was observed when compared with the control and LC50 treatments. The per capita parasitization efficiency (1/Th ) and the rate of parasitization per handling time (a/Th ) were also considerably higher in both the generations of LC5 and LC30 than in the control and LC50 , thereby implying positive effects of imidacloprid on the parasitization potential of T. chilonis.

CONCLUSION

Altogether, these multigenerational outcomes on the functional response of T. chilonis could be leveraged to control the intractable lepidopteran pests under the mild exposure of imidacloprid in integrated pest management (IPM) programs as well as in the mass rearing of the parasitoid, T. chilonis. © 2023 Society of Chemical Industry.

Facile synthesis of novel magnesium oxide nanoparticles for pesticide sorption from water

The quantum of pesticides in surface as well as drinking water has become a serious health hazard. In this experiment, magnesium oxide nanoparticles (MgO NPs) were synthesized using leaves of purple-colored rice variety (Crossa) and utilized for simultaneous removal of three pesticides, namely, thiamethoxam, chlorpyriphos, and fenpropathrin from water. The biogenic MgO NPs were characterized using SEM-EDX, FTIR, XRD, DLS, etc. The optimum synthesis parameters (1 M NaOH, 80 °C, and 2 h) resulted in maximum yield of MgO NPs (87.7 mg), minimum hydrodynamic diameter (35.12 nm), poly dispersity index (0.14) and mean zeta potential (-11 mV). Sorption data of the three pesticides fitted well with non-linear Langmuir and Freundlich isotherm models and non-linear pseudo-second-order kinetic model. The maximum adsorption capacity of MgO NPs for the three pesticides was 87.66 µg/mg, as obtained from the Langmuir isotherm model. Under optimum conditions (initial concentration, 40 mg/L; dose, 30 mg/30 mL; and pH, 9), 60.13, 80.53, and 92.49% removal of thiamethoxam, chlorpyriphos, and fenpropathrin was achieved with a 100% desirability, respectively. Thus, the biogenic MgO NPs could be an efficient adsorbent of pesticides and could be recommended for pesticide decontamination in water treatment plants and domestic water purifier systems.

Phosphine estimation in fumigated food grains using gas chromatography equipped with FPD detector

Phosphine, as per several reports, is considered to be an ideal and effective alternative to methyl bromide (MB) fumigant, phased out globally honouring 'Montreal Protocol'. The food grains fumigated with phosphine are perceived to be residue-free; however, estimation of its residues is imperative. In the present study, the phosphine residues were estimated in grains of wheat, rice, green gram, chickpea and yellow pea fumigated with different formulations of phosphine under 7 and 10 days exposure periods at various locations in India. For efficacy studies, the conventional aluminium phosphide (AlP) tablet (56% @2 and 3 tablet/MT) and granular AlP (77.5% @1.0 and 1.5 g phosphine/m3) formulations were applied. Each treatment including untreated control was replicated thrice. The concentration was monitored every 24 h until the end of exposure periods. Food grain samples were drawn before and post fumigation following a certain waiting period for estimation of phosphine residues using gas chromatography equipped with FPD detector. Residues in fumigated food grains were observed in traces in all the experimental stacks, but below the MRL (0.1 ppm), fixed by Codex Alimentarius Commission (CAC). Phosphine can be considered safe for use as an alternate fumigant in quarantine and long-term storage of food grains leaving residues below MRL.

Development and validation of HS-SPME-GCMS/MS method for quantification of 2-acetyl-1-pyrroline in rice cultivars

The commercial significance of accurate and simple quantification of 2-Acetyl-1-pyrroline (2-AP) cannot be overstated. Present study was carried out to standardize a method for extraction and accurate quantitation of 2-AP from rice grain using GC-MS/MS equipped with HS-SPME auto sampler. The effect of sample quantity, addition of solvent, grinding process, sample particle size, head space parameters and SPME fiber incubation parameters, were optimized in the developed method. Dehusked rice powder (2 g) prepared under liquid nitrogen, and passed through the 80-mesh sieve, incubated for 40 min at 80 °C in headspace, followed by fiber (DVB/Carbon WR/PDMS) saturation time of 15 min, could produce the maximum response. The recovery of 2-AP from fortified sample ranged between 7.02 and 9.02% at 50-200 ng g-1 fortification irrespective of the grain matrices used. Standard addition method was appropriate to overcome the matrix effect and recovery of 2-AP was more than 90% using this method. The developed method was further utilized for quantification of 2-AP in four Basmati and two non-Basmati aromatic rice samples. The content of 2-AP ranged between 57.17 and 147.10 ng g-1 of rice and varied with geographical location. This fully automated method could improve the work efficiency and reduce error during the volatile extraction and adsorption phase.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05674-7.

Residue dynamics and bio-efficacy of triflumezopyrim against Nilaparvata lugens and non-targeted effect on natural enemies in a rice ecosystem

Triflumezopyrim (TMP), a mesoionic insecticide, is commonly used for controlling planthoppers in rice. However, the relationship between the TMP residue and toxicity against brown planthoppers (BPHs) has not been studied in detail. We are reporting the dissipation of TMP from rice plant and soil under field conditions. The median lethal dose and median lethal concentration were 0.036 ng per insect and 0.525 mg L-1, respectively. TMP at recommended dose (25 g a.i. ha-1) recorded 1.25 live BPH per hill as against 25.5 per hill in control at 14 days after treatment. TMP was considered to be harmless to the natural enemies, namely, Cyrtorhinus lividipennis and Lycosa pseudoannulata in the rice ecosystem. The residue of TMP from rice plant and soil was estimated using the QuEChERS method using three different doses (12.5, 25, and 50 g a.i. ha-1). The limit of quantitation (LOQ) of TMP in plant and soil was 5 µg kg-1 and 1 µg kg-1, respectively. The maximum content of TMP in soil was less than 1% that of plant content on day 1. The dissipation pattern of TMP both from plant and soil was better explained by the first-order double-exponential decay model (FODED) as compared to the first-order kinetic model. Overall, the half-lives of TMP were ranged from 2.21 to 3.02 days in plant tissues and 3.78 to 4.79 days in soil as per the FODED model. Based on the persistence and toxicity of TMP, we could conclude that TMP will be effective against BPH up to 7-10 days after application. Triflumezopyrim with reasonable persistence and high efficacy could be recommended as an alternate pesticide in BPH management in rice.

Performance of Trichogramma japonicum under field conditions as a function of the factitious host species used for mass rearing

Different factitious hosts were used to mass rear Trichogramma japonicum Ashmead in different parts of the globe because thorough details were lacking in both the laboratory and the field. The objective of this study was to compare, parasitoid, T. japonicum reared in different factitious hosts. Three commonly used factitious host eggs, Corcyra cephalonica (Stainton), Ephestia kuehniella Zeller and Sitotroga cerealella Olivier were tested under laboratory conditions and then in the field over a yellow stem borer, Scirpophaga incertulus (Walker) of rice. The highest parasitism by T. japonicum was observed on E. kuehniella eggs. The parasitoid’s highest emergence (88.99%) was observed on S. cerealella eggs at 24 h exposure, whereas at 48 h it was on E. kuehniella eggs (94.66%). Trichogramma japonicum females that emerged from E. kuehniella eggs were significantly long-lived. The days of oviposition by hosts and the host species were significant individually, but not their interaction. Higher proportions of flying T. japonicum were observed when reared on E. kuehniella and C. cephalonica eggs. Field results showed that T. japonicum mass-reared on E. kuehniella showed higher parasitism of its natural host, S. incertulus eggs. Hence, by considering these biological characteristics and field results, E. kuehniella could be leveraged for the mass rearing of quality parasitoids of T. japonicum in India, the Asian continent and beyond.

Trichoderma-mediated rice straw compost promotes plant growth and imparts stress tolerance

Rice straw burning is causing huge economic losses and environmental hazards. Microbial mediated ex situ composting could be a viable solution which would not only reduce the straw burning but also will enrich nutrition to the soil. Strains of Trichoderma isolated from tree bark were tested to decompose rice straw efficiently, and the Trichoderma-mediated rice straw compost was used subsequently to improve rice growth. Two isolates of Trichoderma reesei (NRRIT-26 and NRRIT-27) decomposed the straw by producing higher decomposing enzymes, like total cellulase (≥ 1.87 IU mL-1), endoglucanase (≥ 0.75 IU mL-1), xylanase (≥ 163.49 nkat mL-1), and laccase (≥ 11.75 IU mL-1). Trichoderma decomposed rice straw compost had higher nutrient contents (1.97% N, 2.04% K, and 0.88% P) and optimum C/N ratio (28:2) as compared to control. The Trichoderma decomposed rice straw as a nutrient reduced the mean germination time (2.2 days as compared to 4 days in control) and enhanced the seedling vigor and total chlorophyll content in rice. Expression of defense enzymes, like catalase (≥ 200% both in shoot and root), peroxidase (≥ 180% in root and ≥ 300% in shoot), and superoxide dismutase (≥ 160% in root and ≥ 90% in shoot), were higher in treated plants as compared to control indicating higher stress tolerance ability to crops. We conclude that the Trichoderma-mediated rice straw management is a viable option and has the potential to reduce straw burning, and at the same time, the compost could enrich soil fertility and impart intrinsic stress tolerance to rice.

Seed Biopriming With Trichoderma Strains Isolated From Tree Bark Improves Plant Growth, Antioxidative Defense System in Rice and Enhance Straw Degradation Capacity

This study is a unique report of the utilization of Trichoderma strains collected from even tree barks for rice plant growth, its health management, and paddy straw degradation. Seven different spp. of Trichoderma were characterized according to morphological and molecular tools. Two of the isolated strains, namely Trichoderma hebeiensis and Trichoderma erinaceum, outperformed the other strains. Both of the strains controlled four important rice pathogens, i.e., Rhizoctonia solani (100%), Sclerotium oryzae (84.17%), Sclerotium rolfsii (66.67%), and Sclerotium delphinii (76.25%). Seed bio-priming with respective Trichoderma strains reduced the mean germination time, enhanced the seedling vigor and total chlorophyll content which could be related to the higher yield observed in two rice varieties; Annapurna and Satabdi. All the seven strains accelerated the decomposition of rice straw by producing higher straw degrading enzymes like total cellulase (0.97–2.59 IU/mL), endoglucanase (0.53–0.75 IU/mL), xylanase (145.35–201.35 nkat/mL), and laccase (2.48–12.60 IU/mL). They also produced higher quantities of indole acetic acid (19.19–46.28 μg/mL), soluble phosphate (297.49–435.42 μg/mL), and prussic acid (0.01–0.37 μg/mL) which are responsible for plant growth promotion and the inhibition of rice pathogen populations. Higher expression of defense enzymes like catalase (≥250% both in shoot and root), peroxidase (≥150% in root and ≥100% in shoot), superoxide dismutase (≥ 150% in root and ≥100% in shoot), polyphenol oxidase (≥160% in shoot and ≥120% in shoot), and total phenolics (≥200% in root and ≥250% in shoot) as compared to the control indicates stress tolerance ability to rice crop. The expression of the aforementioned enzymes were confirmed by the expression of corresponding defense genes like PAL (>3-fold), DEFENSIN (>1-fold), POX (>1.5-fold), LOX (>1-fold), and PR-3 (>2-fold) as compared to the non-treated control plants. This investigation demonstrates that Trichoderma strains obtained from tree bark could be considered to be utilized for the sustainable health management of rice crop.

Green silver nano-particles: synthesis using rice leaf extract, characterization, efficacy, and non-target effects

Green synthesis of silver nano-particles (AgNPs) from silver nitrate was carried out using purple-colored rice leaves' extracts containing higher phenols, anthocyanins, and flavonoids. The efficacy of synthesized AgNPs was tested against rice diseases and investigation was carried out to check negative effect of AgNPs on soil microbes. Substantial reduction of total anthocyanins, total phenols, and total flavonoids was observed in reaction mixture during AgNP formation indicating the role of secondary metabolites on AgNP formation and stabilization. Scanning electron microscopy coupled with energy-dispersive spectroscopic images and FTIR spectral analysis of AgNPs confirmed the presence of elemental silver encapped by biomolecules. The optimized reaction parameters for synthesis of AgNPs from silver nitrate were (a) 48 h of incubation, (b) 9:1 (v/v) 1 mM AgNO3:plant extract, and (c) room temperature at 20-30 °C. Zeta potential and hydrodynamic particle sizes of synthesized AgNPs were ranged between - 16.61 to - 29.45 mV and 36-107 nm, respectively, at different time of incubation. AgNPs could control effectively Rhizoctonia solani and Xanthomonas oryzae pv. Oryzae and Helminthosporium oryzae. AgNPs at higher concentration could cause negative effect on microbial biomass carbon and soil enzymes for distant future. But the negative effects of AgNP solution (10% of 1 mM AgNPs) were comparable to commercial fungicide, carbendazim. The synthesized AgNPs with desirable characters were effective against a number of disease-causing pathogens in rice, and it can be recommended as broad-spectrum pesticide.

Role of climate change variables (standing water and rainfall) on dissipation of chlorantraniliprole from a simulated rice ecosystem

Chlorantraniliprole (CAP) is extensively used for rice pest management. Lack of information on the role of standing water and amount and timing of rainfall on CAP dissipation in rice ecosystem could hamper its prospective use. Present study was performed to investigate the effects of different water regimes (saturated, 5 and 10 cm standing water) and simulated rainfall (40 and 100 mm occurred at 4, 8 and 24 h after CAP application) on leaching, surface runoff and dissipation of CAP into components of rice ecosystem. The results showed highest concentration of CAP residues in soil and plant under saturated condition followed by 5 and 10 cm standing water conditions. Whereas, the highest concentration of CAP in leachates was detected under 10 cm standing water (12.19 ng mL^-1). The results revealed large amount of leaching (21.99 ng mL^-1) and surface runoff (42.25 ng mL^-1) losses of CAP when 100 mm rainfall occurred at 4 h after pesticide application. The total quantity of CAP residues in soil and plant was highest when rainfall occurred at 24 h after pesticide application under both the rainfall amounts. Water stagnation and high intensity rainfall occurred shortly after pesticide application will contribute to pesticide loss to non-target sites through surface run-off and leaching. There will be less pesticide available in soil for plant uptake which may not be sufficient to kill the target organisms.

Indigenous biobed to limit point source pollution of imidacloprid in tropical countries

Point pollution of pesticides originating from the washing of spraying machines could be controlled by biobed system and it is in use in temperate countries. The biobed system is yet to be established in tropical countries. An indigenous biobed system was prepared using local resources like rice straw, farm yard manures (FYM) and paddy field soil to suit the tropical climate. Lowermost 3 cm layer of the biobed system was filled with rice husk biochar to prevent leaching of pesticides from the system. This model system was tested with high doses of imidacloprid (178 mg/column), a commonly used pesticide against number of insect-pests in different crops, for its degradation. The bio-mix trapped a major part of the imidacloprid on the top most layer of the biobed column and only a very small part of imidacloprid recovered from the leachate. The biobed system could degrade 70.13% of applied imidacloprid within 15 days of the experiment and only 5.27% of the total pesticide recovered 90 days after incubation. Addition of biochar layer adsorbed imidacloprid from the outgoing leachate from the biobed column. Biomixture boosted microbial activity more particularly fungal population, which might be responsible for imidacloprid degradation. Microbial biomass carbon, and soil enzymes indicated faster dissipation of imidacloprid from the top layer of the biobed. This simple but efficient biobed system using local resources can fulfill the need of the small and marginal farmers of Asian countries for pesticide decontamination.

Non-target effect of bispyribac sodium on soil microbial community in paddy soil

Bispyribac sodium is frequently used herbicide in the rice field. Though, it has been targeted to kill rice weeds, but its non-target effect on soil microbes in paddy soil was largely unknown. Therefore, in the present study, an attempt was made to assess the non-target effect of bispyribac sodium on alteration of functional variation of soil microbial community and their correlation with microbial biomass carbon (MBC) and soil enzymes. A microcosm experiment set up was made comprising three treatments viz., control (CON) (without application of bispyribac sodium), recommended dose of bispyribac sodium (35 g ha^-1) (BS), and double the dose of BS (70 g ha^-1) (DBS). Results indicated that the MBC and soil enzyme activities (dehydrogenase, alkaline phosphatase and urease) in BS and DBS-treated soil were significantly (p < 0.05) declined from 1^st to 30^th day after application as compared to CON. Counts of heterotrophic bacteria, actinomycetes and fungal population were also decreased in BS and DBS-treated soil. The average well color development (AWCD) values derived from Biolog®ecoplates followed the order of DBS ˂ BS ˂ CON. Shannon index value was high (p ≤ 0.05) in CON compared to soil-treated with BS and DBS. Principal component analysis (PCA) showed a clear distinction of the cluster of treatments between CON, BS and DBS. Biplot analysis and heatmap suggested that carboxylic compounds and amino acids showed positive response towards BS-treated soil, whereas phenolic compounds had positive correlation with DBS-treated soil. PCA analysis indicated that oligotrophs was rich in BS-treated paddy soil, whereas copiotrophs and asymbiotic nitrogen fixers were richer in DBS treatment. Overall, the present study revealed that application of recommended dose of BS and its double dose alter the soil microbial population, enzyme activities and functional microbial diversity in paddy soil.

Deciphering the associated risk on soil microbes upon use of biopesticides in rice ecosystem

Plant species, viz Cleistanthus collinus, Lantana camara, and Strychnos nux-vomica are being traditionally used for pest management in rice. However, limited investigation has been carried out to understand the toxic effect of these materials on soil microbes. Hot water extracts of these plants were evaluated for their effects on soil microbial population and enzyme activities along with neem oil and chlorpyrifos as check. Soil microbial population, viz bacteria, fungi, phosphate-solubilizing bacteria (PSB), and asymbiotic nitrogen fixers were unchanged after application of plant extracts. Maximum population of bacteria including PSB and asymbiotic nitrogen fixers were observed in control, whereas, S. nux-vomica, and C. collinus-treated soil had higher number of actinomycetes and fungal population, respectively. Soil microbial biomass did not vary differently among the plant extracts. Application of plant extracts did not alter dehydrogenase, β-glycosidase, acid phosphatase, alkaline phosphatase, and urease content in soil. Secondary metabolites present in these plant extracts may be responsible for variable effects on soil microbes. Chlorpyrifos had a fleeting negative effect on soil microbes and enzymes in comparison to plant extracts. All the three plants did not have any negative effect on soil microbes and enzymes and can be safely recommended in rice pest management.

Dissipation of chlorantraniliprole in contrasting soils and its effect on soil microbes and enzymes

An experiment was set up to determine the rate of dissipation of chlorantraniliprole (CTP) from two soils with contrasting properties. The other objective of the study was to find out the effect of CTP on soil microorganisms (population, microbial biomass carbon and soil enzymes) under controlled environment. CTP residues when applied at recommended dose ((RD) (at 40 g a.i./ha)) could not be recovered either from alluvial soil or red soil at 60 days post application of CTP in a microcosm study. Higher clay content led to higher half-life in alluvial soil compared to red soil. CTP could not be recovered from RD treatment at 30 days after pesticide application under controlled environment. Faster dissipation of CTP was observed in rice rhizosphere soil with 23.89 and 34.65 days dissipation half-lives for RD and double the recommended dose (DRD) treatments, respectively. Different doses of chlorantraniliprole did not have considerable negative effect on actinomycetes, fungi, biological nitrogen fixers and phospahte solubilising bacteria except the bacteria population. Among the treatments, DRD recorded the lowest activity of dehyrodeganse, fluoresein diacetate hydrolase, acid and alkaline phosphatases followed by RD treatment. Microbial biomass carbon, β -glycosidase and urease did not vary significantly among the different doses of CTP. In general, RD did not have negative effcts on soil microbes. Hence, CTP can be recommeded in rice pest managment maintaining existing soil microbes and soil enzymes activity.

Candidate screening of blast resistance donors for rice breeding

Rice blast is one of the most serious diseases in the world. The use of resistant cultivars is the most preferred means to control this disease. Resistance often breaks down due to emergence of new races; hence identification of novel resistance donors is indispensable. In this study, a panel of 80 released varieties from National Rice Research Institute, Cuttack was genotyped with 36 molecular markers that were linked to 36 different blast resistance genes, to investigate the varietal genetic diversity and molecular marker-trait association with blast resistance. The polymorphism information content of 36 loci varied from 0.11 to 0.37 with an average of 0.34. The cluster analysis and population structure categorized the 80 National Rice Research Institute released varieties (NRVs) into three major genetic groups. The principal co-ordinate analysis displays the distribution of resistant and moderately resistant NRVs into different groups. Analysis of molecular variance result demonstrated maximum (97%) diversity within populations and minimum (3%) diversity between populations. Among tested markers, two markers (RM7364 and pi21_79-3) corresponding to the blast resistance genes (Pi56(t) and pi21) were significantly associated and explained a phenotypic variance of 4.9 to 5.1% with the blast resistance. These associated genes could be introgressed through marker-assisted to develop durable blast resistant rice varieties. The selected resistant NRVs could be good donors for the blast resistance in rice crop improvement research.

Mechanism of plant mediated methane emission in tropical lowland rice

Methane (CH₄) is predominantly produced in lowland rice soil, but its emission from soil to atmosphere primarily depends on passage/conduit or capillary pore spaces present in rice plants. The gas transport mechanism through aerenchyma pore spaces of rice cultivars was studied to explore the plant mediated CH₄ emission. Seven rice cultivars, based on the life cycle duration (LCD), were tested in tropical eastern India. Three LCD groups were, (a) Kalinga 1 and CR Dhan 204 (LCD: 110-120 days); (b) Lalat, Pooja and CR 1014 (LCD: 130-150 days); and (c) Durga and Varshadhan (LCD: 160-170 days). Rate of CH₄emission, root exudates, root oxidase activities and shoot aerenchyma pore spaces were analyzed to study the mechanism of plant mediated emission from rice. Aerenchyma pore space was quantified in the hypothesis that it regulates the CH₄ transportation from soil to atmosphere. The ratio of pore space area to total space was lowest in Kalinga 1 cultivar (0.29) and highest was in Varshadhan (0.43). Significant variations in the methane emission were observed among the cultivars with an average emission rate ranged from 0.86 mg m^-2 h^-1 to 4.96 mg m^-2 h^-1. The CH4 emission rates were lowest in short duration cultivars followed by medium and long duration ones. The greenhouse gas intensity considering average CH₄ emission rate per unit grain yield was also lowest (0.35) in Kalinga 1 and relatively less in short and medium duration cultivars. Root exudation was higher at panicle initiation (PI) than maximum tillering (MT) stage. Lowest exudation was noticed in (197.2 mg C plant^-1 day^-1) Kalinga 1 and highest in Varsadhan (231.7 mg C plant^-1 day^-1). So we can say, the rate of CH₄ emission was controlled by aerenchyma orientation, root exudation and biomass production rate which are the key specific traits of a cultivar. Identified traits were closely associated with duration and adaptability to cultivars grown in specific ecology. Therefore, there is possibility to breed rice cultivars depending on ecology, duration and having less CH₄ emission potential, which could be effectively used in greenhouse gas mitigation strategies.

Blast resistance in Indian rice landraces: Genetic dissection by gene specific markers

Understanding of genetic diversity is important to explore existing gene in any crop breeding program. Most of the diversity preserved in the landraces which are well–known reservoirs of important traits for biotic and abiotic stresses. In the present study, the genetic diversity at twenty-four most significant blast resistance gene loci using twenty-eight gene specific markers were investigated in landraces originated from nine diverse rice ecologies of India. Based on phenotypic evaluation, landraces were classified into three distinct groups: highly resistant (21), moderately resistant (70) and susceptible (70). The landraces harbour a range of five to nineteen genes representing blast resistance allele with the frequency varied from 4.96% to 100%. The cluster analysis grouped entire 161 landraces into two major groups. Population structure along with other parameters was also analyzed to understand the evolution of blast resistance gene in rice. The population structure analysis and principal coordinate analysis classified the landraces into two sub–populations. Analysis of molecular variance showed maximum (93%) diversity within the population and least (7%) between populations. Five markers viz; K3957, Pikh, Pi2–i, RM212and RM302 were strongly associated with blast disease with the phenotypic variance of 1.4% to 7.6%. These resistant landraces will serve as a valuable genetic resource for future genomic studies, host–pathogen interaction, identification of novel R genes and rice improvement strategies.

Toxicological effect of underutilized plant, Cleistanthus collinus leaf extracts against two major stored grain pests, the rice weevil, Sitophilus oryzae and red flour beetle, Tribolium castaneum

Toxicity and repellency activity of Cleistanthus collinus (Roxb.) (CC) leaf extracts were evaluated against rice weevil, Sitophilus oryzae (L.) and red flour beetle, Tribolium castaneum (Herbst) under laboratory condition. Five concentration(s) (1%, 1.5%, 2%, 2.5% and 4%) with two controls (acetone and water) treatments along with deltamethrin were used for direct and contact residual toxicity. The insect that survived after CC exposure were transferred to an untreated feeding substrate and the population buildup of subsequent two generation were recorded after 30 (F₁) and 60 days (F₂). In the contact residual toxicity, highest CC concentration (4%) produced 75% mortality in S. oryzae and 62.5% mortality in T. castaneum during 7 days of exposure, whereas in direct toxicity the mortality were 81% and 58% respectively, for S. oryzae and T. castaneum. The long term effect of CC was apparent in both the insect species, where F₂ populations were significantly decreased in the CC treatments. CC treatment at 4% produced similar adult mortality in comparison to deltamethrin at 1%. In addition, repellent activity of CC extracts was observed against both S. oryzae and T. castaneum. This is the first step towards assessing the scientific basis for the understanding the effectiveness of CC extracts against stored grain pests and it could be a viable eco-friendly option for stored grain insect pest management.

Imidacloprid application changes microbial dynamics and enzymes in rice soil

Extensive use of imidacloprid in rice ecosystem may alter dynamics of microorganisms and can change soil biochemical properties. The objective of this study was to assess the effect of imidacloprid on growth and activities of microbes in tropical rice soil ecosystem. Four treatments, namely, recommended dose (at 25g a.i. ha^-1, RD), double the recommended dose (at 50g a.i. ha^-1, 2RD), five times the recommended dose (at 125g a.i. ha^-1, 5RD) & ten times the recommended dose (at 250g a.i. ha^-1, 10RD) along with control were imposed under controlled condition. Dissipation half lives of imidacloprid in soil were 19.25, 20.38, 21.65 and 33.00 days for RD, 2RD, 5RD and 10RD, respectively. In general bacteria, actinomycetes, fungi and phosphate solubilising bacteria population were disturbed due to imidacloprid application. Changes in diversity indices within bacterial community confirmed that imidacloprid application significantly affected distribution of bacteria. Total soil microbial biomass carbon content was reduced on imidacloprid application. Except dehydrogenase and alkaline phosphatase activities, all other soil enzymes namely, β-glycosidase, fluorescien diacetate hydrolase, acid phosphatase and urease responded negatively to imidacloprid application. The extent of negative effect of imidacloprid depends on dose and exposure time. This study concludes imidacloprid application had transient negative effects on soil microbes.

Effect of Abiotic Factors on Degradation of Imidacloprid

The role of soil moisture, light and pH on imidacloprid dissipation was investigated. A high performance liquid chromatography (HPLC) based method was developed to quantify imidacloprid present in soil with a recovery of more than 82%. Rate of dissipation of imidacloprid from soil was faster in submerged condition compared to field capacity and air dried condition. Imidacloprid dissipated non-significantly between sterile and non-sterile soils, but at field capacity, the dissipation was faster in non-sterile soil compared to sterile soil after 60 days of incubation. Similarly, under submergence, the dissipation of imidacloprid was 66.2% and 79.8% of the initial in sterile and non-sterile soils, respectively. Imidacloprid was rather stable in acidic and neutral water but was prone to photo-degradation. Therefore, imidacloprid degradation will be faster under direct sunlight and at higher soil moisture.

Effect of Pretilachlor on Soil Enzyme Activities in Tropical Rice Soil

Pretilachlor treatments, namely, recommended dose at 600 g a.i. ha^-1 (RD), double the recommended dose at 1200 g a.i. ha^-1 (2RD), ten times of the recommended dose at 6000 g a.i. ha^-1 (10RD) along with control, were used to study the effects of pretilachlor on soil enzymes in tropical rice soil. Pretilachlor, at recommended dose completely dissipated 30 days after herbicide application. Twenty days after herbicide application, the dehydrogenase activity was inhibited up to 27 %, 28 % and 40 % of initial values of RD, 2RD and 10RD treatments, respectively. Increase in fluorescein diacetate hydrolase activity was observed during the first 25 days post herbicide application up to 29 %, 36 % and 10 % of initial values of RD, 2RD and 10RD treatments, respectively. β-Glucosidase activity in the experiment did not provide a specific trend. In general, urease and acid phosphatase activities were not influenced by pretilachlor application. There were significant differences in alkaline phosphatase activities among the treatments until 25 days after herbicide application. Hence, pretilachlor may cause short term transitory changes in soil enzyme parameters. However, it has negative impact on soil enzymes at very high dose.

Non-target effect of continuous application of chlorpyrifos on soil microbes, nematodes and its persistence under sub-humid tropical rice-rice cropping system

Application of pesticide in agricultural fields is "unnecessary evil" for non-target microflora and fauna. Hence, to identify the safer pesticide molecules against non-target microbes, a long-term pesticide experiment was initiated at National Rice Research Institute, Cuttack, India. In the present study, the effect of continuous application of chlorpyrifos (0.5kgha^-1) in rice fields on non-target groups of soil microbes and nematodes was studied for seven seasons (four wet and three dry seasons) during 2009-2013. Treatments were arranged in a randomized complete block design with four replications of chlorpyrifos-treated (0.5kg a.i. ha^-1) (CT) and untreated control (UT) plots. During seven seasons of experimentation, regular application of chlorpyrifos had no significant effect on population of heterotrophic aerobic, anaerobic, oligotrophic and copiotrophic bacteria in CT compared to UT, whereas, population of asymbiotic aerobic nitrogen fixer, nitrifiers, denitrifiers, gram positive and spore-forming bacteria were significantly reduced by nearly 0.25-2 fold in CT than UT. However, comparatively less deviation in population of actinomycetes, fungi, phosphate solubilizing and sulfur oxidizing bacteria were observed in CT than UT. Significant interactions were found between effects of chlorpyrifos with time in population dynamics of microbes. In plant parasitic nematode species, Meloidogyne graminicola (RRKN) and Hirschmanniella spp. (RRN), were significantly lower (p<0.01) in CT compared to UT after first year onwards. The overall observation of five years data indicated that the RRKN population showed a decreasing trend (R²=0.644) whereas RRN showed increasing trend (R²=0.932) in CT. The drastic chlorpyrifos dissipation was noticed after 15 days of application from the initial residue of 0.25mgkg^-1 soil, which indicated that chlorpyrifos residue in rice field soil was not persistent and its half-life was found to be 4.02 days. Overall, the present findings revealed that non-target effect of repetitive application of chloropyrifos (0.5kgha^-1) on soil microbes and nematodes was found less under rice-rice cropping system.

Humid thermal ratio as a tool to assess mango thrips dynamics under subtropical climatic condition

Weather factors play an important role in occurrence of thrips on mango. Keeping this in view, the present investigation was set out to assess the thrips population dynamics using humid thermal index, based on data sets from 22 fixed plot mango orchards in and around Lucknow. Results revealed that the highest thrips population of 3.36/panicle was recorded in Kakori (Fixed plot -I) orchard, which was followed by 2.4 and 2.06 at CISH III block and Kanar (Fixed II) respectively during the year 2013, whereas corresponding values were 4.05, 3.08 and 2.50 at CISH Block III, CISH Bolck II and Allupur respectively during 2014. The frequency distribution explained that the thrips population of <2 /panicle was widely distributed with highest frequency level. The humid thermal ratio ranged from 1.44 to 2.27 and 1.20 to 2.34 during 2013 and 2014 respectively across standard meteorological weeks. The peak thrips incidence was 6.18 /panicle during 2013 and 4.67/panicle during 2014, the corresponding values of humid thermal ratio were 1.47 and 2.05 respectively. The positive correlation was found between humid thermal ratio and thrips population dynamics during 2013 (r = 0.52**) and 2014 (r = 0.72**). Pooled data showed significant and positive correlation between humid thermal ratio and thrips population. Pooled analysis had explained up to 94 per cent of variation with exponential model (Thrips population = 0.007e2.778HTR, R2 = 0.94**) and suggested that this index might be used in understanding the mango thrips population dynamics under subtropical environmental condition.

Role of nano-range amphiphilic polymers in seed quality enhancement of soybean and imidacloprid retention capacity on seed coatings

BACKGROUND

Nano-size and wide-range solubility of amphiphilic polymers (having both hydrophilic and hydrophobic blocks) can improve uniformity in seed coatings. An investigation was carried out to assess the positive effect of amphiphilic polymers over hydrophilic or hydrophobic polymers as seed coating agents and pesticide carriers.

RESULTS

Amphiphilic polymers with 127.5-354 nm micelle size were synthesized in the laboratory using polyethylene glycols and aliphatic di-acids. After 6 months of storage, germination of uncoated soybean seeds decreased drastically from 97.80 to 81.55%, while polymer-coated seeds showed 89.44-95.92% germination. Similarly, vigour index-1 was reduced from 3841.10 to 2813.06 for control seeds but ranged from 3375.59 to 3844.60 for polymer-coated seeds after 6 months. The developed imidacloprid formulations retained more pesticide on soybean seed coatings than did a commercial formulation (Gaucho(®) 600 FS). The time taken for 50% release of imidacloprid from seed coatings in water was 7.12-9.11 h for the developed formulations and 0.41 h for the commercial formulation.

CONCLUSION

Nano-range amphiphilic polymers can be used to protect soybean seeds from ageing. Formulations as seed treatments may produce improved and sustained efficacy with minimum environmental contamination. © 2016 Society of Chemical Industry.

Dissipation kinetics of spinosad from tomato under sub-tropical agro-climatic conditions

The dissipation of spinosad in/on tomato and soil was studied at Indian Agricultural Research Institute, New Delhi, under field condition. The optimized sample preparation technique using high performance liquid chromatography (HPLC) with UV detector gave the limit of quantification (LOQ) of 0.05 μg g(-1) of tomato. Spinosad residues were below the determination limit in/on tomato fruits after 15 days of application for recommended dose (51 g a.i. ha(-1)). The half-life of spinosad was in between 3.18 to 3.74 days for the recommended dose. Similarly half-life of 4.14 to 4.71 days was observed for double the recommended dose. The study also investigated the persistence of spinosad in soil and it has been found that half-life of spinosad in soil was 5.49 to 6.36 days for the recommended dose and 6.76 to 6.91 days for double the recommended dose. Based on the CODEX-MRL of spinosad (0.3 mg kg(-1)), pre-harvest interval (PHI) was 7.54 days for the recommended dose of spray.

Non-target effects of pretilachlor on microbial properties in tropical rice soil

The use of herbicides has been questioned in recent past for their non-target effects. Therefore, we planned to study the effect of pretilachlor on growth and activities of microbes in tropical rice soil under controlled condition at National Rice Research Institute, Cuttack, India. Three pretilachlor treatments, namely, recommended dose at 600 g a.i. ha(-1) (RD), double the recommended dose at 1200 g a.i. ha(-1) (2RD), and ten times of the recommended dose at 6000 g a.i. ha(-1) (10RD) along with control, were imposed. The initial residue (after 2 h of spray) deposits in soil were 0.174, 0.968, and 3.35 μg g(-1) for recommended, double the recommended, and ten times of the recommended doses, respectively. No residue in soil was detected in RD treatment on day 45. The half life values were 16.90, 17.76, and 36.47 days for RD, 2RD, and 10RD treatments, respectively. Application of pretilachlor at 10RD, in general, had significantly reduced the number of bacteria, actinomycetes, fungi, nitrogen fixers, and microbial biomass carbon. Pretilachlor at RD did not record any significant changes in microbial properties compared to control. The results of the present study thus indicated that pretilachlor at RD can be safely used for controlling grassy weeds in rice fields.

Effect of elevated CO2 on chlorpyriphos degradation and soil microbial activities in tropical rice soil

Impact of elevated CO2 on chlorpyriphos degradation, microbial biomass carbon, and enzymatic activities in rice soil was investigated. Rice (variety Naveen, Indica type) was grown under four conditions, namely, chambered control, elevated CO2 (550 ppm), elevated CO2 (700 ppm) in open-top chambers and open field. Chlorpyriphos was sprayed at 500 g a.i. ha(-1) at maximum tillering stage. Chlorpyriphos degraded rapidly from rice soils, and 88.4% of initially applied chlorpyriphos was lost from the rice soil maintained under elevated CO2 (700 ppm) by day 5 of spray, whereas the loss was 80.7% from open field rice soil. Half-life values of chlorpyriphos under different conditions ranged from 2.4 to 1.7 days with minimum half-life recorded with two elevated CO2 treatments. Increased CO2 concentration led to increase in temperature (1.2 to 1.8 °C) that played a critical role in chlorpyriphos persistence. Microbial biomass carbon and soil enzymatic activities specifically, dehydrogenase, fluorescien diacetate hydrolase, urease, acid phosphatase, and alkaline phosphatase responded positively to elevated CO2 concentrations. Generally, the enzyme activities were highly correlated with each other. Irrespective of the level of CO2, short-term negative influence of chlorpyriphos was observed on soil enzymes till day 7 of spray. Knowledge obtained from this study highlights that the elevated CO2 may negatively influence persistence of pesticide but will have positive effects on soil enzyme activities.

Investigating Role of Abiotic Factors on Spinosad Dissipation

The effect of abiotic factors on dissipation of spinosad (soil moisture regimes, pH, and light) was studied. Spinosad residues were estimated using high performance liquid chromatography fitted with a UV detector. Under laboratory conditions, half-lives of spinosad were 9.0 and 7.7 days for air dried and field capacity soils, respectively. Percent dissipation of spinosad after 30 days was 47.02, 22.35, 62.5, 68.23 and 76.47 in solution with an aqueous pH of 10.85, 9.15, 6.97, 3.90 and 2.04, respectively. The half-life of spinosad in UV and sunlight was only 1.6 and 5.2 h, respectively. Light, especially the UV component, is an important factor for degradation of spinosad compared to other abiotic conditions.

Gut microbes influence fitness and malaria transmission potential of Asian malaria vector Anopheles stephensi

The midgut of parasite transmitting vector, Anopheles stephensi is a physiologically dynamic ecological niche of resident microbes. The gut resident microbes of anisomorphic and physiologically variable male and female A. stephensi mosquitoes were different (Rani et al., 2009). To understand the possible interaction of gut microbes and mosquito host, we examined the contribution of the microbe community on the fitness of the adult mosquitoes and their ability to permit development of the malaria parasite. A. stephensi mosquitoes were fed with antibiotic to sterilize their gut to study longevity, blood meal digestion, egg laying and maturation capacity, and consequently ability to support malaria parasite development. The sterilization of gut imparted reduction in longevity by a median of 5 days in male and 2 days in female mosquitoes. Similarly, the sterilization also diminished the reproductive potential probably due to increased rate of the resorption of follicles in ovaries coupled with abated blood meal digestion in gut-sterilized females. Additionally, gut sterilization also led to increased susceptibility to oocyst development upon feeding on malaria infected blood. The susceptibility to malaria parasite introduced upon gut sterilization of A. stephensi was restored completely upon re-colonization of gut by native microbes. The information provided in the study provides insights into the role of the gut-resident microbial community in various life events of the mosquito that may be used to develop alternate malaria control strategies, such as paratransgenesis.

Malaria among the Jarawas, a primitive and isolated tribe on the Andaman islands, India

The Jarawas are a primitive Negrito tribe of the Andaman islands, India. The members of this tribe have been geographically and socially isolated from the other inhabitants of the islands. None had attended a hospital or health unit until 1997, when a Jarawa boy with a fractured leg was taken to a hospital in Port Blair, and successfully treated. Since then, increasing numbers of Jarawas have sought treatment at the hospital and/or begun to make other contact with non-Jarawas on the islands. No malaria had ever been reported in the tribe until 2001, when an outbreak of febrile illness triggered a malariological survey. Malarial parasites, all identified microscopically as Plasmodium falciparum, were detected in the bloodsmears of 30 of the 179 Jarawas investigated. Although most malaria among the non-Jarawa inhabitants of the islands is caused by P. vivax, only P. falciparum was detected when blood samples from 26 of the subjects were investigated in PCR-based assays. Genetic-diversity studies, based on the msp(1) and msp(2) polymorphic markers, also revealed a relatively low level of polymorphism in the P. falciparum parasites infecting the Jarawas, compared with that seen in other areas of India. It seems possible that malarial parasites have only recently reached the Jarawas, as the result of the weakening of the tribe's isolation from other humans on the Andaman islands.

Comparative susceptibilities of species T and U of the Anopheles fluviatilis complex to Plasmodium vinckei petteri sporogony

Anopheles fluviatilis James is an important malaria vector in Indian subcontinent. An. fluviatilis exists as a complex of three sibling species, of which two species, T and U, have been colonized so far. Attempts were made to study the comparative susceptibility of species T and U of the An. fluviatilis complex to rodent malaria parasite Plasmodium vinckei petteri by using Anopheles stephensi Liston as calibrator for variable infectivity in different isolates. An. stephensi, which was used as control, became readily infected, with 60-65% mosquitoes carrying developing oocysts, whereas in species T and species U, approximately 50 and 63%, respectively, of mosquitoes carried oocyts. An. fluviatilis species T was found comparatively less susceptible to P. v. petteri sporogonic development compared with species U. Moreover, significantly lesser sporozoites rate (11%) was observed in species T compared with 31% in species U. Species T and species U are not considered as malaria vectors in India in the field. However, in the laboratory, both these species are able to support the malaria sporogony.

Genetic diversity in merozoite surface protein-1 and 2 among Plasmodium falciparum isolates from malarious districts of tribal dominant state of Jharkhand, India

INTRODUCTION

The genetic make-up of malaria parasite is potent for understanding the parasite virulence, designing antimalarial vaccine and evaluating the impact of malaria control measures. There is a paucity of information on genetic structure of Plasmodium falciparum in Jharkhand, India where malaria is rampant and this study aimed to establish molecular characterization of P. falciparum field isolates from Jharkhand measured with two highly polymorphic genetic markers, i.e. the merozoite surface proteins (MSPs) 1 and 2.

METHODS

The genetic diversity of P. falciparum population from low transmission area, Ranchi, Bokaro and Hazaribagh and highly malarious area, Latehar and Palamau districts of Jharkhand were evaluated by polymerase chain reaction-sequencing analyzing msp-1 and msp-2 genes to explore the genetic structure of parasite from this understudied region.

RESULTS

A total of 134 P. falciparum isolates were analyzed by polymorphic regions of msp-1 and msp-2 and classified according to prevalence of allelic families. The majority of patients from all the five sites had mean monoclonal infections of 67·1 and 60·4% of P. falciparum for msp-1 and msp-2, respectively, whereas, mean multiple genotypes of 32·8 and 39·5% for msp-1 and msp-2, respectively. Interestingly, we observed higher multiclonal infection in low transmission area as compared to highly malarious area in the case of msp-1 genotypes, whereas in msp-2 higher multiclonal infection was observed in highly malarious area compared to low transmission area. The overall multiplicities of infection of msp-1 and msp-2 were 1·38 and 1·39, respectively.

CONCLUSION

This is the first report on molecular characterization of P. falciparum field isolates from Jharkhand. The genetic diversity and allelic distribution found in this study is somewhat similar to other reports from India and Southeast Asian countries. However, P. falciparum infection can be highly complex and diverse in these disease-endemic regions of Jharkhand, suggesting continual genetic mixing that could have significant implications for the use of antimalarial drugs and vaccines.

Development of controlled release formulations of imidacloprid employing novel nano-ranged amphiphilic polymers

Amphiphilic copolymers, synthesized from poly (ethylene glycols) and various aliphatic diacids, which self assemble into nano-micellar aggregates in aqueous media, were used to develop controlled release (CR) formulations of imidacloprid [1-(6 chloro-3-pyridinyl methyl)-N-nitro imidazolidin-2-ylideneamine] using encapsulation technique. High solubilisation power and low critical micelle concentration (CMC) of these amphiphilic polymers may increase the efficacy of formulations. Formulations were characterised by Infrared (IR) spectroscopy, Dynamic Light Scattering (DLS) and Transmission Electron Microscope (TEM). Encapsulation efficiency, loading capacity and stability after accelerated storage test of the developed formulations were checked. The kinetics of imidacloprid release in water from the different formulations was studied. Release from the commercial formulation was faster than the CR formulations. The diffusion exponent (n value) of imidacloprid, in water ranged from 0.22 to 0.37 in the tested formulations. While the time taken for release of 50 % of imidacloprid ranged from 2.32 to 9.31 days for the CR formulations. The developed CR formulations can be used for efficient pest management in different crops.