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Phatik T.,Darrang College | Das J.,Defence Research Laboratory DRDO | Boruah P.,Northeast Institute Of Science And Technology Csir
Plant Archives

Antifungal activity of leaf extracts of Polygonum hydropiper and Solanum melongena were tested against Colletotrichum capsici, Curvularia lunata, Rhizoctonia solani and Sclerotinia sclerotiorum, causing severe losses in many economically important crop plants. The ethanolic leaf extracts were found to be effective against the pathogens, when compared with commercial fungicide in-vitro. The maximum zone of inhibition formed by the test extract at 2% concentration were 36.33 mm, 37.33 mm and 30.66 mm in C. lunata, S. sclerotiorum and R. Solani, respectively in P. hydropiper whereas 34.33 mm, 36.24 mm and 32.33 mm in C. capsici, S. sclerotiorum and R. solani respectively in case of S. melongena extracts. It was observed that the inhibitory effect of the commercial fungicide (Dithane M-45) was marginally higher. Source

Nath M.J.,Defence Research Laboratory DRDO | Bora A.,Gauhati University | Talukdar P.K.,Defence Research Laboratory DRDO | Das N.G.,Defence Research Laboratory DRDO | And 3 more authors.
Geocarto International

Assam-Arunachal forest fringed foothill area is endemic for malaria incidence. The present study deals with the temporal analysis of malaria incidence and determines its association with deforestation in 24 villages along the Assam-Arunachal forest fringed foothill area of Sonitpur district of Assam. Malaria epidemiological survey has been carried out in the study area from the year 1994 to 2005. Remote sensing (RS) technique has been used to map the areas of forest changes from the year 2000 to 2005. Geographical information system (GIS) was used to map the malaria incidence and forest cover. The study villages are endemic to malaria infections and there was increasing trend of malaria incidence over the years. The slide positivity rate (SPR) ranged from 5.1% in 1997 to 44.4% in 2005. The percentage forest cover decreased significantly from 23.6% during 2000 to 15.4% during 2005, whereas SPR was increased during 2000-2005. The present study is the first attempt to understand the role of deforestation in malaria incidence using RS and GIS in the north-eastern region of India at a micro-geographic level. The study suggests that the area is endemic to malaria transmission. The decrease in forest cover is a serious ecological concern besides its role in elevating the malaria incidence in the study area. © 2012 Copyright Taylor and Francis Group, LLC. Source

Sarkar M.,Defence Research Laboratory DRDO | Baruah I.,Defence Research Laboratory DRDO | Srivastava R.B.,Defence Research and Development Organisation | Borkotoki A.,Gauhati University | Bhattacharyya I.K.,Cotton College
Pest Management Science

BACKGROUND: Knockdown resistance (kdr) mutation (L1014F) is a well-defined mechanism of resistance to pyrethroids and DDT in many insect species. Sensitive detection of the mutations associated with resistance is a prerequisite for resistance management strategies. The authors have developed a new real-time molecular diagnostic assay based on SimpleProbe ®/melting curve analysis for large-scale kdr genotyping in the wild population of Culex quinquefasciatus Say, the principal vector of bancroftian filariasis. Melting curve analysis is based on the thermal stability difference between matched and mismatched DNA duplexes. The application of SimpleProbe ® chemistry in insects described here is novel in entomology research.RESULTS: The mosquitoes homozygous for knockdown-resistant and knockdown-susceptible allele showed melting peaks at 60.45 °C (± 0.25) and 64.09 °C (± 0.24) respectively. The heterozygous mosquitoes yielded both peaks at approximately 60.5 °C (± 0.2) and 64.20 °C (± 0.23). Among the 92 samples genotyped, 16 were found to be homozygous resistant, 44 homozygous susceptible and 32 heterozygous. Comparative assessments were made of all the reported methods for kdr genotyping.CONCLUSION: The present method is cheaper, faster, more reliable and versatile than other alternatives proposed in detecting correct kdr genotypes in mosquitoes. This is the first report using a single-labelled hybridisation probe to detect point mutations in insect populations. © 2010 Society of Chemical Industry Copyright © 2010 Society of Chemical Industry. Source

Singha I.M.,Defence Research Laboratory DRDO | Kakoty Y.,CSIR - Central Electrochemical Research Institute | Unni B.G.,CSIR - Central Electrochemical Research Institute | Kalita M.C.,Gauhati University | And 4 more authors.
World Journal of Microbiology and Biotechnology

The main objective of this study was to evaluate the effectiveness of crude chloroform extract of Piper betle L. (PbC) in controlling Fusarium wilt of tomato (Lycopersicon esculentum) caused by Fusarium oxysporum f. sp. lycopersici. It was observed that 1% (w/w) amendment of the PbC in soil was more efficient in reducing the Fusarium population in soil than carbendazim and the combined amendment of carbendazim and PbC. Fusarium wilt control studies were carried out in a greenhouse. Variation in different parameters like shoot growth, root growth and mean fresh weights of tomato seedlings in all the treatments were recorded. Accumulation of total phenolics was also studied from the root tissues of tomato. Higher accumulation of total phenolics was observed in the Fusarium-infested plants as compared to that of healthy control and PbC-treated plants. Moreover, it was observed that the extract could reduce the symptoms and disease development. Electron microscopy studies were also done to observe the Fusarium infestation in the vascular bundles and to show the accumulation of total phenolics in the vacuoles of root tissue. © 2011 Springer Science+Business Media B.V. Source

Singha I.M.,Defence Research Laboratory DRDO | Singha I.M.,CSIR - Central Electrochemical Research Institute | Unni B.G.,CSIR - Central Electrochemical Research Institute | Kakoty Y.,CSIR - Central Electrochemical Research Institute | And 4 more authors.
Archives of Phytopathology and Plant Protection

Fourteen medicinal plants belonging to 13 families were collected and extracted with petroleum ether (PE), chloroform, methanol and water to yield 60 crude extracts. Using agar diffusion method, these extracts were evaluated for antifungal activity on the growth of five phytopathogenic fungi. Among all the extracts tested, PE, chloroform and methanol extracts of Piper betle L. and PE and chloroform extracts of Allamanda cathartica exhibited promising antifungal activity. Minimum inhibitory concentration (MIC) values of the above promising extracts were determined using broth dilution technique and observed that chloroform extract of P. betle L. exhibited the least MIC value ranging from 280 to 1130 μg ml -1. In this study, we report chloroform extract of P. betle L. to be thermally stable even when steam sterilised for the first time and that it could be stored at 4°C with almost no change in its activity for a period of 180 days. © 2011 Copyright Taylor and Francis Group, LLC. Source

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