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Badhai J.,Institute of Life science | Kumari P.,Institute of Life science | Krishnan P.,Central Agricultural Research Institute | Ramamurthy T.,Indian National Institute of Cholera and Enteric Diseases | Das S.K.,Institute of Life science
FEMS Microbiology Letters | Year: 2013

In this study, we characterize 18 cultivable bacteria associated within the mucus of the coral Fungia echinata from Andaman Sea, India. 16S rRNA gene sequence analysis showed that all the 18 strains isolated in this study from the coral mucus belong to the group Gammaproteobacteria and majority of them were identified as Vibrio core group. Our objective was to investigate the presence of the SXT/R391 integrating conjugative elements (ICEs) targeting integrase intSXT and SXT Hotspot IV genetic elements in these isolates. SXT/ICE initially reported in Vibrio cholerae contains many antibiotic and heavy metal resistance genes and acts as an effective tool for the horizontal transfer of resistance genes in other bacterial populations. Two of our strains, AN44 and AN60, were resistant to sulfamethoxazole, trimethoprim, chloramphenicol, and streptomycin, in addition to other antibiotics such as neomycin, ampicillin, rifampicin, and tetracycline. Using PCR followed by sequencing, we detected the SXT/ICE in these strains. The SXT integrase genes of AN44 and AN60 had a 99% and 100% identity with V. cholerae serogroup O139 strain SG24. This study provides the first evidence of the presence of SXT/R391 ICEs in Marinomonas sp. strain AN44 (JCM 18476T) and Vibrio fortis strain AN60 (DSM 26067T) isolated from the mucus of the coral F. echinata. © 2012 Federation of European Microbiological Societies.

Singh D.R.,Central Agricultural Research Institute
Indian Journal of Natural Products and Resources | Year: 2014

The fruits of West Indian Cherry, Malpighia glabra Linn. are of nutritional value because of their very high ascorbic acid content. The present paper gives information on its current status and large scale cultivation prospects in India particularly in Andaman and Nicobar Islands. © 2006, Natural Product Radiance. All rights reserved.

Ahmad I.,Central Agricultural Research Institute | Bhagat S.,Central Agricultural Research Institute
Vegetos | Year: 2013

The biocontrol fungi, Trichoderma spp. are the most important biocontrol agent and have been used extensively worldwide for the management of various plant pathogens. Twenty isolates of Trichoderma (T. harzianum, T. viride and T. hamatum) were isolated from rhizosphere of different crops and location of Andaman district, Andaman and Nicobar Island and tested in vitro against sclerotium rolfsii causing stem rot of brinjal. In vitro test of these antagonist against test pathogen under non-volatile condition revealed that all isolates significantly inhibited the S. rolfsii in vitro (>80% inhibition), but the isolates Th-CARI1 to Th-CARI5 was most effective in parasitizing the test pathogen with >90 % inhibition. Under volatile condition there was a significant variation in the percentage inhibition (16.7% - 61%). PCR- RFLP amplified fragments with ITS1 and ITS4 primer of these isolates showed clear difference among the Trichoderma isolates with overall 69% similarity. However the Trichoderma isolates Thr-1, Tv-3, GH4-1 and Thr 1(2) \ were found 90% similarity.

Pandey C.B.,Central Agricultural Research Institute | Begum M.,Central Agricultural Research Institute
Soil Use and Management | Year: 2010

The decrease in soil fertility in agroecosystems due to continuous harvesting, loss of fine soil and oxidation of soil organic carbon (SOC) is well known. This study evaluates for a humid tropical climate in South Andaman Island, India, the impact of a 15-yr old Pueraria cover crop (CC) under a coconut plantation, with and without phosphorus (P) application, on the soil N mineralization rate (NMR), the mineral N pool (NH4 +-N and NO3 --N), microbial biomass carbon (MB-C) and SM under four treatments, (1) no cover crop (NCC), (2) no cover crop + phosphorus (NCC+P), (3) CC, and (4) cover crop + phosphorus (CC+P) during three seasons, wet (May-October), post-wet (November-January) and dry (February-April). The NCC treatment served as a control. In addition, an ex-situ experiment was conducted to verify the effect of P application on NMR and MB-C under 100% field capacity (FC), 50 and 25% FC representing the different seasons. The NMR, mineral N pool and MB-C increased by 37, 46 and 41%, respectively under the CC compared to the control. SOC and fine soil particles were also greater under the CC by 41 and 461%, respectively, compared to the control. The application of P to the CC increased soil N mineralization, the mineral N pool and MB-C by 33, 16 and 14%, respectively. The amount of mineralized N was greater under the CC and CC+P treatments by 39 and 73%, respectively than the control. The ex-situ experiment showed that the P application increased NMR and MB-C, but the increases were highest in the 50% FC and lowest in 100% FC. It is proposed for the humid tropics that a CC could be used for enhancing SOC and increasing soil N mineralization under coconut plantations and other similar agroecosystems. © 2010 The Authors. Journal compilation © 2010 British Society of Soil Science.

Pandey C.B.,Central Agricultural Research Institute | Singh L.,Central Agricultural Research Institute | Singh S.K.,National Bureau of Soil Survey and Land Use Planning
Forest Ecology and Management | Year: 2011

Role of buttresses as a physical support to trees is well known, however, information on how buttresses form habitat heterogeneity and increase availability of nitrogen (N) in tropical rainforests is not yet much known. This study reports consequence of buttresses induced habitat heterogeneity on build up and supply of mineral N in a tropical rainforest of the South Andaman Islands of India. Treatment included buttresses (upslope) and adjacent (flat) microhabitats. Mineral N (NH4+N and NO3-N) and microbial biomass carbon (MB-C) pools and mineral N supply rate (net nitrification and net soil N mineralization rates) were measured in both microhabitats for consecutive 12months representing wet, post wet and dry seasons. Buttress microhabitats accumulated 7tha -1yr -1 litters, which was 62% higher than adjacent microhabitats. The buttress microhabitats also had 13% more fine soil particles than adjacent microhabitats. Soil organic carbon (SOC), total N, mineral N and MB-C were 18%, 52%, 38% and 34%, respectively higher in the buttress than adjacent microhabitat. However, C/N ratio was lower in the buttress (18) than adjacent microhabitat (23). Net nitrification as well as net soil N mineralization rate was 45% and 44%, respectively higher in the buttress than adjacent microhabitat. High amount of rainfall during wet season reduced the net nitrification rate and NO3-N pool, but increased NH4+N pool; these phenomena probably protected mineral N from leaching losses and enhanced the habitat heterogeneity further. Net nitrification rate, net soil N mineralization rate and MB-C were inversely correlated to the rainfall amount. However, net soil N mineralization rate was positively correlated to MB-C. These observations suggest that buttresses accelerate nitrogen cycling at microhabitat scale and form habitat heterogeneity on a landscape scale (forest floor), which forms pockets of mineral N reserves and simultaneously increases supply of plant available N in the tropical rainforests. © 2011 Elsevier B.V.

Dinesh R.,Central Agricultural Research Institute | Ghoshal Chaudhuri S.,Central Agricultural Research Institute
Ecological Indicators | Year: 2013

The objective of the study was to examine the long-term changes in biochemical/microbial indicators of soil quality due to clear felling of mangroves for establishment of plantations. The biochemical/microbial parameters included dissolved organic-C (DOC) and -N (DON), soil microbial biomass-C (SMBC), -N (SMBN) and -P (SMBP), soil respiration (SR), metabolic quotient (qCO2), adenylates (ATP, AMP and ADP), adenylate energy charge (AEC), ergosterol and their ratios. Results revealed that the undisturbed mangroves possessed considerably greater amounts of soil organic C, DOC and DON. Consequently, SMBC, SMBN and SMBP showed marked reductions in the plantations suggesting an average loss of 66%, 49% and 75%, respectively due to changed land use. Likewise, SR decreased by 46.4% in the plantations. Enhanced qCO 2 levels in the plantations indicated a microbial community under stress with a high maintenance carbon demand, while lower qCO2 levels in the mangroves indicated an efficient microbial community and a better use of available organic substrates. The levels of ATP, AMP and ADP followed a trend identical to that of SMB and SR. Greater ergosterol concentration led to greater ergosterol/SMBC ratio suggesting a shift in the microbial community structure from a primarily fungi dominated SMB in the mangroves to a fungi recessive SMB in the plantations. © 2013 Elsevier B.V. All rights reserved.

Murugan A.V.,Central Agricultural Research Institute | Swarnam T.P.,Central Agricultural Research Institute | Gnanasambandan S.,Regional Plant Quarantine Station
Environmental Monitoring and Assessment | Year: 2013

Pesticides are shown to have a great effect on soil organisms, but the effect varies with pesticide group and concentration, and is modified by soil organic carbon content and soil texture. In the humid tropical islands of Andaman, India, no systematic study was carried out on pesticide residues in soils of different land uses. The present study used the modified QuEChERS method for multiresidue extraction from soils and detection with a gas chromatograph. DDT and its various metabolites, α-endosulfan, β-endosulfan, endosulfan sulfate, aldrin, and fenvalerate, were detected from the study area. Among the different pesticide groups detected, endosulfan and DDT accounted for 41.7 % each followed by aldrin (16.7 %) and synthetic pyrethroid (8.3 %). A significantly higher concentration of pesticide residues was detected in rice-vegetable grown in the valley followed by rice-fallow and vegetable-fallow in the coastal plains. Soil microbial biomass carbon is negatively correlated with the total pesticide residues in soils, and it varied from 181.2 to 350.6 mg kg-1. Pesticide residues have adversely affected the soil microbial populations, more significantly the bacterial population. The Azotobacter population has decreased to the extent of 51.8 % while actinomycetes were the least affected though accounted for 32 % when compared to the soils with no residue. © 2013 Springer Science+Business Media Dordrecht.

Pandey C.B.,Central Agricultural Research Institute | Chaudhari S.K.,Indian Central Soil Salinity Research Institute | Dagar J.C.,Indian Central Soil Salinity Research Institute | Singh G.B.,Indian Central Soil Salinity Research Institute | Singh R.K.,Indian Central Soil Salinity Research Institute
Soil and Tillage Research | Year: 2010

Tillage is known to reduce soil organic carbon (SOC) and increase soil N mineralization, but information on the level of tillage that increases net soil N mineralization and simultaneously maintains a considerable amount of SOC is poorly known. This study investigated the effect of four levels of tillage (15-cm deep by a local made plough) on net soil N mineralization rate (NMR), net nitrification rate (NNR), pools of NO3 --N and NH4 +-N, and microbial biomass carbon (MB-C), water content of soil (WCS) and soil temperature (ST) in a Dystric fluvisols in the hot humid tropical climate of South Andaman Island of India. We hypothesized that: (1) tillage would increase NMR and reduce amount of SOC. But, these changes would depend on frequency of the tillage, i.e. greater would be the tillage frequency; higher, the NMR and decline in the amount of SOC; (2) low tillage would increase NMR, but reduce SOC nearly equal to short term zero tillage. Tillage levels included: (1) long term zero till (not tilled from 1983 to 2002; then from 2003 to 2006 crops (maize-okra rotation) were sown by dibbling, and weeds were cut and mulched), (2) frequent till (tilled three times before each crop sowing in the crop rotation from 1983 to 2002 and 2003 to 2006 as well; weeds were removed), (3) low till (not tilled from 1983 to 1999; then tilled once before each crop sowing in the crop rotation from 2000 to 2002 and weeds were removed; from 2003 to 2006 tilled like 2000-2002, but weeds were uprooted and buried in situ), and (4) short term zero till (from 1983 to 2002 tillage history was the same as in the low till; from 2003 to 2006 the crops were sown by dibbling in the crop rotation and weeds were cut and mulched in situ). Maize (Zea mays L.) was cultivated during wet season (WS, May to October) and okra (Abelmoschus esculentus L.) during post-wet season (PWS, November to January) in all tillage treatments. Soils were sampled in all tillage treatments (levels) across the WS, PWS and dry (DS, February to April) seasons over two annual cycles (2004-2005 and 2005-2006) and analyses were done for the parameters investigated. We found that WCS was the highest (44-48%) during the WS and the lowest (10-16%) during the DS, however, ST was the lowest (25.5-26.5°C) during the WS and the highest (30.5-33.4°C) during the DS in all tillage treatments. Across the tillage levels, NMR increased from 1.06 to 1.96μgg-1day-1 and NNR from 1.21 to 1.88μgg-1day-1, and pools of NO3 --N and NH4 +-N from 3.98 to 11.1μgg-1 and 24.76 to 42.51μgg-1, respectively. The increase was, however, the highest in the frequent till and the lowest in the long term zero till treatment. The NMR and NNR were the lowest (0.53-0.93μgg-1day-1 and 0.49-0.86μgg-1day-1, respectively) during the WS and the highest (1.09-1.71μgg-1day-1 and 1.06-1.61μgg-1day-1) during the PWS in all tillage treatments. The NMR was positively correlated with the MB-C in all tillage treatments. Concurrent with the increase in the NMR, the SOC declined in all tillage treatments, but the decline was the highest in the frequent till and the lowest in the long term zero till treatment. Across the tillage treatments, the MB-C was correlated to the SOC. The SOC in the low till (7.9mgg-1) treatment was nearly equal to that in the short term zero till treatment (8.8mgg-1), but NMR was higher (0.86μgg-1day-1) particularly during the WS when plant's demand for N is usually high. Our results supported both the hypotheses, and suggested that low tillage might be a good option for soil fertility maintenance and carbon stock build-up in the soils of the hot humid tropics. © 2010 Elsevier B.V.

Singh D.R.,Central Agricultural Research Institute | Srivastava A.K.,Central Agricultural Research Institute | Srivastava A.,Central Agricultural Research Institute | Srivastava R.C.,Central Agricultural Research Institute
Indian Journal of Biotechnology | Year: 2011

A total of 22 accessions of 3 Morinda spp. (Family: Rubiaceae), namely, M. citrifolia, M. tinctoria and M. pubescens were collected from three geographical locations of India, viz., Andaman and Nicobar Islands, Tamil Nadu and Karnataka. RAPD (52) and ISSR (60) primers were employed as genetic marker to study the genotypic variation within and between Morinda spp. In RAPD, only 26 primers amplified and gave reproducible fragments, of which 11 primers were polymorphic. Among 1767 amplified DNA fragments obtained, 953 (54.33%) were polymorphic. The accessions AHD and SHE-1 were the most closely related cultivars with the highest similarity index (0.943) and BBD and MAA-1 were the most distantly related cultivar with lowest similarity index (0.387). In ISSR, of 60 primers tested, 22 gave clear and reproducible fragments. In total, 1892 fragments of different lengths were amplified, of which 1052 bands (56.02%) were polymorphic. According to ISSR results, the two most closely related cultivars were MTC and JGH with the highest similarity index (0.944) and the most distantly related cultivars were BMN with MEM and BGL-2 with lowest similarity index (0.248). Polymorphism and similarity index values for both RAPD and ISSR systems showed that both marker systems are equally effective for diversity analysis in Morinda species.

Pandey C.B.,Central Agricultural Research Institute | Pandey C.B.,Indian Central Soil Salinity Research Institute | Singh G.B.,Indian Central Soil Salinity Research Institute | Singh S.K.,Indian Central Soil Salinity Research Institute | Singh R.K.,Indian Central Soil Salinity Research Institute
Plant and Soil | Year: 2010

Conversion of tropical forests to agricultural land uses is known to alter soil nitrogen (N) transformation processes and microbial biomass carbon (MB-C), which affect productivity and stability of the derived land uses. Information about how conversion of moist evergreen forest to agricultural land uses affects soil nitrogen (N) transformation processes and MB-C in hot humid tropics is meager. The present study explores the following questions: (1) how does conversion of native moist evergreen forest to agricultural production systems (grassland, home garden and silvopasture) affect net soil N mineralization rates, pools of mineral nitrogen (NH4 +- N and NO3 -- N) and MB-C in the hot humid tropical climate of South Andaman, India and (2) are changes in soil N transformations and MB-C related to differences in soil moisture and temperature induced with forest conversion? Variations in net soil N mineralization, NH4 +- N and NO3 -- N pools, MB-C and soil temperature and moisture were measured across wet, post-wet and dry seasons at ten sites of each derived agricultural land use and native forest. In addition, inputs of carbon (C) and N to the soils and outputs of C and N from the land use systems through harvests were also measured. We measured the N mineralization rate by the buried bag technique using 2 M KCl as an extractant. The NO3 -- N and NH4 +- N were measured at the beginning and end of incubation. The MB-C was measured by a chloroform fumigation-extraction method. We found that forest conversion resulted in a decline in carbon input, but caused rise in soil temperature (from 0. 4 to 9. 8% across the seasons) in derived agricultural land uses compared to native forest. The soil temperature increase was the highest in the grassland and lowest in the home garden. Across the three seasons, net soil N mineralization rates increased 27 to 55 % in the derived agricultural land uses compared to the native forest, with the increase highest in the grassland and lowest in the home garden. Soil organic C (SOC), MB-C, and NO3 - declined in the derived agricultural land uses relative to native forest, with the greatest effect again seen in the grassland. These observations suggest that native forest conversion to agricultural uses results in lower soil organic C content over time, due to increased mineralization rates stimulated by a rise in soil temperature, and that these soil changes may be most pronounced in grasslands. Therefore, tree based land uses offer good options for soil carbon build up and protection against N loss in the hot humid tropics. © 2010 Springer Science+Business Media B.V.

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