Bhaben Tanti

Analysis of Genetic Diversity of Certain Species of Piper Using RAPD-Based Molecular Markers

The utility of RAPD markers in assessing genetic diversity and phenetic relationships of six different species of Piper from Northeast India was investigated. Polymerase chain reaction (PCR) with four arbitrary 10-mer oligonucleotide primers applied to the six species produced a total of 195 marker bands, of which, 159 were polymorphic. On average, six RAPD fragments were amplified per reaction. In the UPGMA phenetic dendrogram based on Jaccard’s coefficient, the different accessions of Piper showed a high level of genetic variation. This study may be useful in identifying diverse genetic stocks of Piper, which may then be conserved on a priority basis.

Biodegradation of Petroleum Tar by Pseudomonas Spp. From Oil Field of Assam, India

ABSTRACT Petroleum tar produced during the processing of crude oil is one of the earths major pollutants. The potential of certain soil bacteria in the biodegradation of petroleum tar was assessed to develop an active indigenous bacterial consortium for bioremediation of petroleum tar–polluted sites of Assam, India. In vitro enrichment cultures of five Pseudomonas spp. were found to metabolize petroleum tar. The Fourier transform infrared (FTIR) analyses of the enrichment cultures revealed the presence of the functional groups, viz., –OH, –CHO, C˭O, and –COOH, which provided evidence for the biodegradation of petroleum tar. Further, gas chromatography–flame ionization detection (GC-FID) analyses revealed complete degradation of low-molecular-weight hydrocarbons, and the subsequent appearance of some additional peaks reflected the formation of intermediate metabolites during the degradation of petroleum tar. A mixed culture with 0.1% Tween 80 as a surfactant exhibited almost complete degradation in contrast to the degradation by the mixed culture without Tween 80. This confirmed the effect of a surfactant for acceleration of the biodegradation process of petroleum tar.

Freshwater Diatoms from Deepor Beel - A Ramsar Site of Assam,India Revealed Potential Photoluminescence Properties forNanotechnological Applications

Photoluminescence property of few freshwater diatoms was studied form Deepor Beel, a Ramsar site of Assam, India. Diatom, a unicellular, eukaryotic, photosynthetic alga of the class Bacillariophyceae has the natural ability biogeochemical cycling of natural silica and to deposit nanoporous silica over cell frustule. Nanoporous silica with excellent photoluminescence properties become suitable material for wider applications in IT based sector. Keeping view in mind, the present study was undertaken with some freshwater diatoms obtained from an important internationally recognized important freshwater wetland. Four diatom viz. Navicula sp., Thalassiosira sp., Nitzschia sp. and Achanthes sp., treated with acid digestion method were subjected to scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-Vis spectroscopy analysis to characterize their structural properties of the frustules. Photoluminescence properties (PL) of diatom frustules excited at 250 nm, 285 nm and 329 nm showed a diverse range of PL spectra at ultraviolet, green and blue ranges that indicated their potential optoelectronic behaviours. Time-resolved photoluminescence (TRPL) analysis of the diatom frustules, excited at 375 nm revealed the decay time in the range between 3.85 eV to 2.67 eV suggesting the biexponential decay of natural diatoms.

RNAi-derived transgenic resistance to Mungbean yellow mosaic India virus in cowpea

Cowpea is an important grain legume crop of Africa, Latin America, and Southeast Asia. Leaf curl and golden mosaic diseases caused by Mungbean yellow mosaic India virus (MYMIV) have emerged as most devastating viral diseases of cowpea in Southeast Asia. In this study, we employed RNA interference (RNAi) strategy to control cowpea-infecting MYMIV. For this, we generated transgenic cowpea plants harbouring three different intron hairpin RNAi constructs, containing the AC2, AC4 and fusion of AC2 and AC4 (AC2+AC4) of seven cowpea-infecting begomoviruses. The T0 and T1 transgenic cowpea lines of all the three constructs accumulated transgene-specific siRNAs. Transgenic plants were further assayed up to T1 generations, for resistance to MYMIV using agro-infectious clones. Nearly 100% resistance against MYMIV infection was observed in transgenic lines, expressing AC2-hp and AC2+AC4-hp RNA, when compared with untransformed controls and plants transformed with empty vectors, which developed severe viral disease symptoms within 3 weeks. The AC4-hp RNA expressing lines displayed appearance of milder symptoms after 5 weeks of MYMIV-inoculation. Northern blots revealed a positive correlation between the level of transgene-specific siRNAs accumulation and virus resistance. The MYMIV-resistant transgenic lines accumulated nearly zero or very low titres of viral DNA. The transgenic cowpea plants had normal phenotype with no yield penalty in greenhouse conditions. This is the first demonstration of RNAi-derived resistance to MYMIV in cowpea.

Karyomorphology of three species of Aristolochia – rare and endemic medicinal plants of Assam, India

Karyomorphological analyses were conducted of three species of Aristolochia from Assam, India: Aristolochia indica Linn., Aristolochia saccata Wall., and Aristolochia cathcartii Hook. f. The study included determination of somatic chromosome number, total chromosome length, volume, arm ratio and centromeric position. Chromosome classification was done on the basis of the position of the centromere. Their karyotypes were as follows: 2n = 12 for Aristolochia indica Linn. and Aristolochia saccata Wall., and 2n = 20 for Aristolochia cathcartii Hook. f. A. indica consists of six median chromosomes and six metacentric chromosomes. The chromosome length varied from 1.36 μm to 3.06 μm while their volumes ranged from 0.004 μm3 to 0.176 μm3. The relative length of the chromosomes varied from 5.71 μm to 12.85 μm. A. saccata possesses six median, two metacentric and two submetacentric chromosomes. One pair of metacentric chromosome possesses secondary constriction at subterminal region. The chromosome length varied from 1.36 μm to 2.38 μm while their volumes ranged from 0.0046 μm3 to 0.137 μm3. The relative length of the chromosomes varied from 6.25 μm to 10.93 μm. In A. cathcartii, the 20 somatic chromosomes comprised of eight median chromosomes, eight metacentric chromosomes and four submetacentric chromosomes. The chromosome length varied from 1.36 μm to 4.08 μm while their volumes ranged from 0.004 μm3 to 0.235 μm3. The relative length of the chromosomes varied from 2.32 μm to 6.98 μm. The chromosomes of A. indica Linn., i.e. only median and metacentric chromosomes, suggest a more primitive nature.