Showing papers in "Current Science in 2003"

Biosynthesis of metal nanoparticles using fungi and actinomycete

Abstract: There is little doubt that nanomaterials will play a key role in many technologies of the future. One key aspect of nanotechnology concerns the development of reliable experimental protocols for the synthesis of nanomaterials over a range of chemical compositions, sizes and high monodispersity. In the context of the current drive to develop green technologies in materials synthesis, this aspect of nanotechnology assumes considerable importance. An attractive possibility is to use micro-organisms in the synthesis of nanoparticles. In this article, we provide a brief overview of the research efforts worldwide on the use of micro-organisms in the biosynthesis of inorganic nanoparticles, with particular emphasis on the recent and exciting results obtained at the National Chemical Laboratory, Pune on the biosynthesis of noble-metal nanoparticles using fungi and actinomycete. Some of the challenges in this emerging approach are highlighted.

Global review of commercialized transgenic crops

Abstract: THE unprecedented rapid adoption of transgenic crops during the initial five-year period (1996 to 2000) when genetically modified (GM) crops were first adopted, reflects the significant multiple benefits realized by large and small farmers in industrial and developing countries that have grown transgenic crops commercially. Between 1996 and 2000, a total of fifteen countries – 10 industrial and 5 developing – contributed to more than a twentyfive fold increase in the global area of transgenic crops from 1.7 million hectares in 1996 to 44.2 million hectares in 2000. The accumulated area of transgenic crops planted in the five-year period 1996 to 2000 total 125 million hectares, equivalent to more than 300 million acres. Adoption rates for transgenic crops are unprecedented and are the highest for any new technology by agricultural industry standards. High adoption rates reflect grower satisfaction with products that offer significant benefits ranging from more convenient and flexible crop management, higher productivity and/or net returns per hectare, health benefits and a safer environment through decreased use of conventional pesticides, which collectively contribute to not only improved weed and insect pest control (attainable with transgenic herbicide-tolerant and insect-resistant Bt crops) but also benefits of lower input and production costs; genetically modified crops offer significant economic advantages to farmers compared with corresponding conventional crops. The severity of weed and insect pests varies from year to year and hence this will have a direct impact on pest control costs and the consequent economic advantage. Despite the on-going debate on GM crops, particularly in countries of the European Union, millions of large and small farmers in both industrial and developing countries continue to increase their plantings of GM crops because of the significant multiple benefits they offer. This high adoption rate is a strong vote of confidence in GM crops, reflecting grower satisfaction. Many recent studies have confirmed that farmers planting herbicide-tolerant and insect-resistant Bt crops are more efficient in managing their weed and insect pests. An estimated 3.5 million farmers grew transgenic crops to health and economic advantages. In coming years, the number of farmers planting GM crops is expected to grow substantially and the global area of GM crops is expected to continue to grow. Global population would exceed 6 billion by 2050, when approximately 90% of the global population will reside in Asia, Africa and Latin America. Today, 815 million people in the developing countries suffer from malnutrition and 1.3 billion are afflicted by poverty. Transgenic crops, often referred to as GM crops, represent promising technologies that can make a vital contribution to global food, feed and fibre security. Global reviews of transgenic crops have been published as ISAAA Briefs annually since 1996. This publication provides the latest information on the global status of commercialized transgenic crops. A detailed global data set on the adoption of commercialized transgenic crops is presented for the year 2001 and the changes that have occurred between 2000 to 2001 are highlighted. The global adoption trends during the last six years from 1996 to 2001 are also illustrated. Given the continuing debate on transgenic crops, particularly the issues relating to public acceptance, there has been much speculation as to whether the global area of transgenic crops would continue to increase in 2001. This publication documents the global database on the adoption and distribution of GM crops in 2001. Note that the words transgenic crops and genetically modified crops, maize and corn, as well as rapeseed and canola are used synonymously in the text, reflecting the usage of these words in different regions of the world. Global figures and hectares planted commercially with transgenic crops have been rounded off to the nearest 100,000 hectares. In some cases this leads to insignificant approximations and there may be slight variances in some figures, totals and percentage estimates. It is also important to note that countries in the Southern Hemisphere plant their crops in the last quarter of the calendar year; the transgenic crop areas reported in this publication are planted, not harvested, hectarage in the year stated. Thus, the 2001 information for Argentina, Australia, South Africa and Uruguay is hectares planted in the last quarter of 2001.

Acclimatization of tissue cultured plants

Abstract: A substantial number of micropropagated plants do not survive transfer from in vitro conditions to greenhouse or field environment. The greenhouse and field have substantially lower relative humidity, higher light level and septic environment that are stressful to micropropagated plants compared to in vitro conditions. The benefit of any micropropagation system can, however, only be fully realized by the successful transfer of plantlets from tissue-culture vessels to the ambient conditions found ex vitro. Most species grown in vitro require an acclimatization process in order to ensure that sufficient number of plants survive and grow vigorously when transferred to soil. This article reviews current and developing methods for the acclimatization of micropropagated plantlets.

Rainwater harvesting as an adaptation to climate change

Abstract: Extreme climate events such as aridity, drought, flood, cyclone and stormy rainfall are expected to leave an impact on human society. They are also expected to generate widespread response to adapt and mitigate the sufferings associated with these extremes. Societal and cultural responses to prolonged drought include population dislocation, cultural separation, habitation abandonment, and societal collapse. A typical response to local aridity is the human migration to safer and productive areas. However, climate and culture can interact in numerous ways. We hypothesize that people may resort to modify dwelling environments by adapting new strategies to optimize the utility of available water by harvesting rain rather than migrating to newer areas. We review recent palaeoclimatological evidence for climate change during the Holocene, and match those data with archaeological and historical records to test our 'climate change-rainwater harvest' hypothesis. We find correlation between heightened historical human efforts for construction of rainwater harvesting structures across regions in response to abrupt climate fluctuations, like aridity and drought. Historical societal adaptations to climate fluctuations may provide insights on potential responses of modern societies to future climate change that has a bearing on water resources, food production and management of natural systems.

Hydrogen from biomass

Abstract: Hydrogen is considered as a novel fuel for the twenty-first century, mainly due to its environmentally benign character Production of hydrogen from renewable biomass has several advantages compared to that of fossil fuels A number of processes are being practised for efficient and economic conversion and utilization of biomass to hydrogen This article updates the developments of various hydrogen-production processes from biomass Several developmental works are discussed, with a brief outline of different technologies employed therein A comparative study of existing processes is given on the basis of their relative merits and demerits In addition, some techno-economic considerations of hydrogen-production processes from biomass are also highlighted

Biofilms: A survival strategy of bacteria

Abstract: Bacterial biofilm is a structured community of bacterial cells enclosed in a self-produced polymeric matrix and adherent to an inert or living surface, which constitutes a protected mode of growth that allows survival in hostile environment. The biofilm-forming microorganisms have been shown to elicit specific mechanisms for initial attachment to a surface, formation of microcolony leading to development of three-dimensional structure of mature biofilm. They differ from their free-living counterparts in their growth rate, composition and increased resistance to biocides, antibiotics and antibodies by virtue of up regulation and/or down regulation of approximately 40 per cent of their genes. This makes them highly difficult to eradicate with therapeutic doses of antimicrobial agents. A greater understanding of mechanism of their formation and survival under sessile environments may help in devising control strategies.

Antimalarial agents from plant sources

Abstract: The success of the antimalarial drug quinine and the discovery of artemisinin, the most potent antimalarial drug, both from plant sources, has led to the study of plants as antimalarial agents. The ethnopharmacological approach for the search of new antimalarial agents from plant sources has proved to be more predictive. This article gives a critical account of crude extracts, essential oils and secondary plant metabolites with diverse chemical structure possessing antimalarial activity against different malarial parasites. The major leads have been highlighted and some reported structure-activity relationships and their possible modes of action discussed.

A note on early earthquakes in northern India and southern Tibet

Abstract: The scientific contribution in this communication is threefold: (i) the presentation of new evidence or early, pre-19th century large earthquakes in the Himalaya, (ii) the preliminary interpretation of data that have beenidentified up to now and (iii) that currently no forecast for the timing and magnitude of future large events is possible.

Droughts of the Indian summer monsoon: Role of clouds over the Indian Ocean

Abstract: Comparison of the evolution of the normal summer monsoon of 2003 with the unanticipated drought of 2002 led to this investigation of the role of the deep convection in the atmosphere (deep cloud systems) over the equatorial Indian Ocean We find that the link of the Indian monsoon to events over the equatorial Indian Ocean is as important as the well-known link to the dramatic events over the Pacific (El Nino Southern Oscillation; ENSO) Over the equatorial Indian Ocean, enhancement of deep convection in the atmosphere over the western part is generally associated with suppression over the eastern part and vice versa We call the oscillation between these two states, which is reflected in the pressure gradients and the wind along the equator, the Equatorial Indian Ocean Oscillation (EQUINOO) We show that every season with excess rainfall/drought during 1979-2002 can be 'explained' in terms of favourable/unfavourable phase of either this oscillation or the ENSO or both In particular, in the monsoon season of 2002 while the ENSO phase was unfavourable but weak, the phase of the EQUINOO was highly unfavourable and a large deficit occurred in the monsoon rainfall

Antifungals from fluorescent pseudomonads: biosynthesis and regulation

Abstract: A group of root-associated bacteria, plant growth-promoting rhizobacteria (PGPR), intimately interact with the plant roots and consequently influence plant health and soil fertility. Among these PGPR, fluorescent psuedomonads occur commonly in the rhizosphere of plants and help suppress disease establishment and spread. Psuedomonads suppress soil-borne fungal pathogens by producing antifungal metabolites such as pyoluteorin, pyrrolnitrin, phenazines, and 2,4-diacetyl phloroglucinol. In addition, psuedomonads can indirectly suppress fungal pathogens by scavenging iron in the rhizosphere environment through the release of siderophores. Considering the global significance of antifungal metabolites in disease suppression and consequent applicability of psuedomonads in biological control strategies, biosynthesis and regulation of these molecules is discussed in this review to highlight new developments in the subject.

Endophytic fungal communities in leaves of tropical forest trees: Diversity and distribution patterns

Abstract: Endophytic fungi cause symptomless infections in healthy tissues of plants This cryptic guild of fungi is regarded as a benchmark for estimating fungal biodiversity We studied endophyte distribution, diversity and host recurrence in 24 tree hosts (belonging to 17 plant families) of two dry tropical forests of the Nilgiri Biosphere Reserve A total of 81 endophyte taxa were isolated from 3600 tissue segments Fifty-six species were isolated from more than one host We discerned two groups of fungi in both forests, one group consisting of the ubiquitous forms that dominated the endophyte assemblage of many hosts and the second represented by the less frequent forms Host density influenced the composition and distribution of endophytes in one of the forests The existence of ubiquitous forms reduced the diversity of the endophytes in the plant communities Our results suggest that dry tropical forests are not hyperdiverse with reference to endophytes and that the generalists among endophytes be identified before extrapolating data to calculate global fungal diversity

Nanophase materials by hydrothermal, microwave- hydrothermal and microwave-solvothermal methods

Abstract: Hydrothermal, microwave-hydrothermal and microwave-solvothermal methods are truly low temperature methods for the prearation of nanophase materials of different sizes and shapes. These methods save energy and are environmentally benign because the reactions take place in closed system conditions. The nanophase materials can be produced in either a batch or co ntinuous process using the above methods. Oxide materials such as zirconia, titania and various spinel ferrites and metals such as Pt, Pd, Ag, Au, etc . of different sizes and shapes were crystallized in our lab oratory using the hydrothermal, microwave-hydrothermal and microwave-solvothermal methods. The key novelty of our work is the use of microwave -assisted reactions to dramatically enhance the kinetics of crystallizati on by one to two orders of magnitude.

Environmental classification of mangrove wetlands of India

Abstract: THE coastal zone of the mainland of India and Andaman and Nicobar islands is endowed with the presence of ex tensive and diverse mangrove wetlands. These mangrove wetlands act as a barrier against cyclones, avoid coastal erosion and provide nursery grounds for a number of commercially-important fish, prawns and crabs. Some of these mangrove wetlands play an important role in en hancing the fishery production of the adjacent neritic waters by exporting organic and inorganic nutrients 1 . The environmental setting of this multi ple-use ecosystem is governed by physical forces such as geomorphology of the coast, climate, tidal amplitude and duration, and quantity of freshwater inflow 2–4 . These macro-level environmental factors of mangrove wetlands undergo changes both in time and space, and these changes are reflected in the mangrove forest composition and structure 5,6 . Understanding the development of mangrove forest communities through time, with reference to changing environmental condition, is a basic requirement to de velop and implement mangrove conservation and management plans. In this article the environmental setting of the mangrove wetlands of India are described and a classification system is provided. Changes in the floristic and forest structure of these mangrove wetlands due to changes in some of the macro-level environmental factors are also discussed.

Isolation of plant growthpromoting strains of bradyrhizobium (arachis) sp. with biocontrol potential against macrophomina phaseolina causing charcoal rot of peanut

Abstract: Among ten strains of Bradyrhizobium (Arachis) sp. in peanut, only three produced siderophore and IAA, and exhibited phosphate solubilization in vitro. Bradyrhizobium strains AHR-2 a m P + , AHR-5 a m P + and AHR-6 a m p + showed antagonistic activity against Macrophomina phaseolina. Peanut seeds coated with Bradyrhizobium strains were significant by enhanced seed germination, seedling biomass, nodule number, nodule fresh weight, average nodule weight compared to uninoculated and uninfected controls. These findings confirm the antagonistic as well as plant growth-promotory properties of Bradyrhizobium strains.

Periodic minimal surfaces of cubic symmetry

Abstract: A survey of cubic minimal surfaces is presented, based on the concept of fundamental surface patches and their relation to the asymmetric units of the space groups. The software Surface Evolver has been used to test for stability and to produce graphic displays. Particular emphasis is given to those surfaces that can be generated by a finite piece bounded by straight lines. Some new varieties have been found and a systematic nomenclature is introduced, which provides a symbol (a 'gene') for each triply-periodic minimal surface that specifies the surface unambiguously.

A sediment budget for the Ganga-Brahmaputra catchment

Abstract: Published data are used to construct an approximate sediment budget for the 1.656 × 10 6 km 2 catchment of the Ganga and Brahmaputra rivers. From these data, it has not been possible to identify the major sources of sediment. Recently published Nd/Sr tracer results suggest that the High Himalaya is the main source of sediment, providing for the first time a focus for more detailed research on the role of land use and other factors in the generation of sediment. Much is yet to be learned about this globally important catchment, and the budget provides a framework for further research.

Genetic engineering for virus resistance

Abstract: Plant virus diseases cause severe constraints on the productivity of a wide range of economically important crops worldwide. In India the Green Revolution ushered in intensive agricultural practices and reduced varietal diversity, resulting in the emergence of viral diseases at an alarming pace in the cultivated crops. Some such diseases, which are especially relevant to India, along with their yield losses, are listed in Table 1. Strategies for the management of viral diseases normally include control of vector population using insecticides, use of virus-free propagating material, appropriate cultural practices and use of resistant cultivars. However, each of the above methods has its own drawback. Rapid advances in the techniques of molecular biology have resulted in the cloning and sequence analysis of the genomic components of a number of plant viruses. A majority of plant viruses have a single-stranded positivesense RNA as the genome. However, some of the most important viruses in tropical countries like India have single-stranded and double-stranded DNA genomes and RNA genomes of ambisence polarity, i.e. genes oriented in both directions. An excellent book is now available on the organization of plant viral genomes. Genome organization, electron-microscopic structures and symptoms caused by some of the viruses, referred to in this review, are briefly illustrated in Figure 1. Concomitantly, tremendous advances have taken place in our understanding of plant–virus interaction in the process of pathogenesis and resistance. This, along with associated advances in the genetic transformation of a number of crop plants, have opened up the possibility of an entirely new approach of genetic engineering towards controlling plant virus diseases. There are mainly two approaches for developing genetically engineered resistance depending on the source of the genes used. The genes can be either from the pathogenic virus itself or from any other source. The former approach is based on the concept of pathogen-derived resistance (PDR). For PDR, a part, or a complete viral gene is introduced into the plant, which, subsequently, interferes with one or more essential steps in the life cycle of the virus. This was first illustrated in tobacco by the group of Roger Beachy, who introduced the coat protein (CP) of tobacco mosaic virus (TMV) into tobacco and observed TMV resistance in the transgenic plants. The concept of PDR has generated lot of interest and today there are several host–virus systems in which it has been fully established. Non-pathogen-derived resistance, on the other hand, is based on utilizing host resistance genes and other genes responsible for adaptive host processes, elicited in response to pathogen attack, to obtain transgenics resistant to the virus. The use of non-PDR type of resistance, even though reported much less in the literature in comparison to PDR-based approaches, holds a better promise to achieve durable resistance. Various aspects of the above topics have been reviewed extensively.

Strategies for development of fungus-resistant transgenic plants

Abstract: AFTER centuries of improving crop plants by breeding for desirable traits, agricultural scientists are now using the tools of molecular biology and genetic engineering to develop transgenic plants with the desired genes. Enormous progress has been made over the past decade in our understanding of the highly complex molecular events that occur in plant–pathogen interactions. This knowledge in turn has provided a number of options and strategies which can be and have been used to make transgenic plants resistant to pathogens. This review deals with fungal pathogens of crop plants. Starting from the first step of mutual recognition of host and pathogen which involves resistance gene–avirulence gene interaction , moving onto immediate response of the plant in terms of hypersensitive response, production of active oxygen species, followed by local resistance response in terms of production of pathogenesis-related proteins and other antifungal proteins, then to the final step of syste-mic acquired resistance (SAR), all this information has been/or is being used to produce fungus-resistant trans-genic plants in different crop species. In this review we discuss strategies that have been used to produce fungus-resistant transgenic plants and also discuss some of the emerging possibilities in the wake of large scale genome sequencing projects being undertaken in crop plants. Significant yield losses due to fungal attacks occur in most of the agricultural and horticultural species. In Indian context, fungal diseases are rated either the most important or second most important factor contributing to yield losses in our major cereal, pulse and oilseed crops. On the basis of a recent survey 1 , contribution of fungal diseases towards total yield loss in some important crops in India has been summarized in Table 1. Incidence of plant diseases has been controlled by agronomic practices that include crop rotation and use of agrochemicals and by breeding new strains and varieties that contain new resistance conferring genes. The use of agrochemicals poses many dangers that include harmful effects on the ecosystem and an increase in the input cost of the farmers. The breeding of resistant crops is time consuming and has to be a continuous process as often new races of pathogens evolve and crops become susceptible. Despite the boom and bust cycles, breeders have been successful in protecting some of the major crops grown around the world from fungal diseases. A major success story is wheat in which systematic breeding has been done to develop varieties …

Fluoride and other inorganic constituents in groundwater of Guwahati, Assam, India

Abstract: Groundwater quality in Guwahati has been studied with special reference to the presence of fluoride The Brahmaputra river in the north, hills to the east and south, and alluvial soil to the west surround the city Fluoride, above the guideline values of WHO, has been found in groundwater of the eastern and southern plains of the city The fluoride contents have positive correlation with Na + , K + , total alkalinity and depth of source, and negative correlation with Mg 2 + , Ca and total hardness Negative correlation of fluoride with hardness and absence of any correlation with chloride indicate recharge of the aquifer by the Brahmaputra and/or rain A few of the samples showed high nitrate and sulphate contents The sources of fluoride and nitrate are suspected to be minerals from the Precambrian granite, which forms the basement of the city and also outcrops at several places in the city

Regeneration and genetic transformation of grain legumes: An overview

Abstract: Grain legume crops like pigeonpea, chickpea, mungbean, groundnut and soybean are extensively grown in the rainfed and dryland areas of India. These legume crops are a source of dietary protein, especially for the largely vegetarian population of sub-tropics. Despite large acreage under these crops, total productivity remains low and has been stagnating for the last few decades. A number of biotic and abiotic stresses are severely affecting full realization of the yield potential of these crops. There is need to increase productivity and enhance the nutritional value of these pulse crops. Cultivars resistant to biotic and abiotic stresses and which have better protein quality and quantity are needed. Grain legumes have a narrow genetic base since they are essentially self-pollinated (although cross-pollination does take place, it is at very low frequency). Thus, there is need to widen the genetic base and incorporate desirable characters. There is an urgent need to use transgenic technologies for improvement of leguminous crops. Worldwide, soybean is the only transgenic grain legume being cultivated in nearly 63% of the total area under transgenics. Routine transformation protocols are limited in most grain legumes. The low success has been attributed to poor regeneration ability (especially via callus) and lack of compatible gene delivery methods, although some success has been achieved in soybean. This review is an attempt to summarize the studies on regeneration and genetic transformation in soybean, pigeonpea, chickpea, pea, groundnut, and Vigna spp. and to identify the hurdles being faced in the efficient recovery of transgenic plants. The review presents a comparative account of explants used, mode of regeneration (organogenesis v/s embryogenesis), gene delivery techniques and recovery of transgenics in crops considered here. Plant tissues regenerate in vitro through two pathways, namely ‘organogenesis’ wherein shoot buds are organized by concerted meristematic activity of a number of cells and ‘embryogenesis’, where usually single cell or a small cluster of cells undergo differentiation to produce somatic embryos similar to zygotic embryos. The regeneration of complete plants via tissue culture has made it possible to introduce foreign genes into plant cells and recover transgenic plants. Morphogenesis could occur directly from the explant or indirectly via the formation of a dedifferentiated callus (Figure 1). However the different pathways of regeneration, viz. organogenesis from callus (pathway I), embryogenesis from callus (pathway IV), organogenesis directly from explants (pathway II) and embryogenesis from explants in a direct mode (pathway III) vary in their amenability to different gene delivery techniques. Although many different techniques (electroporation of intact tissues, silicone carbide whiskers, etc.) have been tested for gene delivery to plant cells, two major methods, namely Agrobacterium-mediated and particle bombardment, have been extensively employed for genetic transformation of crop plants. Regeneration via the callus lends itself easily (compared to explants regenerating directly) to Agrobacterium-mediated transformations, while direct regeneration is more amenable for particle bombardment. Organogenesis from an unorganized callus (pathway I) has only been reported in soybean and pea, where shoots were recovered from callus tissues at a low frequency. Thus, this pathway, although amenable to Agro-

SPOT vegetation multi temporal data for classifying vegetation in south central Asia

Abstract: Satellite remote sensing has enabled the acquisition of land use/land cover and vegetation information at different spatial and temporal scales. Vegetation instrument on-board Spot 4 satellite with four spectral bands - blue (0.43-0.47 μm), red (0.61-0.68 μm), infrared (0.78-0.89 μm) and short wave infrared (1.58-1.75 μm) at a spatial resolution of 1 km and temporal resolution of 1 day meets the requirement of vegetation mapping at a continental scale. This study focuses on the use of multitemporal SPOT VEGETATION data for vegetation mapping in south central Asia. The basis of classification is temporal dynamics, i.e. the pattern of change of Normalized Difference Vegetation Index (NDVI) values through a temporal domain which reflects the phenology of vegetation, crop cycle and the cropping system of agricultural practices. The temporal profile of NDVI facilitates the discrimination between different vegetation types and different types of cropping pattern.

Evolution of disjunct distributions among wet-zone species of the Indian subcontinent: Testing various hypotheses using a phylogenetic approach

Abstract: Disjunct distributions among wet-zone taxa of the Indian subcontinent have intrigued biologists for decades. Most authors have invoked variations of either the dispersal or the vicariance model to explain disjunct distribution. However, some have noted that incorrect taxonomy, due to convergence in morphological characters, can erroneously suggest disjunct distribution. An appropriate approach to test these models (vicariance, dispersal and convergence) is to use molecular phylogenetic methods. A survey of recent molecular phylogenetic studies on Indian systems with disjunct distribution suggests that convergence may be quite common. Therefore, I propose that the first step in studying disjunct distributions is to determine if the observed pattern is real (true disjunct) and not due to convergence, i.e. an artifact of incorrect taxonomy (false disjunct).

The current status of plant transformation technologies

Abstract: Plant transformation vectors and methodologies have been improved to increase the efficiency of plant trans - formation and to achieve stable expression of transgenes in plan ts. Due to the simplicity of the transformation system and precise integration of transgenes, Agro- bacterium Ti plasmid -based vectors continue to offer the best system for plant transformation. Binary vectors have been improved by the incorporation of supe rvirulent vir genes, matrix attachment regions (MAR) and the inser- tion of introns in marker genes and reporter genes. With these improvements and with the use of acetosyringon e, transformation of monocotyledon ous plants using Agro- bacterium has almost become a routine process. The green fluorescent protein (GFP) gene has been extensively modified for plant codon preference, ER/plastid targeting and for greater solubility thereby making it a versatile vital reporter for transgenic plants. Significant progr ess is seen in developing transgenic plants devoid of antibiotic marker genes. Cotransformation of multiple T-DNAs, site-specific recombination strategies and deploy ment of Ac/Ds-based transposition have helped in the elimination of marker genes in transg enic plants. Positive selection strategies using ipt, xylose isomerase and phospho-mannose isomerase have been demonstrated to be useful in many crop plants. The development of BIBAC vectors, a demonstrated capability to transfer multiple genes of a pathway and successful T-DNA tagging in rice, signal the readiness with which transformation technologies can be deployed for the study of 'functional genomics' in plants. The particle bombardment system continues to find use in organelle transformation and tran sformation of plants that lack efficient regeneration systems. A detailed understanding of gene silencing has led to the design of vectors that minimize transgene silencing while ensuring desired levels of transgene expression. Efforts are underway to unde rstand the mechanism of T -DNA integration in plants so that 'knock out' mutagenesis and homology-based gene replacements can be achieved in plants. We review in this article the current status of transformation technologies. An overview of the status of deployment of plant transformation technologies in India is also presented. Plant transformation is performed using a wide range of tools such as Agrobacterium Ti plasmid vectors, microprojectile bombardment, microinjection, chemical (PEG) treatment of prot oplasts and electroporation of protoplasts. Though all methods have advantages that are unique to each of them, transformation using Agrobac- terium and microprojectile bombardment are currently the most extensively used methods 1 . Recent develop- ments in t hese two technologies have been reviewed together with the phenomenon of 'gene silencing' that has come to centrestage after a large number of trans - genic plants have been carefully evaluated for transgene expression in successive generations.

Sonochemistry and its application to nanochemistry

Abstract: This article introduces the field of sonochemistry to scientists and to people interested in science. The article presents the principles of the effect of ultrasound radiation on liquids and solutions. In particular, it discusses the applications of sonochemistry to the chemistry of materials. The article emphasizes the activity of my group in the field.

Characterization of rust on ancient Indian iron

Abstract: Experimental techniques for qualitative and quantitative analysis of rust have been reviewed. Rusting of iron in atmospheric and soil environments has also been briefly reviewed. The application of important spectroscopicmethods (like Raman spectroscopy, infrared spectroscopy and Mossbauer spectroscopy) has been highlighted. X-ray diffraction techniques to understand global as well as local character of rust have been discussed. The techniques have been illustrated with suitable examples of atmospheric rust on ancient Indian irons.

Genetic engineering of crop plants for insect resistance

Abstract: TOOLS of molecular biology and genetic engineering have provided humankind with unprecedented power to manipulate and develop novel crop genotypes towards a safe and sustainable agriculture in the 21st century. Technologies and chemical inputs that have proven harmful to human health and environment need to be replaced with safer alternatives to manage insect pests in agricultural ecosystems. Many insecticidal proteins and molecules are available in nature which are effective against agriculturally important pests but are innocuous to mammals, beneficial insects and other organisms. Insecticidal proteins present in Bacillus thuringiensis (Bt), which have shown efficacy as spray formulations in agriculture over the past five decades, have been expressed in many crop species with positive results. Large scale cultivation of Bt-crops raises concerns about the possible development of resistant insects. Many strategies have been formulated to prevent/delay the development of resistance. These strategies have to be given serious consideration in India where the first Bt-crop containing resistance to insect pests, particularly Helicoverpa armigera, has been released for commercial cultivation in the farmers’ fields. In addition to Bt, proteinase inhibitors present in several plant species offer a good source of resistance to insect pests. A combination of proteinase inhibitors has been suggested as a viable alternative to Bt to manage insects such as H. armigera. In recent years, several novel insecticidal proteins have been discovered in bacteria such as Photorhabdus luminescens. The judicious expression of multiple insecticidal proteins that differ in their mechanisms of toxicity will provide formidable barriers for insects to develop resistance. Finally, deployment of integrated pest management (IPM) strategies during the cultivation of transgenic crops will ensure durable insect resistance. Insect pest menace is the major factor that destabilizes crop productivity in agricultural ecosystems. A variety of insect pests ranging from lepidopterans to orthopterans damage crops and stored seed. The rich biodiversity of agricultural, horticultural and forest species faces a perpetual onslaught by insect infestation because of the predominantly tropical and sub-tropical climates prevalent in India. A survey conducted among plant breeders, pathologists and entomologists shows that breeding for resistance to insect pests is at the top of the priority list of many important crops. Table 1 lists some of the important pests on major crops of India. Improvement of crop productivity by the introduction of high-yielding varieties which are more responsive to applied nitrogen and lack of proper crop rotation practices has also resulted in an enhancement of pest incidence. Insect pest management by chemicals obviously has brought about considerable protection to crop yields over the past five decades. Unfortunately, extensive and, very often, indiscriminate usage of chemical pesticides has resulted in environmental degradation, adverse effects on human health and other organisms, eradication of beneficial insects and development of pest-resistant insects. As we enter the new millennium with the objective of achieving higher and stable crop productivity to feed the burgeoning population, it is imperative to apply safe and environmentfriendly strategies to attain our goals. Insect pest management in an eco-friendly manner is no longer a dream. A large number of insecticidal molecules which are effective against insects and innocuous to man and other organisms have been reported. Tools of molecular biology and genetic engineering can facilitate harnessing and deployment of these molecules in crop plants in a safe and sustainable fashion. In this article, we review the efficacy of various categories of insecticidal proteins for the development of insect-resistant transgenic plants and discuss the prospects of large-scale cultivation of such transgenic crops in India.

Reactivation of Himalayan Frontal Fault: Implications

Abstract: Youngest of the five terrane-defining faults, the Himalayan Frontal Fault (HFF) is a series of reverse faults that demarcates the boundary of the Siwalik front of the Himalayan province with the alluvial expanse of the Indo-Gangetic Plains. Originated about 1.6 million years ago, it has truncated and attenuated the Siwalik domain. Over large tracts, it is either concealed under younger sediments or has as yet not reached the ground surface and is therefore a blind fault. The nature of this frontal fault varies along its length. Where the hidden ridges of the Indo-Gangetic basement impinge the Himalaya, the mountain front is ruptured and the HFF is repeatedly reactivated. In the sectors intervening these ridges, it is not expressed on the surface, but the ground of the adjoining Indo-Gangetic Plain is sinking, the rivers are shifting their courses and a large tract of the land is waterlogged and characterized by marshes or ponds and by strong seismicity. The northern part of the Indo-Gangetic Plains in the proximity of the ruptured mountain front is also experiencing buildup of tectonic stress. The HFF traces the frontal line of the detachment plane along which the Indian plate is sliding under the Himalaya and generating earthquakes.

Assessment of community-based restoration of Pichavaram mangrove wetland using remote sensing data

Abstract: The impact of restoration of the degraded areas of Pichavaram mangrove wetland was analysed by comparing TM digital data of 1986 (before restoration) and LISS III digital data of 2002 (after restoration). The analysis indicates that the area of the mangrove forest cover has increased by about 90%. A science-based, community-centred and process-oriented approach followed for the restoration of the Pichavaram mangrove wetland in collaboration with the Forest Department, Government of Tamil Nadu and participation of local mangrove user-communities is mainly responsible for success of the effort. This study indicates that remote sensing data can be used as a monitoring tool to assess the effectiveness of restoration and conservation programmes of the mangrove wetland, where direct and regular physical monitoring is difficult due to marshy nature of the soil and presence of numerous tidal creeks and canals.

Chirality: A challenge for the environmental scientists

Abstract: Most of the pollutants are present in the environment as a mixture of their chiral isomers. Studies have revealed that these isomers have an enantioselective distribution, metabolism, and toxicity of these pollutants, in the light of the toxicity of their individual chiral isomers. We describe here, the different chiral isomers of common pollutants, their metabolisfii and toxicity, and methods for their separation and quantification.