eChapters

1. Introduction

The study of systematics and genetic diversity between or within different species, populations, and individuals is a central task for many disciplines of biological sciences. Systematic studies can indicate which genomes in the plant kingdom to search, sample, and study for the answers to questions relating to the evolution of chemical and physical structures and their synthesis or ontogeny as well as questions about the kinship of the individuals. Such studies would help find new and useful genes and provide information about the phylogenetic relationships among crop species and their wild relatives. The application of molecular markers has been the most active area of research in both animal and plant systematics. The analysis of the genetic variability within and among populations of the species is crucial for understanding their future maintenance and developing improvement as well as conservation programs.

Classical phenotypic characters, such as morphological traits, are still extremely useful but they can sometimes be influenced by environmental conditions. Therefore, during the past decade, classical strategies of evaluating genetic variability such as comparative anatomy, morphology, embryology and physiology have been increasingly complemented by molecular techniques. These include the analysis of chemical constituents (e.g., plant secondary metabolites) and, most importantly, the characterization of macromolecules. The development of molecular markers, which are based on polymorphisms found in proteins or DNA, has greatly facilitated research in a variety of disciplines such as taxonomy, phylogeny, ecology, genetics, and plant breeding (Weising et al. 1995). The greater utility of molecular markers derives from following five inherent properties that distinguish them from morphological markers.

1. Introduction

Seeds have complex and remarkable diversity in shape, size, colour and morphological and anatomical sculpturing details of seed coat, which are valuable for taxonomic significance and can be used as an additional parameter combined with other parameters during taxa identification and classification. Distinctive seed coat morphology usually allowing identification of species even solely on the basis of seed characters. All members of a particular taxon possess variation within acceptable limits of their description and can be used for identification purposes. High structural diversity provides most valuable criteria for classification between species and family level. Takhtajan (1959) pointed out that even for the phylogenetic correlation between families and genera, the structure of the seed coat might be important. Most taxonomists agree that data concerning the structure and microstructure are of great significance mainly for the classification of angiosperm taxa. Consequently, in addition to vegetative and reproductive characters, seed characters are being used in most of the studies for the analysis of taxonomic relationship in wide variety of plant families. It was observed that seed morphology and anatomical features are rather conservatives, which makes them taxonomically important (Esau 1977; Barthlott 1984).

Gaertner (1788-1805) was the first botanist to use seeds and fruit morphology for comparison and identification of different taxa. Later on, Harz (1885) presented a comprehensive account of seed structures and their individual characters of different taxa. In the 20^th century interest in legume seed morphology was renewed. Capitaine (1912) studied the seed morphology of entire family and concluded that seed morphological characters are helpful in legume classification and identification at the tribal, generic and specific levels. After 40 years of Capitaine, Jensen (1998) documented 27 publications on seed morphology. Gunn (1981) summerized the seed characteristics for 510 legume genera. Seed characters of seventeen families were compared by Isley (1947). Duke (1961) indicated that seed shape, sculpturing and colour provide a critical indication of the systematic position of species of Drymaria (Caryophyllaceae). Obermeyer (1962) pointed out that the only reliable distinction between the two genera Chlorophytum and Anthericum of Liliaceae appears the number and shape of seeds. Hairy outgrowth on the testa, their length and colour provide useful characters in the distinction of genera/species in Malvaceae, Convolvulaceae, Asclepiadaceae and Acanthaceae. Gunn (1970, 1971) divided one hundred species of Vicia into major and minor groups on the basis of seed size, shape and length of the hilum, lens position and seed coat pattern and sculpturing. He successfully employed these characters up to specific level. Gunn and Gaffney (1974) studied the seeds of 42 economically important taxa of Solanaceae, including hilum and surface pattern as key character. Later on Gunn and Barnes (1977) had also used seed characters in the delimitation of Erythrina species. Seavey et al. (1977) studied the seeds of 210 species of Onagraceae, where seven seed groups were recognized and their evolutionary implications were also discussed. Matthews and Levinus (1986) demonstrated fairly constant seed characters in those species of Portulacaceae which have restricted geographical distribution, whereas the seeds of species with wider geographical distribution show varied morphological structures.

1. Introduction

Among the various well associated morphological units in plants, the reproductive units demand maximum protection which is achieved in pollen grains (also in spores) by encasing the germplasm with a well organized wall with a unique structure and ornamentation. Apart from its functional significance, the wall bears important characteristics which are of immense diagnostic and phylogenetic values. The morphological diversities in pollen and spore organization are greatly exemplified in the vascular plants. The term ‘Palynology’ was coined by Hyde and Williams in 1944 for the science of pollen studies, which include the study of pollen as well as spores. Although some investigators tend to limit the scope of palynology to morphological investigations but others include pollen analyses of peats, coals, honey, and rocks as well as the resulting conclusions drawn from this information, and in a wider sense it is also connected with the pollen chemistry.

The wall of pollen and spores is a very peculiar substance which is resistant to the destructive action of corrosive acids and alkalis and is readily preserved in nature under suitable conditions. The shape, size, and ornamentation or sculpturing of pollen has been the subject of study since the invention of the microscope. Pollen morphology is therefore greatly utilized in interpretation of ancient floras, for determining authentic species phylogeny, distribution and climatic conditions under which they grew, based upon the pollen content of the matrices. Pollen which lodges in moss tufts and lichen mats, or falls in water and gradually sink, or those that fall on sphagnum and clays particularly under anaerobic conditions, are well preserved. This pollen is not destroyed in the transformation of peats to lignite or clay in shale and thus has been preserved for hundreds of thousands of years.

During the present century pollen morphological studies are substantiated and elaborated magnanimously with the aid of Electron microscopy. The surface configuration and finer details are being accurately analyzed for their proper application in plant taxonomy as well as in microfossil diagnosis.

1. Introduction

Plant taxonomy and the cultivated plants have a close relationship of great antiquity. This ancient relationship can be traced back to the invention of incipient agriculture (neolithic revolution), about 10-13000 years BCE (Stearn 1965; Balter 2007). The early foundation of plant taxonomy was thus laid largely on humans’ knowledge on cultivated plants. This body of rudimentary knowledge on identifying the properties of different types of plants for food, medicine, clothing, shelter, and other uses led to the development of plant taxonomy- the first aspect of plant science to emerge as botany (Constance 1957). The fundamental principles of modern plant taxonomy with regard to the natural vegetation and flora were originally derived from cultivated plants (Li 1974).

The active process of cultivation of a plant, primarily through the intentional activity of humans has been considered the main criterion for categorising cultivated plants (Mansfeld 1959). According to Mansfeld’s approach, the number of cultivated plant species of the world was estimated to be about 7000 species, excluding partly the forestry plants, ornamentals, and plants used in amenity horticulture (Henelt and IPK 2001). Khoshbakht and Hammer (2008) expanded this list to include a total of 35000 species of cultivated plants, including 28000 ornamental plant species connected to gardening and landscaping. About 2500 plant species have undergone domestication worldwide, with over 160 families contributing one or more crop species (Zeven and de Wet 1982; Dirzo and Raven 2003).The growing numbers of cultivated plant species and the enormous diversity found in each of these species offer plenty of challenges as well as opportunities to the taxonomists to take up cultivated plant taxonomy as an active scientific pursuit. Despite this, there has been a lack of interest among taxonomists towards cultivated plant taxonomy.

1. Introduction

The scientific naming of plants is called botanical nomenclature. Although, nomenclature is included in taxonomy, but it distinctly differs from taxonomy. Plant taxonomy is concerned with grouping and classifying plants, however, the botanical nomenclature provides names for the results of this process. Names are a means of reference to all living and non-living things. The common names of pants and animals vary from place to place and language to language. But, scientific names of plants and animals are universal. For uniformity and consistency, the scientific names are given to plants according to certain internationally accepted rules provided in International Code of Nomenclature. It was Linnaeus who for the first time proposed some rules for generic names of plants in his Fundamenta Botanica, 1736 and Critica Botanica, 1737. However, the first proper set of rules of plant nomenclature was drafted by A. P. de Candolle and passed by the International Botanical Congress at Paris in 1867. The present Botanical nomenclature is governed by the International Code of Nomenclature for algae, fungi, and plants (ICN), which replaces the International Code of Botanical Nomenclature (ICBN) in 2012.

Botanical nomenclature has a long history, going back to the period when Latin was the scientific language throughout Europe, and perhaps further back to Theophrastus. The starting point for modern botanical nomenclature is Linnaeus’ Species Plantarum (1753). In the nineteenth century it became increasingly clear that there was a need for rules to govern scientific nomenclature and initiatives were taken to produce a body of laws. These rules were published in successively more sophisticated editions after every six years. The most recent is the Melbourne Code, adopted in 2012.

All formal botanical names are governed by the ICN, and within the limits set by that code there is another set of rules, the International Code of Nomenclature for Cultivated Plants (ICNCP). The latter Code applies to plant cultivars that have been deliberately altered or selected by humans and require separate recognition

1. Introduction

The increasing size and activities of humans have mounted severe pressure on the survival of other life forms on the earth. This is a matter of great concern for the humanity. Therefore, a critical study to inventory all plant species has become very essential and urgent before they are lost or become extinct. In the face of extinction of many of these species, we need to learn as much about them as quickly as possible. In the recent years there has been a great concern for biological diversity and conservation of biological resources. Although much emphasis has been given to the ways and means for inventories (Flora) of biological diversity, there is also need for more in depth studies that deal with basic relationship of species. Monographic, revisionary and systematic studies that provide basic descriptive information about organisms and their relationship are required to document the information and knowledge about the plant wealth of a country. This chapter is to highlights the usefulness of the Flora and revisionary studies, and provides the relevant information to the beginners and the budding plant taxonomists about the preparation of an ‘Ideal Flora’ and ‘Creative Revision’ to meet the requirement of the present time.

1. Introduction

Herbarium is simply a dried and pressed collection of plants arranged in an accepted sequence of classification (Lawrence 1951, Shetler 1969). It can be a very useful teaching aid or an absorbing hobby (Cronquist 1966). According to Fosberg and Sachet (1965) “A modern herbarium is a great filing system for information about plants, both primarily in the form of actual specimens of plants and secondarily in the form of published information, pictures and recorded notes”. It is also a research, training and service institution that serves as a reference centre, documentation facility and data store house (Radford 1986). It is now well recognized that a herbarium is a vast reservoir of facts about plants. The word ‘Herbarium’ was originally applied, not to a collection of plants but to a book dealing with medicinal herbs. Tournefort in about 1700 used the term as an equivalent to ‘Hortus Siccus’ which was later on adopted by Linnaeus (Stearn 1957). The present concept and development of herbarium is due to efforts of botanists for more than four centuries. The concept of herbarium has been changing continuously, which in turn, has affected the gradual development of herbarium and herbarium practices.

For practical reasons, the classification of the world’s flora is primarily based on herbarium material and the literature associated with it. Despite its limitations, a herbarium has certain advantages over living collections. It is usually only in the herbarium that we can compare all the related species of a genus in the same place, in the same state and at the same time (Davis 1961).

The herbarium material, therefore, formed the foundation of all botanical studies. We should, therefore, realise that herbaria are the custodians of enormous data pertaining to plants. They are usually seen as old-fashioned and expensive “stamp collection” without realising their paramount role in biological sciences. However, the world-wide rise of interest in the field of conservation, biodiversity and bioprospection offer a new chance for herbaria. Furthermore, computers offer a golden opportunity to raise the status of herbarium taxonomy by making routine curatorial procedures more efficient.

Although Jain and Rao (1976) elaborately discussed the methods of field collections, identification and preservation in the herbarium, the salient features of herbarium in up dated form with various procedures followed in Indian context are discussed in this chapter.

1. Introduction

Among three major functions identification, classification and nomenclature of taxonomy (Fig. 1), identification is a core activity and one of the major objectives of taxonomy, which determines whether other two elements are the same or different. Classification and nomenclature are two separate methods in taxonomy, however, both are totally dependent on the correct identification of the objects. The identification of an unidentified plant with a correctly identified specimen also involves classification. So, both identification and classification, involve comparison and judgment of similarities and differences. Therefore, the identification is a primary function in classification involving nomenclature which performs an essential role as a means of communication. According to Blackwelder (1967) “identification enables us to retrieve the appropriate facts from the system (classification) to be associated with some specimen at hand” and is “better described as the recovery side of taxonomy.” The identification of plants is very important for proper assessment and characterization of biodiversity on which the whole life of human beings is dependent starting from birth to death. The use of biodiversity for various purposes like food, nutrition, pharmacognosy etc. requires accurate and reliable identification and naming of plants (Nesbitt et al. 2010).

1. Introduction

The gymnosperms constitute a distinct subdivision of spermatophytes, the seed bearing plants. The term ‘gymnosperm’ is derived from Greek words, gymnos, naked and sperma, seed, which indicates that these are naked-seeded plants, i.e., those in which the seeds are not enclosed within the fruits but are borne freely exposed on an open carpel. In contrast in the angiosperms the seeds are enclosed within a closed carpel (ovary). The first known use of the term gymnosperm was given by Theophrastus in 300 BC in his book “Enquiry into Plants” to describe “plants with unprotected seeds”. Goebel (1905) rightly described gymnosperms as “Phanerogams without ovary”. The Scottish botanist, Robert Brown in 1825 first distinguished gymnosperms from angiosperms. At one time they were considered to be single class of seed plants, called Gymnospermae, but taxonomists are now tend to recognise four distinct divisions of extant gymnospermous plants - coniferophyta (Pinophyta), Cycadophyta, Ginkgophyta and Gnetophyta. Geological history reveals that all divisions of gymnosperms have been distinct groups since their origin.

Among the gymnosperms are plants with stems that may barely project above the ground and others develop into the largest trees on the earth. The extant gymnosperms are a small group of plants comprising ca. 1026 species belonging to 83 genera and 12 families (Christenhusz et al. 2011). They are distributed throughout the world, with extensive latitudinal and longitudinal ranges. Economically, gymnosperms are of outstanding value, fulfilling the greater proportion of our timber as well as resin requirements. They are also the dominant forest makers of the world and in addition they play a leading role in the preservation of the environment (Sahni 1990). By far the largest group of living gymnosperms is the conifers (pines, cypresses and relatives), followed by cycads and Gnetales (Gnetum, Ephedra and Welwitschia).

1. Introduction

Pteridophytes consist of ferns and their allies and are one of the oldest groups of plants on the earth, and they are commonly known as vascular cryptogams. Pteridophytes have a long history of evolution and were the dominant group of plants during the carboniferous period. The ferns, which constitute major element of the pteridophytes, preferentially grow in shade, moist habitats with moderate temperature but also occur throughout from high altitude in arctic-alpine to rain forests of tropic regions of the world. The most favoured habitat of these plants, however, is tropical mesic environment, where 65% of the living species of fernsthrive vigorously and grow luxuriantly (Page, 1979). Ferns are distinct in having rhizomes, stipes, fronds and are homosporous, whereas the fern allies exhibit scale like leaves and are heterosporous (mega and micro). In ferns, the spore matures into gametophyte that bears both male and female gametangia in a definite pattern. In fern allies, both the mega and microspore mature into female and male gametophyte that bears female and male gametangia, respectively. Pteridophytes are unique in having two different phases-the gametophyte and sporophyte. There has been a wide range of variation in spatial distribution, habitat, growth pattern and morphology of pteridophytes. Fern and fern allies, are comprised of six distantly related classes viz. Lycopodiopsida, Selaginellopsida, Isoetopsida, Equisetopsida, Psiloptopsida and Polypodiopsida (Copeland 1947; Pichi Sermoli 1987).

There are about 12000 species of the pteridophytes belonging to 300 genera in the world, whereas India is represented by about 1200 species (Chandra, 2000). Beddome (1892) during the first quarter of the twentieth century provided a comprehensive account on ferns of British India, and subsequently, Clarke (1880) and Hope (1899, 1900, 1902, 1903, 1904) made significant contributions in taxonomic studies of pteridophytes mainly the ferns of north western India. Several workers (Nayar and Kaur 1974; Dixit 1984; Chandra and Kaur 1987, 1994; Manickam et al. 1992; Khullar 1994, 2000; Chandra 2000; Singh 2003; Singh and Panigrahi 2005a, 2005b) have significantly contributed towards the taxonomy of Indian pteridophytes.

1. Introduction

Bryophytes are atracheate, archegoniate non-flowering group of highly diversified plants. Among plants they form the second largest group comprising of 15000 – 25,000 species (Gradstein et al. 2001, Crum 2001). They occur in every continent on globe, in every location habitable by photosynthetic plants and grow luxuriantly between altitude of 1000-3500m. In India, nearly 850 species of liverworts, 41 species of hornworts and 2000 species of mosses, such as are known so far (Singh 1997, Vohra and Aziz 1997). These plants exhibit a variable range of size as some of them are only 0.5-2 mm in size, while on the other end mosses Polytrichum commune and Dawsonia superba can attain a height of 50 and 70 cm, respectively. These plants play a vital role in soil conservation and formation of fertile substrata for other plants in forest ecosystem. On account of unique moisture retaining capacity, Sphagnum and other pleurocarpous mosses are being used as mulching substances, moss grass, moss sticks and bags in horticulture industry. These plants are very sensitive to environmental pollution due to simple structure and devoid of cuticle, and accumulate heavy metals too, hence serve as good bio-monitor of pollution. Some novel compounds viz., marchantin, riccardin, lunularic acid, terpenes and other phenolic compounds have been detected in several thalloid as well as leafy liverworts.

Bryophytes exhibit heteromorphic alternation of generations in which the gametophytic phase (haploid phase) is a prominent and nutritionally self- sufficient independent phase in the life cycle while the sporophyte (diploid phase) is attached and dependent on the gametophyte. The main plant body (Gametophyte) is either thalloid or leafy (differentiated into axis and leaves). They are attached to substratum by simple hair like structures called as rhizoids. The rhizoids are usually unicellular, simple (smooth walled) in hornworts; simple, tuberculate or sinuate in liverworts or multicellular, oblique septate in mosses. Sex organs, antheridia and archegonia produce antherozoids and eggs respectively. After fertilization the zygote is formed which develops into the sporophyte. The sporophyte consists of foot, seta and capsule. The foot is embedded in the gametophytic tissue and draws nourishment for the development of sporophyte. Seta is generally stalk like may be of variable length which holds the capsule. The capsule is the main fertile portion of the sporophytic generation. The spore mother cells, after meiotic division, form spore tetrads having haploid spores. The elater mother cells form elaters, which are sterile and help in the dispersal of spores. Bryophytes are homosporous. Spores germinate to form young gametophyte in liverworts and hornworts, while in mosses, spores first give rise to protonema then buds develop on the protonema to form new gametophytes.

1. Introduction

The objective of algal taxonomic collections is to represent the natural population, flora and diversity in size and form. Therefore, it is important to collect the representative samples seasonally from various habitats. Collection of information about the habitats and other details are also very important. For algal sampling the first thing to consider is how to collect the specimens. The freshwater algae show an ability to tolerate a wide range of environmental condition. Under natural conditions, they usually grow in mixed communities which may include many species and genera. Field study provides information about the site, environment, season and size and shape of the living algal thallus in its natural surroundings. Many algae can be tentatively identified by their appearance, shape and colour of thallus in a particular habitat. Algal population can be sampled in a number of different ways, depending on the nature of the habitat and the location of the algae within the water body. The specimens must be prepared carefully so that important morphological characters are displayed as fully and completely for further researches.

1. Introduction

India, as a party to the Convention on Biological Diversity (CBD), has obliged to document a whole range of organism diversity within her territorial boundaries, make all attempts to conserve these bio-resources and monitor the efficacy of the conservation measures adopted. With its diverse ecological conditions and unique geographical location, Indian landmass supports rich diversity of algal flora. However, this algal wealth needs to be systematically surveyed and documented from all possible habitats. Ecological patterns emerged from recent studies within India are assessed with the identification of knowledge gaps and conservation implications in algal systematics.

During last one decade, great advances have been made in the field of Algology/Phycology throughout the world. Over the years algae has attained a greater reputation and popularity because of its economic importance, particularly as food, for commercial products, water contamination, toxin production, sewage oxidation, municipal water purification in fisheries and above all for the study of fundamental scientific information. But before the algae put in to such important use, it is imperative to have a baseline data about the material in question. Without knowing the status of algal resources of any area one cannot have projections for their utilization or gain knowledge of their ecological role and functions. The taxonomy of algae is, therefore, a prerequisite for all applied fields of algae apart from academic interest. Recent global surveys have revealed that there is lack of knowledge about fresh water algal diversity of tropical countries including India.

1. Introduction

The word ‘lichen’ has a Greek origin, which was referred to the superficial growth of fungus like organism on the bark of olive trees. Theophrastus, the Father of Botany coined the term ‘lichen’ during 300 BC and introduced this group of plants to the scientific world.

Lichen is a combination of two organisms, an alga and a fungus, living together in symbiotic association. Sometimes instead of an alga a cyanobacterium (blue-green alga) may be present in the lichen thallus. The algal component in the lichen is generally called as ‘photobiont’ as it contains photosynthetic pigment. The fungal part is called as ‘mycobiont’ (myco = fungus). The photobiont and the mycobiont loose their original identity in symbiotic association and the resulting organism is the lichen which behaves as a single organism, both morphologically and physiologically. Hence, the lichen is called as a composite organism. The lichen thallus is made 90% of mycobiont which provides shape, structure and colour to the lichen. In a lichen thallus whatever visible from outside is fungal part, which holds algae inside its body (Fig. 1) and therefore, the lichens are placed within the Kingdom - Fungi. The fungi present in lichens are called as ‘lichenized fungi’. Among the 20,000 lichen species present in the world, 98.9% of them belongs to Ascomycetes group while Bacidiomycetes and Deuteriomycetes groups are represented by only 0.1% and 1%, respectively.

1. Introduction

Lichens are the most fascinating and widely distributed organisms on earth. The lichens are unique in having two microorganism in a single plant- a phycobiont (alga) and a mycobiont (fungus) forming a thallus that does not resemble either symbionts in the free living (non- lichenized) state. By virtue of the peculiar structure and physiology, lichens have high tolerance of drought and cold and are able to grow in the diverse geographical regions from icy expanses to tropical and subtropical parts and from drier, hot deserts to moist humid climate. Lichens grow on any substratum that provides a convenient foot hold to them. This may be soil (terricolous), humus (humicolous), stones, rocks, brick (saxicolous), lime plaster (calcicolous), leaves (folicolous), tree trunk (corticolous), decaying wood (lignicolous) and other man made substratum like iron pipes, asbestos sheet and glass panes. Sometimes lichens also grow on some insects and animals. Lichens which are bigger in size and shape can be easily recognized as leaf like (foliose) and thread like (fruticose) (commonly called macrolichens), while those which forming a crust over the substratum and quite smaller in size are categorized under microlichens.

Apart from altitudinal variation, the vegetation and forest types of higher plants also play an important role in determining the type of lichen flora of the region. Based on the forest types six lichen vegetation zones are known in India such as: Moist tropical evergreen forest, Cold deserts in the Himalayas, South Peninsular region, Mid Eastern Indian & Peninsular Plateau, Dry and arid regions and Indo-gangetic plains of central India, Coastal regions of India and Andaman & Nicobar Islands. The cold deserts in the Himalayas exhibit some unique group of lichens having restricted distribution only in such habitats.

1. Introduction

Fungi are ubiquitously present in air, water, soil and organisms, or on organism surfaces. They are a group of eukaryotic system that are of great applied and scientific interest to common man, microbiologists, agriculturists and industrialists. They are a diverse group of organisms with respect to taxonomy, size, morphological appearance, mode of nutrition and reproduction. Fungi are eukaryotic spore bearing protists that lack chlorophyll. Fungi comprise the molds and yeasts. Yeasts are usually unicellular measuring only several microns in diameter, whereas molds are filamentous and multicellular which may grow up to several meters in diameter like the extremely large polypores. Fungi generally reproduce both sexually and asexually (Gow and Gadd 1995).

Although it is not easy to define fungi, biologists currently use the term “Fungus” to include nucleated, spore bearing, achlorophyllous organisms with absorptive nutrition which generally reproduce sexually and asexually, and whose filamentous branched somatic structures are typically surrounded by cell walls containing cellulose of chitin or both. A feature which all fungi have in common is their mode of nutrition. Like animals, fungi are heterotrophic organisms, which must consume preformed organic matter. They may live as saprophyte or parasites. They are of great economic importance to man and play an important role in the disintegration of organic matter and affect us directly by destroying food, fabric, leather and other commercial goods. They are responsible for a large number of diseases of plants, animals and man.

1. Introduction

Viruses are a unique group of infectious agents. They are distinct in their simple, acellular organization; however, they are the connecting link between live and dead. Viruses are also the perfect example of obligate intracellular parasitism. Despite their simplicity, plant viruses are extremely important and drawn attention of researches because they can be used as model to study the disease establishment and progression mechanism, reproduction inside the host and trilateral host-virus-vector relationships. Their small genome also gave liberty to extensively understand the genome evolution caused by the genetic exchange or recombination. As a consequence, this will help in the development of facile methods for management and control of new emerging viruses and their strains.

This chapter is written for the beginners and students of virology subject to provide the fundamental knowledge about the origin, history of plant virology, the general features of plant viruses, their structure, shape and size, mode of spread and development of their management strategies. Besides this, the new development of non-conventional methods for developing virus-resistance in plants has also been explained for enhancing the quality and production of commercial crops in the country.

1. Introduction

Microbial diversity is becoming increasingly essential with the requirement to preserve the integrity, function and long-term sustainability of natural and managed ecosystems. However, our knowledge of the diversity of microbes remains obscure due to lack of appropriate approaches to evaluate the contribution of different components of the soil microbes to ecosystem. This lack of approaches together with the complex and heterogeneous matrix that soil microbes are embedded in, poses great challenges to understand the dynamics of microbial communities in soils (Nautiyal et al. 2010; Chauhan et al. 2013).

In classical terms, diversity is described as the total number of species present, i.e. species richness or species abundance, and the distribution of individuals among those species i.e. species evenness or species equitability. However, the incorporation of these two components into diversity indices has led to much controversy among ecologists (Atlas 1984). The Shannon-Weaver index (Shannon and Weaver 1949) is probably the most widely used index for measuring diversity of a microbial community. But this index, as many others that have been proposed, has its own limitations. A major difficulty is that both richness and evenness play a role in determining the value of the index. Therefore, any diversity index is a single value and thus cannot indicate the total make-up of a community. It is recommended that evenness, richness and diversity values should be calculated in order to obtain an objective assessment of community structure (Atlas 1984). From molecular point of view, diversity often refers to the number of different sequence type present in a habitat e.g. a soil (Ogram 2000). Measuring this type of diversity does not give information about the frequency of individual species, but it can give valuable information about changes in the community structure and species richness in response to changes in the physico-chemical properties of the soil and soil management practices (Nautiyal et al. 2010).

ABSTRACT

The genus Aconitum is in the limelight of the current scenario of the pharmacopeia and has became the centre of attention in the field of herbal medicines, as is manifested with various biological and pharmacological cores which make the genus most imperative. For vast decades some species of the genus Aconitum and its derivatives were considered as vizulently fatal but were liquidated as intact drug elites through traditional as well as modern system of medicine. The retrospection of the validated information in account of the genus Aconitum represent a pioneering approach to corroborate the scientific studies on almost everyaspect of the herbal genusAconitum, as a number of species belonging to this genus has been enlisted in the Red Data Book of IUCN which have been renowned for their medicinal benefits in various systems of medicine. The tubers some species of Aconitum contain lethal diterpene alkaloids such as aconitine, mesaconitine, and hypaconitine, which easily can be directed into screened harmless alkaloids such as benzoylaconine, aconine, and pyroaconine by heating or alkaline treatment. Currently, the processed tubers are widely and safely practiced for the remedyof pain, neuronal disorders, inflammation, and rheumatism and have a huge therapeutic index for curing ailments like hysteria, throat infection, dyspepsia, abdominal pain, diabetes and also as a cardiac depressant in massive arterial tension of cardiac origin. An important component extracted from some species of Aconitum, Lycaconitine has been found to be effective against multi-drug resistant cancers. The di-terpenoid alkaloids of aconite source and their increasing demand for the active compounds used in different systems of medicine has led to overharvesting of the tubers, resulting in rapid depletion of the natural stocks of this valuable plant. As a consequence, the genus is now on the list of rare and threatened species. Since the commercial demand of this important medicinal plant is very high and hence needs to be conserved as the species density of this genus has been threatned due to many factors. As such diverse efficient and standardized protocols for its regeneration like micropropagation, somatic embryogenesis and some other conventional efforts like storage of seeds as a means of ex-situ conservation must be attributed on the aspects of conservationof genusAconitum. The exploitation of population genetic diversity will provide useful information for the biological conservation of these esteemed species of Aconitum in the regions . Since a complete revision of the genus Aconitum in the region has not yet been carried out and the high level of endemism and a lack of relevant information of the genus Aconitum have made its various scientific studies a very interesting object. The scientific and systematic information about the genus Aconitum generated demands validation as only a little attention has been done on its various aspects from cultivation, conservation, phytochemistry and pharmacological evaluation to the molecular characterization. Consequently species specific measures are needed and a lot of important attributes has to be assigned to the species of this genus which will ultimately help to ensure simultaneously both conservation as well as sustainability in raw material production of the genus.

ABSTRACT

Systematic studies through stored specimens in herbaria and museum of defined geographical areas provide a set of baseline data for understanding the vegetation composition of a defined ecosyetm. A stored plant collection in herbaria offers a rich portrait of biodiversity, making innumerable contribution to science and human society. Digitization coupled with hosting of such information on world wide web (www) system has been accepted as an important tool for the dissemination of the botanical specimens in the form of databasing, imaging and geo-referencing of voucher specimens. In the present communication, we describe the development of the Janaki Ammal Herbarium (JAH) database that contains a comprehensive and searchable data of voucher snaps, historical background and statistical analysis of 23,225 voucher specimens. The information on JAH database is easy to extract data on botanical names, author citation, variety (if any), family, collection number, specific location, collection date, habitat, collector’s name and remarks on morphology. The goal of the present investigation is to digitize (database, image, georeference) all specimensin JAH, enabling themto be made available through a single portal. At concluding, all vouchers of JAH made publicly accessible via world wide web user interfaces, and also linked to PubMed, NCBI Taxonomy, where the site provide information related to Entrez records, comments and references of the particular species, while Wiki species site is linked to the free species directory. It also provide link of online accessible herbarium-based databases of the world.