eChapters

Introduction

Advances in pesticide were measured exclusively by the assessment of its efficacy in management alone. But today food production has ceased to be a major concern, due to stable increase in population levels and success of innovative agricultural technologies. At this juncture, the agrochemical industry that primarily recognized the farmers as their customers has failed to acknowledge the public as an important client. Perception of the public reflects that, the negative aspects of pesticides seem to outnumber their benefits. The increased reflection on environmental concern over pesticide use has been instrumental in a large upsurge of biological disease control. Development of fungicide resistance among the pathogens, ground water and foodstuff pollution and the development of oncogenic risks has further encouraged for the exploitation of antagonistic microflora in disease management.

Biological control of plant pathogens can be broadly defined as the reduction of inoculum density or disease producing activities of a pathogen or parasite in its active or dormant state by one or more organisms, accomplished naturally or through manipulation of environment, host or antagonist or by mass introduction of one or more antagonists. The decades of laboratory experiments have led to the explosion in the field of bio-control and introduced more than 50 commercial formulations comprising of fungi and bacteria. To have a successful management of plant diseases and to have a pollution free environment, the biocontrol agents has to be ensured for its availability for commercial use by the end users. To harness the potential of biopesticides by the stakeholders and end users the product has to be registered under Central Insecticide Board authorities concerned of the respective countries.

Introduction

A sustainable approach to managing pests by combining biological, cultural, physical and chemical tools in a way that minimizes economic, health and environmental risks. The objective for IPM practitioners is to minimize risks to human health and the environment from the pest management actions implemented. IPM is a holistic approach that seeks to manage pests by using methods that are effective, economically sound, and ecologically compatible. IPM practitioners base decisions on information that is collected systematically as they integrate economic, environmental, and social goals. IPM promotes the use and integration of biological control agent as one of the strategies for pest and disease management. Because, biological control of plant pathogen is a potential alternative to the use of environment harming chemical pesticides in agriculture.

To study the characteristics of microorganisms, it is essential to culture and growth them. Growth is the increase in cell number which can be obtained by providing proper physical and chemical conditions. Medium is a substance that provides nutrients for growth and multiplication of microorganisms. Any medium for the cultivation of bacteria and fungi must provide certain basic nutritional requirements which include a carbon, nitrogen, phosphate and various mineral nutrients. The following is the medium composition for the isolation and culturing of different biocontrol agents

The isolation of microbes is commonly done using serial dilution technique.

1. Trichoderma

Trichoderma is one of the important biocontrol agents. The colonies first produce mycelial growth and then turn yellow and finally produce a dark green color mat.

The discovery and use of synthetic chemicals has contributed greatly to the increase of food production industry by controlling pest and diseases. However, the use of synthetic chemicals has raised number of ecological problems apart from increasing the cost of cultivation. In recent years, scientists have directed their attention in exploring the potential of beneficial microbes for plant protection measures. Biocontrol agents exhibit antagonistic activity against plant pathogens and activate resistance mechanisms in the host despite improving plant growth. In agricultural soils the nutritional condition is depleted hence beneficial microbes decrease and increase the pathogenic microbes. To ensure the sustained availability of biocontrol agents mass production technique and formulation development protocols has to be standardized which also increases the shelf life of the formulation. Though these agents have a very good potential in the management of Pest and Diseases it can not be used as cell suspension under field conditions. The cell suspensions of these biocontrol agents should be immobilized in certain carriers and should be prepared as formulations. The organic carriers used for formulation development include peat, turf, talc, lignite, kaolinite, pyrophylite, zeolite, alginate, pressmud, sawdust, vermiculate, etc.

Bacteria are by far the common type of soil microorganisms, possibly because they can grow rapidly and have the ability to utilize a wide range of substances as either carbon or nitrogen sources. The bacteria that provide some benefit to plants are found near, on (or) even within the roots of plants (Kloepper et al., 1980) to protect the plants from pathogen attack called as antagonistic organism. Among the many potential bacterial antagonists associated with the plant roots the fluorescent pseudomonads have received prominent attention due to their abundance in plant rhizosphere and their ability to colonize roots of a wide range of crop plants. Pseudomonas fluorescens is a Gram negative, non spore forming, rod shaped bacteria producing pigments which are greenish, fluorescent and water soluble. It is found to be effective against the following fungal pathogens viz., Rhizoctonia solani, Macrophomina phaseolina, Fusarium udum, Pyricularia grisea, Fusarium oxysporum fsp. cubense. It is capable of surviving in the spermosphere, rhizosphere and phyllosphere of plants. The mechanisms of biological action exhibited inovles antibiosis, competition, lysis and induced resistance. Pseudomonas have an exceptional capacity to produce a wide variety of metabolites, including antibiotics, that are toxic to plant pathogens.

1. Raw Materials

Culture of Bacillus subtilis

Talc powder - 300 mesh

Shelf life for Pseudomonas fluorescens (TNAU Pf-1)

Aim: To find out the shelf life of P. fluorescens (TNAU Pf-1) using different carrier materials

Product: The talc based P. fluorescens (TNAU Pf-1) product is used for the study on shelf life.

Selective medium (King’B medium) for Pseudomonads

Deoxyribonucleic acid (DNA) carries the genetic instruction for the biological development and functioning of all cellular forms of life. It is the blue print which contains the instructions to construct other cell components. Molecular biology experiments often require isolation of DNA for a variety of purposes like construction of DNA libraries, gene cloning, PCR and other marker technology, etc. The extraction of DNA from actively growing tissue is relatively easier yielding higher quantities of DNA.

Principle

The cell wall is ruptured and the proteins associated with DNA are removed by detergent like SDS or by interaction with phenol. Lipids are extracted with alcohol and DNA is precipitated by isopropanol.

Materials Required

Maize seed samples, Liquid nitrogen, CTAB (Cetyl trimethyl ammonium bromide), Chloroform, isoamyl alcohol, Sodium chloride, Glacial acetic acid, Isopropyl alcohol and 70% ice cold ethanol, TE buffer (5X) (24.2 g of Tris base, 5.71 ml of galcial acetic acid, 10 ml of 0.5M EDTA (pH 8.0) , dissolved in 1000 ml of distilled water). Prepare 1X TE as per the requirement.

Many Bacillus species are capable of producing a wide variety of secondary metabolites that are diverse in structure and function. The production of metabolites with antimicrobial activity is one determinant of their ability to control plant diseases. The activity is determined using PCR. PCR consists of an exponential amplification of a DNA fragment, and its principle is based on the mechanism of DNA replication in vivo. dsDNA is denatured to ssDNA, duplicated, and this process is repeated along the reaction according to the following formula

Agarose gel electrophoresis is used for the fractionation and characterization of nucleic acids. It is a simple and highly effective method for separating, identifying and purifying DNA fragments of various sizes. DNA can be checked for size, intactness, homogeneity and purity by this technique. Agarose is a purified form of agar and forms a gel by hydrogen bonding of the agarose monomers. Increasing the Agarose concentration of a gel reduces the migration speed and enables separation of smaller DNA molecules. Shorter molecules move faster and migrate further than longer ones.

Aim: To study the size of the DNA extracted from the fungal culture.

Principle: Ethidium Bromide added to the gel interacts with the bases of DNA and fluorescence orange when irradiated with UV light.

Introduction

Studies on biocontrol agents have revealed the presence of a diverse range of antifungal metabolites derived from amino acid, polyketones and isoprenoid biosynthetic pathways, each of which has distinctive regulatory points and is subjected to different stimuli within organisms. In this experiment, the extraction of secondary metabolites from the culture of T. viride and Chaetomium globosum will be demonstrated.

Entomopathogenic nematode (EPN) viz., Heterorhabditis, Neosteinernema and Steinernema have been recovered from many regions of the world. They selectively infect many insects and a few other arthropods but do not adversely affect mammals or plants. They are actually vectors of pathogenic bacteria, cause relatively rapid death of the host (24 – 48 h) and show considerable potential in biological control of insect pests in the integrated pest management systems.

EPNs are similar to insect parasitoids in that the immature form develops at the expense of one host individual; they are ecologically similar to both parasitoids and arthropod predators because the host individually killed. However, these nematodes differ from predators and parasitoids in two ways: (1) the nematode is mutualistically associated with a bacterial pathogen which actually kills the host, and (2) the pathogenicity of the bacterium has a great influence on the efficacy of the system (Ehler, 1990). The purpose of this chapter is to introduce EPN as biocontrol agents in this refresher course and to provide an overview of some current issues in biological control of insects with particular emphasis on their relevance to the use of EPNs.

Biological control is defined as the action of natural enemies which maintains a host population at levels lower than would occur in the absence of the enemies. Natural enemies will include parasitoids, predators, nematodes, microbial pathogens and their gene products. Entomologists generally divide biological control into two categories: (1) natural biological control which is effected by native or coevolved natural enemies in the native home (origin) of a given insect and (2) applied biological control which due to human intervention. Applied biological control is further divided into classical biological control (introduction of exotic natural enemies) and augmentative biological control (enhancement of natural enemies already in place).

Introduction

Corcyra cephalonica commonly called as rice meal moth or rice moth is a pest of stored foods, viz., cereals, cereal products, oilseeds, pulses, dried fruits, nuts and spices. Many of the natural enemies mass-bred in the laboratory for use in field against crop pests are dependent on either egg or larval stages of Corcyra due to the simple reason that it is easier and cheaper to produce natural enemies on different stages of Corcyra than on their original hosts.

Morphology and Biology of Corcyra

The eggs are oval and measure 0.5 x 0.3 mm. The white surface is sculptured and has a short nipple-like structure at one end. The larvae are generally creamish – white except for the head capsule and the prothoracic tergite, which are brown. There are well-developed prolegs on abdominal segments 3-6 and 10. A fully matured larva measures 15 mm. The last-instar larva spins a closely woven, very tough, double-layered cocoon in which it develops into a dark-brown pupa. The anterior portion of the cocoon has a line of weakness through which the adult emerges. The adults are small. The hind-wings are pale-buff, and the fore-wings are mid-brown or greyish-brown with thin vague lines of darker brown colour along the wing veins. The males are smaller than the females.

Sexual activity usually begins shortly after adult emergence. There is a preoviposition period of about 2 days. Egg-laying mainly occurs during the night. The greatest numbers are laid on the second and third days after emergence, although oviposition may continue throughout life. Eggs take about 2-3 days to hatch. Optimum conditions for larval development of C. cephalonica are 30 – 32.5 °C and 70 per cent RH, at which, the period from egg hatch to adult emergence is only 26-27 days. There is considerable variation in the number of larval instars; however, males generally have 7 and females have 8. The last-instar larvae pupate within the food. The adults emerge through the anterior end of the cocoon, where there is a line of weakness. The sex ratio is 1:1. The adult moth is nocturnal and is most active at nightfall.

Although the Rhabditids have been studied from last one century, the field level use of Entomopathogenic nematodes the members of Rhabditids for the management of insect pest was followed only after Dutky who practically used EPNs in 1937 on Apple Codling moth.

The taxonomy of Entomopathogenic nematodes of the order Rhabditidae is discussed in this lecture.

Basically we need to mount and prepare the slide for observation of various stages of EPN as detailed below in Table.1

I. In vivo culturing technique

In vivo culturing means culturing of entomopathogenic nematodes (EPN) in the host. Generally rice meal moth, Corcyra cephalonica and greater wax moth, Galleria mellonella are used as insect hosts for rearing EPNs.Insect hosts such as Spodoptera, Helicoverpa and Bombyx mori are also used for culturing Steinernema and Heterorhabditis but these insects need plant host especially leaves for culturing. Corcyra can be grown in broken cumbu grains and Galleria in honey comb or artificial diet.

Introduction

Entomopathogenic nematodes (EPNs) viz., Heterorhabditis, Neosteinernema and Steinernema have been recovered from many regions of the world and have been used commercially as biocontrol agents of insect pests. They are associated with mutualistic bacteria in the genus Xenorhabdus for Steinernematidae and Photorhabdus for Heterorhabditidae. The infective juvenile nematodes enter their host insect through natural openings (mouth, anus or spiracles), they release bacteria into the insect and cause rapid death of insect host (24-48 h). EPNs were used against many insect pests viz., rice leaf folder, Cnaphalocrocis medinalis (Srinivas and Prasad, 1991); tobacco cutworm, Spodoptera litura (Rajkumar et al., 2003); brinjal fruit borer, Leucinodes orbonalis (Hussaini et al., 2002) diamond back moth, Plutella xylostella (Singh and Shinde, 2002); Diaprepes abbreviates (Jenkins et al., 2007); Bemesia tabaci (QiuBaoli et al., 2008) and sugar beet beetle (Saleh et al. 2009).

Introduction

Agricultural production in India is constrained by number of biotic and abiotic factors. India is a tropical country and has a climate which is conducive for insect pests which are, one of the major constraints in agricultural production, processing and storage. Annual crop losses due to insect pests and diseases in India are estimated to be 18 percent of the agricultural output. Insect pests are widespread in all the agroclimatic zones and large quantities of insecticides are used to control these pests. Indiscriminate use of insecticides, lack of adequate knowledge on proper application techniques and dosages, and frequent use of broad spectrum insecticides are common in India. There is a need to identify suitable alternative methods for the management of insect pests and among them, biological control using viruses, bacteria, fungi and entomopathogenic nematodes is gaining greater attention world over.

Nematode families of Steinernematidae and Heterorhabditidae attracted most attention as they contain the entomopathogenic nematodes (EPN). Entomopathogenic nematodes are obligate parasites of insects that kill their hosts with the aid of bacteria (Xenorhabdus and Photorhabdus) carried in the nematode’s alimentary canal. The lethal obligate insect parasites are ubiquitously distributed without pathogenicity to mammals and beneficial non-target insects, and exempted from registration requirements. Currently there are about 98 valid EPN species belonging to Steinernema (79) and Heterorhabditis (19). Soil surveys conducted in divergent areas of Indian subcontinent have demonstrated high diversity of EPN across seasons, habitats, and geographic regions. There are several target pests in India that can be controlled with entomopathogenic nematodes and several workers have used EPN against cutworms, stem borer, white grubs, etc. under laboratory and field conditions and are compatible with existing IPM programmes.

Entomopathogenic nematodes (EPN) in the family Steinernematidae and Heterorhabditidae have enormous potential to control insect pests of economic importance. Since, chemical pesticides pose environmental hazards, these nematodes have received considerable attention as potential bio-insecticides because of their wide host spectrum, active host seeking, killing the host within 48 h, easy mass production, storage and application and are environmentally safe. One of the important criteria for a successful biocontrol agent is formulation of nematodes into a stable product, which has played a significant role in commercialization of these biological control agents. Apart from formulation field application and desired control of insect pests decides the success of EPN.

Formulation of Entomopathogenic Nematodes

EPNs have been known since 1929 but they became commercially available only during 1990s.The first attempts at formulating EPN were initiated in 1979 but the shelf life was very limited (one month). Infective juveniles carried on moist substrates such as sponge, vermiculite and peat require continuous refrigeration to maintain their viability. While formulating nematodes, two things are necessary, a long shelf-life and easy application method. The simplest method is impregnating a moist substrate (such as sponge, peat, vermiculite, etc.) with nematodes. The sponge needs to be squeezed in water before application, to release the nematodes, whereas nematodes from other carriers could be applied directly to the soil. However, these formulations are labour-intensive, require continuous refrigeration and lack economy of scale and therefore can be used on small scale only.

Although the infective juveniles of entomopathogenic nematodes can be stored for several months in water in refrigerated bubbled tank, high cost and difficulties of maintaining quality preclude the deployment of this method. Therefore, nematodes are usually formulated into solid or semi-liquid substrates soon after they are produced.

The culture of colored and attractive fish in glass aquariums for aesthetic use is called ornamental fish culture. The beautiful, tiny fishes or ornamental fishes are peaceful in nature and suitable for keeping in captivity. These lovely fishes are usually kept in a glass made aquarium and decorated with toys, plants, ceramic structures etc. for beautification. It displays the attractive fish that live in a natural environment decorated with accessories while maintaining environmental parameters in tanks/aquariums by using aerators, heaters, filters, lights to control water movement, temperature, suspended organic matter, illumination etc. besides feeding. Keeping ornamental fish in a glass tank is a very old and popular hobby. More and more people are getting attracted to this hobby and due to growing interest in aquarium keeping; it has resulted in a steady expansion in its trade in more than 125 countries. Household aquariums are more popular; therefore, less than 1% of the global market for ornamental fishes belongs to the public aquaria sector. Most of the ornamental fish is available from developing countries in the tropical and sub-tropical regions. The international trade in ornamental fish breeding and culture provides employment opportunities for thousands of rural people in developing countries. Ornamental fish is becoming an important component in Indian fisheries too, along with food fishes, for both income and employment generation. As a result of advancements in breeding, transport and rearing technology, more and more fish species are being recognized as ornamental fish almost every year. The ornamental fishery is recognized by many developing countries for employment generation and livelihoods. Ecologically suitable culture systems must be developed by evolving micro, small and medium enterprises for sustainable growth.

India is one among the top ten mega-diverse countries of the world in terms of fish diversity (Dudgeon 2003). FishBase (Froese & Pauly 2016) has listed around 917 freshwater fish species (out of 2465 total fish species) as occurring in India. According to National Fisheries Development Board, Hyderabad, inland and marine waters in India possess a rich diversity of ornamental fish, with over 195 indigenous varieties reported from North-East Region and Western Ghats, and nearly 400 fish species from marine ecosystems. There are several other fish species which qualify to be called as ornamental fish. Considering enormous and diverse indigenous fish resources of the country, there is immense scope for India to become a potential candidate and a strong competitor in the international ornamental fish trade. Government of India has recognized ornamental fish sector as one of the thrust areas for generating employment opportunities and augmenting our foreign exchange earnings. It is estimated that the sector is directly and indirectly supporting about 50,000 of house-holds mainly in rural India. Large number of freshwater ornamental fish species is recorded from Indian waters and the majority of the global trade is based on freshwater exotic ornamental fishes including both classified and non-classified types.

Design and construction of farm including management is important with the advancement of cultural practices and increased involment of people. These are some common resources for breeding, rearing and display of ornamental fish.

Small scale commercial farms

Mazla/earthen vats

These are baked earthen containers and usually round in shape. These are used to keep the gravid female of livebearer fish for breeding. Its water holding capacity is 7.5-10.0 litre.

Ornamental Plants are a real attraction to the aquarium tank. While some plants are both ornamental and functional, people usually use the term “ornamental plants” to refer to plants which have no value beyond being attractive, although many people feel that the attractive value itself is quite enough. They provide optimal habitat for the fishes especially for the fry (baby fishes). It maintains the ecosystem of the aquarium tanks by providing good oxygen, food and also acts as a good hiding place for the baby fish. Mostly all aquatic plants are very easy to grow and care. They are always good for gold fish and other similar fishes. There is a huge variety of plants. Ornamental plants are grown for decoration, rather than food or raw materials. They are most often intentionally planted for aesthetic appeal. However, ornamental plants also serve some less obvious uses such as for the purpose of fragrance, for attracting wildlife and for cleaning the air. Ornamentals encompass a wide array of plants. Commonly, ornamental plants are grown for the display of aesthetic features including: flowers, leaves, scent, overall foliage texture, fruit, stem and bark, and aesthetic form. The concept of ornamental plants is used for decorative purposes in aquariums, gardens, home gardens, landscape design projects, squares, parks etc.

Aquatic plants predominantly grow in water. They vary greatly in type, with some being quite similar to common land plants while others are quite different. Aquatic plants can be commonly classified into four types: algae, floating plants, submerged plants and emerged plants. Aquatic plants live in water. This means that they require being submersed to survive or that they can only grow and thrive in water. Many aquatic plants can tolerate being emerged, meaning they’re out of the water for short periods of time, but require immersion in water for long-term survival.

There are some plants that simply can’t tolerate being emerged at all, but this is rare. These plants can only live when fully immersed in water. Most macro- algae require total submersion in water for the span of its entire life. Most aquatic plants, however, have roots underwater but can only grow or flower in a partially emerged state. All plants, aquatic and otherwise, require sunlight, soil, gases and water to survive. Plants make their own food via the process of photosynthesis; this means that they need a source of energy to drive this biochemical process, and the sun provides a perfect one. Plants can carry on for periods without sunlight, just as animals can live on stored fuel for a while in times of need. The soil offers a place for the plant’s roots to take hold.

Air contains large amounts of the carbon dioxide gas (CO2), plants need to power photosynthesis, but aquatic plants have evolved to draw in CO₂ that is dissolved in water in relatively small amounts. Finally, plants need water to combine with the CO2 to complete photosynthesis by generating oxygen and glucose.

Feed plays a vital role not only in growth but it also enhances the market value of ornamental fish. In natural waters, fish has access to a variety of natural food items, but their overall wellbeing depends upon the availability of their favorite food. However, in a confined system, nutritionally balanced supplementary feed is indispensable due to limitation on availability of natural live fish food organisms. In general, ornamental fish are fed with a variety of commercially available pelleted feeds, imported from countries like Singapore, Hong Kong, Korea and Thailand etc. Although they are very popular among ornamental fish hobbyists, the high cost of these feeds is not economical for commercial-scale application at farmer’s level. Further, in contrast to food fish in a pond, feeding ornamental fish in smaller culture units need high precision. Therefore, it is essential for an ornamental fish producer to possess technical know-how regarding nutritional requirements and feeding behaviour of different species in order to formulate farm-made feeds by using locally available low- cost ingredients.

Formulation of low cost and nutritionally balanced supplementary feed, using locally available ingredients, is the key to the success of ornamental fish culture in India. To reduce the cost of feed and make the ornamental fish production venture more profitable, the feed can be prepared at farm by using cost-effective and locally available quality ingredients (plant/animal-based).

Identification and selection of the feed ingredients are essential and it should be according to the fish species to be cultured. A number of feed ingredients may be locally available which can be used for feed formulation. Fish culturists have to identify and choose the best ingredients, depending upon its easy availability, nutrient status and cost, keeping in mind the nutritional requirement of ornamental fish (size, feeding habits, etc.) to be cultured.

Learning about water chemistry is often neglected by most of the aquarium owners. By understanding the concepts of water chemistry, they can considerably improve success rate in rearing healthy fishes. It is well known that the quality of water has a direct impact on the health of the fish. But many aquarium owners do not understand the basic internal chemistry of the water, nor do they understand how to correct it or safely adjust it. Until the basics of water chemistry is understood and some common water maintenance techniques are learnt, it will be difficult to maintain a healthy and safe environment for the fish in tank. The water quality is by far the single most important factor for the healthy fish, and the more is known, the better management is expected.

Fish depends for their basic necessities on the water in which they live. The most characteristic feature of an aquarium system is, therefore, the quality of the water available in tanks/aquarium. This water must be obtained from some source, pre-treated to make it suitable for the fish, delivered to the fish in sufficient quantities and maintained in good condition. The water supplied to an aquarium is not pure, but it contains dissolved and particulate materials, some are necessary for up keep of the fish and rests are harmful. Contamination may occur not only at source or from the animals, but often takes place within the aquarium from the materials used for its construction. The number of fish that can be maintained within the aquarium is said to be according to the quality and quantity of the water supplied to an aquarium. However, it is rarely the quantity of water per unit which limits the carrying capacity. The capacity is usually set by the requirement of dissolved oxygen and the accumulation of toxic metabolic products in the aquarium.

One of the attractions of ornamental fish keeping is to multiply the fishes in captivity. Although techniques used for ornamental fish breeding are not much difficult, the breeding methods for specific ornamental fish species are closely guarded secrets. Farmers have operated almost entirely on their own, developing their own methods and rely on many years of experimentation. In India, the most important breeding centres for ornamental species are located in Kolkata, Mumbai, Chennai and Kochi. Ornamental fishes are broadly classified into two groups based on their breeding methods- Egg layer or oviparous and live bearer or viviparous species. Oviparous fishes lay floating, adhesive or non-adhesive eggs that may be scattered, laid in bubble nests or deposited on substrates or in shallow pits. The breeding and rearing of live bearers are easier than egg layers, which begin with handling the live bearers.

The indigenous ornamental fish which are very popular overseas, are being harvested from the wild and exported. This in the long run, may lead to depletion of stock due to over harvesting of our valued native fish species. Hence, breeding of native fish species is also equally important for a sustainable trade of ornamental fishery and to conserve the natural stock. Some fishes breed naturally with ease, whereas others are bred by artificial techniques like hand stripping and hypophysation. In nature, the fishes are stimulated by changes in environmental factors. These conditions can be simulated to some extent in the aquaria by providing specific biological requirements for spawning.

I. Breeding of Zebra danio (Brachydanio rerio)

Brachydanio rerio is commonly known as zebra danio. The zebra danio, as the name implies, is characterized by a number of bright blue or purple horizontal lines, which run from the head to the caudal fin. This pattern is repeated in the anal and caudal fins too. The flanks have prussian blue colouration and operculum has golden blotches. The dorsal fin of this species has an olive yellow base and there are blue gold markings on the anal fin.

As the ornamental fish industry expands throughout the world, genetic considerations have become more important in terms of production, sustainability and conservation. Genetic technologies are now being applied to increase food production in aquaculture through traditional and modern breeding programmes. Genetic markers can help to manage capture fisheries and distinguish farmed from wild stocks in mixed fisheries. Genetic technologies are also now finding application in post-harvest and trade to assist in product identification and traceability. Genetic improvement of fish has considerably increased the fish production from aquaculture. It includes selective breeding, hybridization, polyploidy, gene and nuclear engineering. For any genetic selection programme, induced breeding is the basic and initial step. Intensive selective breeding is practiced with various species of fish in perfecting appearance, shape and color so that new strains are produced.

Domestication

Most of the fish being widely grown in captivity are domesticated to some extent, but there are very few which have undergone genetic improvement. Just as terrestrial livestock and crops are bred to be not only productive, but productive in convenient proximity to humans, aquatic plants and animals are now undergoing these same pressures.

In comparison to agriculture crops, fruit plants and animals, aquaculture is much behind with regard to the domestication of the fish, especially ornamental fish. Never the less, a good number of ornamental fish have been domesticated which can be considered for selective breeding to improve their traits. The available technologies and tools could be used to remarkably speed up domestication and genetic improvement process.

Domestication implies much more than merely keeping wild animals in farms or homes. Domestication is a very long process, during which captive individuals become more adapted to captive environments. Domestication leads to permanent genetic modifications of a bred lin-eage, while taming or keeping wild fish in captive conditions is only conditioned behavioral modification of individuals. The entire life cycle of the domesticated fish species must be fully closed in captivity. Once full life cycle is completed in captivity, the process of domestication can proceed further.

The first truly domesticated fish species was certainly the goldfish, for which the domestication was initiated by the Chinese about 1500-2000 years ago.

Ornamental fishes are very prone to diseases due to their captive habitat. Fish health management is an important issue of concern at all the ornamental fish production facility. Proper water quality is required to be maintained in the aquarium for the good health of the fish. However, the chance of infection in these fishes is very high. Many limiting factors viz. water quality, over crowding, nutritionally imbalance food, rapid fluctuation in water temperature, lack of oxygen or poor husbandry practices influence the health status of the stock. The symptoms/signs indicate whether the fish is suffering from a particular disease or not. If the fish are observed to be swimming actively and there is no noticeable abnormality in the behaviour, it means there is nothing to worry about the health of the fish in the aquarium. On the other hand, diseased fish may look off colour, restless and/or behave erratically. In such a situation, the fish should be closely observed for visible infection and remedial measures should be taken immediately. Stock improvement in terms of disease prevention must be a top priority issue. In order to achieve healthy fish species, it is necessary to have a health management protocols in every farming practices.

Ornamental fish breeding and trade provide excellent opportunities for employment and income generation. One of the most critical determinants of the success of the trade is the problem of delivering a quality product to the market. The know-how of collection, critical handling, packaging methods are essential for serving the successful transport of live tropical fish to their final destination. However, a major impediment in expanding the trade of indigenous fishes is the poor roads/communication from most of the collection/landing centres to the town, non-availability of oxygen packaging at remote collection centres, difficulties in transportation of the collected fishes to the agent/stockist. Transportation of live fish and shellfish from areas of collection to destination or from areas of farming to the destination is an important activity of ornamental fish industry.

Proper collection, packing and transportation may help in increasing trade to a greater extent. Ornamental fishes destined for marketing, both domestic and export, have to use modern post-harvest technology or modifications of the current post-harvest technology to improve the post-harvest and post-shipment survival that is critical to the industry. It is in this context that the significance of packing and transport come into the picture. To overcome the problem of high mortality of fish species at different stages during transportation, it becomes essential to evaluate the most suitable and ideal condition for transportation. At present, the mortality rate during fish catching, collection, transportation is very high. The claim by the importers due to DOA (Death on Arrival) from India is on the higher side compared to the consignments from other developing countries. This is due to the lack of appropriate technology for fish packing & transportation/ shipment. Similarly, since the airfreight charges are very high, the exporters have no idea of the optimum number of a particular live fish to be packed in a container to reduce transportation cost. Such information is lacking for Indian fishes. The success of ornamental fish transportation depends on the following steps:

The purpose of managing a fishery is to maintain the resource so that it is renewable and therefore sustainable. Responsible aquaculture practices rely on sustainable production systems, to minimize impacts on the natural environment, and support resource conservation. In other words, the harvest of fish from the wild or their domestic culture, if performed with sound foundations of ecological and economic principles, can be sustainable and self-reliant commercial industry. In traditional subsistence fisheries, fishermen use primitive and inefficient gear to capture most ornamental fish. However, the supply of aquarium fish is not inexhaustible, and signs of over-fishing are becoming apparent in localized areas. With high demand and pricing of many beautiful species, ornamental fish are being harvested at greater volumes and higher rates, threatening the viability or sustainability of the fishery. Most endemic and sensitive species are restricted to very narrow specific habitats. Their survival, affected by physical over-exploitation for the aquarium trade, may be further hit by habitat alteration. No comprehensive studies have been carried out on the requirements of these endemic or sensitive exported species. In the absence of suitable impact studies, it is not possible to predict the impact of habitat alteration on these species. Exporters target more colorful varieties and since their ecological significance has not been studied, what long-term effect such selective exploitation will have on genetic diversity cannot yet be defined.

Apart from legislation that can be effectively implemented, eco-physiological and population studies of a quantitative nature are urgently needed to advise on the collection, maintenance and transport conditions that need to be followed by exporters to safeguard collected stocks from unnecessary mortality. Exporters are eager to learn and would be receptive to receiving appropriate, scientifically formulated, well-meaning practical advice. Studies should be targeted towards this end since it seems unlikely that the export trade can at present be voluntarily modulated on the basis of conservation requirements. Such a strategy could only become feasible after an adequately robust ecological database has been compiled, which would necessarily require time.

An effective management strategy needs to address not only aquarium-trade related matters but also policy and other matters in an integrated approach if we are to be hopeful of sustaining the ornamental fish industry in the long-term.

Ornamental fish culture has made giant strides in many countries in recent years. The industry is growing in leaps and bounds with involvement of even increasing number of aquarium hobbyists. A lucrative export market and high domestic demand have made ornamental fish industry a potential source for income generation. The range of species of ornamental fish available to the hobbyists is very large, with estimates of up to 1,500 species. As popularity of ornamental fish keeping has gained momentum, the need to transfer ornamental fishes from the resource abundant places to resource deficient places resulted in the marketing of ornamental fishes. In order to assess the marketing opportunities for ornamental fish, it can be classified as:

1. Choose the most appropriate option with a tick mark

i) Floating plants are required for breeding

a) Guppies

b) Angel fish

c) Swordtail

d) Gourami

ii) Breeding traps are generally used for

a) Egg-scatters

b) Egg-depositors

c) Livebearers

d) Nest-builders

“SOIL” the term is derived from Latin word “solum” which means, “floor”. Soil has been a defining component of humanity since the beginning of civilization. It holds the clues of past cultures, it supports the web of life connecting all ecosystems, provides materials to build houses, and provides the base for our food, feed, fiber and even some biofuels.

Soils are complex mixtures of minerals, water, air, organic matter, and countless organisms that are the decaying remains of once-living things. It forms at the surface of land and is the “skin of the earth.” Soil is capable of supporting plant life and is vital to life on earth. There are several general roles that soils play:

During the 19^th century various hypotheses were advanced about the origin of earth. These hypotheses can be grouped into two general classes:

1. Monistic hypotheses: The pioneers of this hypotheses believed that only one mass or body was responsible for the creation of the solar system. The representative of this theory is Nebular hypothesis. The advocates of this hypothesis were Kant and Laplace.

2. Dualistic hypotheses: The advocates of this hypothesis believed that two separate masses or bodies were responsible for the creation of the solar system. The representatives of this hypothesis are Planetesimal hypothesis and Tidal hypothesis. The pioneer of Planetesimal hypothesis was the great English scientist T. C. Chamberlain. The Tidal hypothesis was advocated by another English geographer named James Jeans.

Rock

A rock may be defined as “an aggregate of one or more minerals”. An aggregate of single mineral calcite gives rise to crystalline limestone. Granite is a combination of several minerals. Most rocks are hard and compact as granite and basalt, but some are loose and feebly aggregated as sandstone. Rocks possess certain characteristics such as structure, colour, specific gravity, cleavage and mineralogical make-up by which we can identify the rocks and also distinguish one from the other.

Mineral

A mineral is defined as “a natural substance, usually inorganic, having a definite chemical composition and commonly a definite molecular arrangement which is usually expressed in geometric form”.

Rocks and minerals formed under a very high temperature and pressure, when exposed to atmospheric conditions of low pressure and low temperature, they become unstable and weather. Soils are formed from rocks through the intermediate stage of formation of regolith (parent material) which is the resultant of weathering.

Soil formation takes place in two consecutive stages:

1. The weathering of rocks into regolith

2. The formation of true soil from regolith

The evolution of true soil from regolith takes place by the combined action of soil forming factors and processes. The first step is accomplished by weathering (disintegration and decomposition) and the second is associated with the action of soil forming factors which are known as pedogenic factors.

The pedogenic processes are dynamic and extremely complex involving several chemical and biological reactions, usually operating simultaneously in a given area. One process may counteract another, or two different processes may work in tandem to achieve the same result. Different processes or combination of processes operate under varying natural environments. The combined interaction of various soil forming factors under different environmental conditions set a furtherance to certain recognized soil forming processes. Pedogenic processes include:

There are over 100,000 different types of soil in the world, each with its own set of characteristics. If any soil is dug deep, one can see that it is made of layers, or horizons. The horizons together form a soil profile. Each profile tells a story about the life of a soil.

The development of soil profile is a constructive process where in disintegrated materials resulting from weathering of rocks and minerals get converted into a soil body. Soil Individual or Polypedon is a natural unit of soil that differs from its adjoining unit on the landscape in one or more properties. In modern soil taxonomy, polypedon is the unit of soil mapping. Apedon is the smallest volume recognizable in nature that can be called “a soil”.

Soil classification, or soil taxonomy as it is called, is grouping of soils in an orderly and logical manner based on soil properties (differentiating characters) for the purpose of studying and identifying them. The following are the purpose of soil classification:

To organize our knowledge of soils

To bring out and understand the relationships among the soils

To remember the properties of soils

To learn new relationships and principles in different soil groups

Physical properties of a soil greatly influence plant growth. The plant support, root penetration, drainage, aeration, retention of moisture and availability of plant nutrients are all linked with the physical condition ofthe soil. The physical properties of a soil which depend on the amount, size, shape, arrangement and mineral composition of its particles, also influence its chemical and biological behaviour.

Soil Structure Defined

Soil structure is defined as the arrangement of individual soil particles with respect to each other into a pattern. Structure describes the gross, over-all arrangement ofthe soil solids. In other words, soil structure is the ‘architecture’ of a soil.

Soils are composed of structural units, called “peds”. The peds consist of many individual particles, bound together by cementing agents like organic matter, clay and hydrous oxides of iron and aluminium. However, the strength of the bonds, the size and shape of the peds and the proportion of the soil particles involved in the peds differ considerably among soils.

Soil Consistence Defined

Soil consistence is the strength with which soil materials are held together or the resistance of soils to deformation and rupture. Soil consistence is measured for wet, moist and dry soil samples. For wet soils, it is expressed in terms of both stickiness and plasticity. Stickiness is the ability of soil materials to adhere to other objects. Plasticity is the ability of the soil materials to change shape continuously under a constant pressure and to retain the impressed shape when the pressure is removed. Soil consistence may be estimated in the field using simple tests or may be measured more accurately in the laboratory.

Soil Density

The density of a soil, as any other matter, is its mass per unit volume. However, in case of soil, because of its unique nature, the density can be expressed by two terms, viz., bulk density and particle density. Soil density is typically expressed in mega gram per cubic metre (Mg m^-3) which is numerically equal to g cm^-3.

Soil colour is the most obvious characteristic of soil. It has no direct effect on plant growth; however, it has indirect effect through temperature, moisture. Soil colour can indicate the climatic conditions under which it has developed and can be related to its parent material. It can also reflect upon its age, and the temperature and moisture characteristics of the climate. Thus, cooler regions tend to have grayish to black topsoils, due to the accumulation of humus. In moist warm regions, soils tend to be more yellowish-brown to red. Arid soils tend to be light in color (due to low organic content) and primarily express the color of their mineral content. Practically all colours occur in soils - white, red, brown, gray, yellow, black, etc. Predominantly soil colours are not pure, but mixtures. Frequently two or three colours occur, called as “mottling”.

15.1. Soil Temperature

Soil temperature affects plant growth directly; influences soil moisture, aeration, structure, microbial activity, decomposition of plant residues and availability of plant nutrients. Intermediate temperatures, near optimum for each crop, are the desirable temperatures for crop growth. Extreme temperatures are undesirable, lest crop growth would be retarded and weeds and germs may be favoured. Moderate daily variations are desirable as they lead to soil moisture distribution and aeration.

15.1.1. Factors Affecting Soil Temperature

The mean annual soil temperature is about 1°C higher than the mean annual air temperature. Soil temperature is influenced mainly by climatic conditions. The factors which affect the transfer of heat through atmosphere from the Sun also affect the soil temperature. The following are the factors that affect soil temperature:

Water is the elixir of life. It is required for the evapo-transpiration of growing plants. Water acts as a solvent and, together with dissolved nutrients, makes up soil solution from which plant roots derive nutrients. Soil water content controls soil air and soil temperature.

16.1. Forces of Water Retention

The forces responsible for water retention in soils are adhesion and cohesion. Adhesion refers to the attraction of solid surfaces for water. Cohesion refers to the attraction of water molecules for each other.

The force with which the soil particles retain water is defined in terms of pF scale (Schofield, 1935). pF is defined as “the logarithm to the base 10 of the numerical value of the negative pressure of soil moisture expressed in centimetres of water.”