eChapters

INTRODUCTION

Soil is known to harbour an array of micro-organisms. The soil micro-organisms play vital roles in the half-hidden portion of the plant i.e., the rhizosphere, where they are invariably present and are stimulated by organic substrates supplied by the plant. These are known to form the mutualistic, symbiosis with photosynthetic plants and play a key role in increasing availability of plant nutrients, the improvement of their uptake, the production of plant growth regulators, plant protection against root pathogens etc. in both natural and man-modified eco-systems.

11.1 Introduction

Our Country is a fast developing nation for the overall development and has proved that the country which was known for a begging bowl for food grains has turned up towards self-sufficiency and also has excess production to feed the present level of population. From about 50 MT of food grain production in 1950-51, harvest in 2010-11 reached over 241 MT, highest ever along with high production of fruits, vegetables, milk, egg and fish. This increased food production in the country has mainly been achieved through productivity gains, as the net sown area has remained static for the last four decades.

Abstract

In nature the roots of most of the plants are infected by fungi to form mycorrhizal associations, which play a central role in nutrient capture from the soil. These fungi are found in almost every terrestrial ecosystem; even in pioneer zones or very saline environments, and are reported to represent the second largest biomass component of many terrestrial ecosystems. Mycorrhizal associations are found in a broad range of habitats ranging from aquatic to deserts and alpine altitudes. In natural ecosystems mixed population of mycorrhizal fungi co-exist, with certain fungi becoming dominant in a particular patch and subsequently being replaced as environmental conditions change. Once this equilibrium is disturbed, the population dynamics is disrupted and a biomass may develop towards a few or even for one dominant fungus. Different species of mycorrhizae respond differently in response to the environmental conditions. In the present paper, all major types of mycorrhizal associations in different ecosystems are discussed.

Abstract

Sustainable landscape and forest management are of utmost concern in alleviating climate change. Fungal mutualism is one of the most significant positive biotic interactions responsible for forest structure and longevity. Coastal sand dunes imitate xeric habitats, while mangroves and river floodplains are often marshy. In spite of such extremities, mycorrhizal fungi are prominent component in coastal vegetation. Studies so far revealed that mycorrhizal association in herbaceous plant species is responsible for dune formation, stabilization and serve as potential inoculum in coastal habitats. Mycorrhizal association facilitates plant species to exploit larger volume of soil, supply nutrients (organic nitrogen, phosphorus and minerals), aggregates soil, provides tolerance to salinity stress, relieves from water stress and protects roots from pathogens. Human interference has severe impacts on plant-mycorrhizal mutualism in coastal habitats. Cultivation of exotic tree species and their uncontrolled exploitation further impoverish the habitats. Protection of native herbaceous flora, cultivation of native tree species and introduction of selected indigenous keystone species in disturbed habitats with mycorrhizal mutualism is an appropriate measure of rehabilitation.

Introduction

Soil has been advocated since the inception of nurseries as the storehouse of almost all the essential plant nutrients. Besides, it is treated as a living entity as it harbours diverse types of innumerable beneficial microorganisms, especially the beneficial genera of bacteria, fungi, actinomycetes, algae etc. In 1885, the German botanist, Albert Frank, introduced the Greek word ‘mycorrhiza’, which literally means ‘fungus root’. These fungi form a beneficial symbiotic association with the roots of higher plants and perform the functions of root hair. This symbiotic association has been reported to promote plant growth and health by playing the role of biofertiliser and bioprotectant, respectively.

Abstract
 
Much attention has been paid to mycorrhza as a tool for improving the growth and health of plants.  The use of mycorrhiza in agricultureal, horticultural and forestry has been described. The significance of AM fungi in sustainable agriculture has been a subject of growing interest for the past several decades. In sustainable agriculture it is imperative to maximize benefits with low input costs. The fact remains that stable and lower human population is an integral component of sustainable agriculture and more so in an Indian context. Therefore, it is imperative to collect further information on the different aspects of AM fungal symbiosis as discussed in this article so as to utilize this plant microbe symbiotic system for the increased production and productivity in a sustainable manner. This may become possible when the integrated approach is made to study AM fungi right from the isolation of AM fungal spores to the high quality inoculum production and its application in the field. It is also imperative to stimulate new mutualism between mycorrhizal scientists and ecologists. It this regard, recent advancement made in the molecular techniques should be encouraged in order to obtain more authentic results. Adequate field testing of mycorrhizal inoculation and commercial exploitation of the potential benefits of mycorrhiza still rests on the development of suitable technology for mycorrhizal inoculum preparation.

Sustainability refers to productive performance of a system over time. It implies use of natural resources to meet the present needs without jeopardizing the future potential. The Technical Advisory Committee of the Consultative Group of International Agricultural Research has defined sustainability as “Successful management of resources for agriculture to satisfy changing human needs while maintaining or enhancing the quality of the environment and conserving natural resources” (TAC, 1989). A sustainable system must be sustainable both ecologically and economically.

During the past several decades, production of horticultural crops has undergone a tremendous change in both developed and developing countries due to the development and use of fertilizers, pesticides, mechanization, soil fumigation, container production in soil-less media, breeding, micropropagation, pathogen elimination and a number of other innovations for attaining its future stability and sustainability. Recently, in modern horticulture, enhanced productivity depends heavily on inputs of fertilizers and pesticides to maintain an economic level of productivity. On the other hand, social and economic pressures are demanding that agricultural/horticultural practices, that have a damaging impact on the environment and pose risk to health of mankind, be curtailed. Thus throughout the world, agriculture including horticulture is at crossroads in terms of its future stability and sustainability. The solution for the above lies in developing new technology with reduced use of fertilizer and pesticides besides maintaining a sustainable level of productivity. The increased concern about the sustainability and undesirable side-effects of chemistry-based agriculture is prompting many researchers to more seriously evaluate alternative approaches. One such effort was put forth in the management of microbes that live in the rhizosphere soil around the roots of nearly all terrestrial plants. It has been believed that the main orchestrators of microbial activity in the rhizosphere are mycorrhizal fungi.

Introduction

There has been a steady increase in the poultry meat and egg production globally during the past few decades. Though the high biological value of eggs and poultry meat have resulted in an increasing demand for these two products, growing awareness for food quality and safety are becoming increasingly significant in determining the market value of such products. The importance of mycotoxins as one of the major detractor of poultry productivity and also of product quality, hence, becomes more relevant now than ever.

Introduction

The word mycotoxin is derived from myco, meaning mold and toxin, a poison. A great number of mold metabolites have been identified as mycotoxins. Thus mycotoxins are secondary fungal metabolites (i.e., metabolites not essential to the normal growth and reproduction of the fungus) which cause pathologic, physiologic, and/or biochemical lesions in other species (may include animals, plants, other microbes, etc.).

Mycotoxicosis - Poisoning of a biological system by a mycotoxin.

Mycotoxins  are  defined as toxic metabolites released by moulds under certain conditions conducive for their growth. Acute or chronic toxicoses can result from exposure to feed or bedding contaminated with toxins that may be produced during growth of various saprophytic or phytopathogenic fungi or molds on cereals, hay, straw, pastures, or any other fodder. A few principles characterize mycotoxic diseases:

Introduction

The word mycotoxin is derived from myco, meaning mold and toxin, a poison. A great number of mold metabolites have been identified as mycotoxins. Thus mycotoxins are secondary fungal metabolites (i.e., metabolites not essential to the normal growth and reproduction of the fungus) which cause pathologic, physiologic, and/or biochemical lesions in other species (may include animals, plants, other microbes, etc.).

Diseases caused by toxic metabolites of fungi are called mycotoxicosis. It affects man and animals including birds. Fungi which grow on feeds and grains in an unfavorable environment mostly cause mycotoxicosis in birds.

Introduction

Mycotoxins are substances produced by fungal infections which in some cases do protect plants or plant seeds against parasites (Schardl et al., 1996). However, upon ingestion, inhalation or dermal contact, these mold producing substances are poisonous to vertebrates. Even with more than 100,000 species of fungi known, only some of them are active mycotoxin producers. The fungi species which are known to produce the most hazardous mycotoxins in agriculture and in animal production are Fusarium, Aspergillus and Pencillium spp. Mycotoxins vary greatly regarding their toxicological effects as they do not belong to a single class of chemical compounds (Jewers, 1987). The environmental conditions in which they are preferably produced also differ. Fusarium toxins, such as trichothecenes, Zearalenone and fumonisins are commonly produced on the field, whereas aflatoxins and ochratoxins are produced by Aspergillus and Penicillium spp. mainly after harvest and during poor storage conditions.

Abstract

Mycotoxins are naturally occurring chemicals produced by fungi growing on grain, feed or food. The fungi that produce mycotoxins in grains commonly include Fusarium, Aspergillus and Penicillium species. The toxins can accumulate in maturing corns, cereals, soybeans, sorghum, peanuts and other food and feed crops in the field and in grain during transportation. The toxins may occur in storage under conditions favorable for the growth of the toxin producing fungi. Diseases in animals and human beings resulting from the consumption of mycotoxins are called Mycotoxicoses. These fungal metabolites are detrimental to the health of both animals and human. Toxicity ranges from acute death to chronic diseases, cancer and reproductive malfunction. Mycotoxin contamination of food and feed grains is a serious economic problem for grain producers and processors because grain contamination impacts market 

Mycotoxins are naturally occurring toxins produced by certain molds and can be found in food. The molds grow on a variety of different crops and foodstuffs including cereals, nuts, spices, dried fruits, apples and coffee beans, often under warm and humid conditions. Mycotoxins can cause a variety of adverse health effects and pose a serious health threat to both humans and livestock. The adverse health effects of mycotoxins range from acute poisoning to long-term effects such as immune deficiency and cancer. A scientific expert committee jointly convened by WHO and the Food and Agriculture Organization of the United Nations (FAO), called JECFA, is the international body responsible for evaluating the health risk from natural toxins including mycotoxins. International standards and codes of practice to limit exposure to mycotoxins from certain foods are established by the Codex Alimentarius Commission based on JECFA assessments.

Mycotoxins are toxic compounds that are naturally produced by certain types of molds (fungi). Molds that can produce mycotoxins grow on numerous foodstuffs such as cereals, dried fruits, nuts and spices. Mold growth can occur either before harvest or after harvest, during storage, on/in the food itself often under warm, damp and humid conditions. Most mycotoxins are chemically stable and survive food processing. Several hundred different mycotoxins have been identified, but the most commonly observed mycotoxins that present a concern to human health and livestock include aflatoxins, ochratoxin A, patulin, fumonisins, zearalenone and nivalenol/deoxynivalenol. Mycotoxins appear in the food chain as a result of mold infection of crops both before and after harvest. Exposure to mycotoxins can happen either directly by eating infected food or indirectly from animals that are fed contaminated feed, in particular from milk.

? Secondary metabolites of toxigenic fungi on animal food and food ingredients which causes adverse effects when consumed.

? 1942-44: Mycotoxicosis in man and animals was recognized in Russia. Fatal outbreaks of “toxic alimentary aleukia”. 

? 1955: “Hepatitis X” in dog and in cattle and swine in 1957.

? 1960: “Turkey- X disease” and 100,000 turkeys died in England due to Aspergillus flavus infested ground nut meal.

? 1962: Aflatoxin was first isolated.

? Favorable conditions for growth of fungi: Min. 15% moisture (10-13%), relative humidity: 90-95% (> 70%), ambient temp. of 24-25ºC (4-35ºC).

? Moulds infested feed along with nutritionally poor and inadequate diet makes animal more susceptible to mycotoxins induced harmful effects.

? More than 100 toxigenic fungi and mycotoxins have been identified during the last three decades.

Fungi cause diseases in plants and animals and in such diseases, the fungi actively grow and invade the body of their hosts. There is another means by which fungi can cause harm is growing on stored food material that we consume and produce toxic metabolites referred to as mycotoxins (means fungus poisons). Food is particularly susceptible to fungal infections at almost every stage of storage or production. Mycotoxin is toxic substance produced by a fungus. The term is restricted to toxins produced by fungi growing in human foods or animal feeds. The growth of the fungi in food grains leading to physical spoilage of grains and toxin production is a serious problem in developing countries. Their occurrence in food and feed has both economic and health implications, as the toxic effects in human beings, animals and other living systems were well established. The effects of poisoning by mycotoxin are referred to as mycotoxicoses.

The neoplastic disease primarily of broiler breeders and broilers causing serious economic losses in the commercial poultry industry. A case has been recorded in a budgerigar.

Etiology

ALV-J subgroup, identified in 1988. It became widespread in commercial meat type poultry in the 1990’s. Transmission of ALV-J is much higher than other subgroups thus making control much more difficult.

An inflammation of the muscular substance of the heart. The condition may be acute or chronic. Acute myocarditis may be sub-divided into three varieties:

1. Acute Parenchyma.
2. Acute Diffuse Interstitial.
3. Acute Circumscribed.

In the first of three classes, there is a glandular degeneration of the muscular fibres of the parenchyma of the heart and an increase in the number of their nuclei. Severe cases of this class often terminate in fatty degeneration.

In the second class, we have round-cell infiltration of connective tissue of the myocardium.

A family of about 150 genera and 3,800-5650 species, distributed mainly in sub-tropical and tropical regions of the world. Family is particularly abundant in Australia where some Eucalyptus trees are world’s tallest angiosperms. Myrtaceae is represented in India by about 15 genera and over 170 species. Beautiful pinkish flowers of Myrtus communis are considered highly sacred among Greeks, Egyptians, Jews and Persians, and used in religious rites and ceremonies. Some of the larger genera of Myrtaceae along with their number of reported species include Eugenia (1000), Eucalyptus (500), Syzygium (500), Myrcia (500), Psidium (140), Myrtus (100) and Melaleuca (100).
Eucalyptus spp. produce important components of medicinal and pharmaceutical applications. Economic parts are leaves and terminal buds-along with trunk. Lemon scented/ Tasmanian (E. globulus) is high in cineol content. Deodorant is manufactured besides utilization of oil for asthma, bronchitis, perfumery, etc. Phellandrene rich type, E. citridora (most widely grown in hill stations of southern parts of India). The source of citronellal and menthol from leaves and terminal buds is famous for perfumery industries.