eChapters

To isolate a streptomycin resistant mutant of E.coli by Indirect selection using Replica Plate Method.

Introduction

J. Lederberg & his wife E. M. Lederberg devised this technique in 1952.

U.V. light coming from the sun emits strong radiation to extent the antibacterial effect in the microbial population. However it has a very short penetration power, UV light is used as a mutagenic agent & was used by Beedle & Tatum to obtain biochemical mutation. The mutation rate is only once in 10^-9 cells per population. Then hence using mutagens like UV light by 10 to 1000 folds will increase this mutation rate.

In isolation of the mutant using UV light the dose of UV light is measured by its units/nm² organisms. The time selected for the mutation is calculated on the basis of 0.1 to 1% survival & a suitable biochemical character is used to evaluate the mutation.

A detailed treatment on the concepts of mutagenic effectiveness and efficiency was given by Konzak et al. (1965). They proposed the term “effectiveness” as a measure of gene mutations in relation to the dose and “efficiency” as an estimate of the mutation rate in relation to other biological effects induced, such as lethality, injury or sterility. To obtain high efficiency, the mutagenic effect must greatly surpass other effects in the cell, such as chromosomal aberrations, and toxic effects which generally lead to damage

Mutation
Definition: “Mutation is the change in our DNA base pair sequence due to various environmental factors such as UV light, or mistakes during DNA replication.”
What Are Mutations?
The DNA sequence is specific to each organism. It can sometimes undergo changes in its base-pairs sequence. It is termed as a mutation. A mutation may lead to changes in proteins translated by the DNA. Usually, the cells can recognize any damage caused by mutation and repair it before it becomes permanent.
A mutation is a sudden, heritable modification in an organism’s traits. The term “mutant” refers to a person who exhibits these heritable alterations. Mutations usually produce recessive genes.

Mutations are sudden heritable changes in characteristic of the organism, that is other than due to recombination (Swaminathan, 1983). Mutations occur naturally as spontaneous mutations and induced as spontaneous mutations and induced artificially by treating the biological materials with physical and chemical agents (mutagens). Experimental mutagenesis is effective method to enlarge genetically controlled variation, considerably within a short time.

Darwin’s theory of evolution explains that “variation is the mainspring of evolution”. The extent of genetic variability available in the breeding population and the selection techniques determine the efficiency of any breeding programme. In classical plant breeding programme, variation is generated by hybridization and selections are made from the resulting segregating generations. Induced mutagenesis can supplement hybridization or replace as a source of variability. Thus, mutation provides the raw material for crop evolution (Mahadeva and Randerson, 1982) and it provides the fundamental variability required for crop improvement by breeding (Konzak, 1984).

MUTATION BREEDING

Mutation refers to sudden heritable change in phenotype of an organism or permanent change in the number, kind and sequence of nucleotides in genetic material, while individuals showing these changes are known as mutants. Mutation was first discovered by Wright in 1791 in male lamb which had short legs. Hugo de vries coined the term mutation. In crop improvement the breeders are always look for wide range of variability and stabilization of desirable traits. Mutation breeding is very useful in inducing new variability, which is an essential requirement of any plant breeding programme. The modern day cultivars are the resultants of various breeding techniques like selection, hybridization, tissue culture and mutagenesis including some biotechnological tools. Novelty in commercial traits like colour, size, shape, length, post harvest life of flowers etc. are always valued and preferred by consumers. Mutation breeding by exposing planting material with irradiation has play vital role in inducing novelty in a number of flower crops.

MUTATION BREEDING

Mutation refers to sudden heritable change in phenotype of an organism or permanent change in the number, kind and sequence of nucleotides in genetic material, while individuals showing these changes are known as mutants. Mutation was first discovered by Wright in 1791 in male lamb which had short legs. Hugo de vries coined the term mutation. In crop improvement the breeders are always look for wide range of variability and stabilization of desirable traits. Mutation breeding is very useful in inducing new variability, which is an essential requirement of any plant breeding programme. The modern day cultivars are the resultants of various breeding techniques like selection, hybridization, tissue culture and mutagenesis including some biotechnological tools. Novelty in commercial traits like colour, size, shape, length, post harvest life of flowers etc. are always valued and preferred by consumers. Mutation breeding by exposing planting material with irradiation has play vital role in inducing novelty in a number of flower crops.

TYPES OF MUTATION

Based on occurrence

(1)Spontaneous mutation: Occur spontaneously in nature and not present in sufficiently high frequency and spectrum.

(2)Induced mutation: Artificially produced by the treatment of various mutagenic agents and present in sufficiently high frequency and spectrum

The discovery of mutagenic effects of X-rays on the fruit fly (Drosophila) by H. Muller in 1927 and by L. J. Stadler in barley and maize in 1928 paved the way for researchers to experiment with its effects on various organisms. In 1928, H. Stubbe showed the use of mutagenesis in producing mutants in crop plants like tomato, soybean and others. The first commercial mutant was produced in tobacco in 1934. Reports by B. Sigurbjornsson and A. Micke mentioned 77 cultivars that were developed through mutagenesis prior to 1995. In 1995, this number was 484. This number has since been significantly increased covering a large number of crops, namely, corn, wheat, pea, chrysanthemum, poinsettia, dahlia, citrus, apple, peach and the modified traits include plant maturity, winter hardiness, lodging resistance, protein and lysine content and numerous ornamental mutants. By the end of 20th century, the number of mutant varieties rose to 2252 covering a range of crops like cereals, oilseeds, pulses, vegetables, fruits, fibres, and ornamentals. Majority of these mutants were released as direct mutants and the rest as a result of cross breeding with the mutants. Most of the mutant varieties have come as a result of using physical mutagens (X-rays, gamma rays, thermal and fast neutrons) with gamma rays alone accounting for more than 60% of the mutant varieties. By 2017, nearly 3250 mutant varieties belonging to 175 plant species have been developed and released where China, Japan, India, Russia, the Netherlands, Germany and USA are the leading countries. India with 345 commercialized mutants stands third after China (810 mutants) and Japan (481 mutants). Thus mutation breeding is a significant contributor to the development and release of commercial cultivars in several crops and for several traits.

Mutations are sudden and heritable changes in the genetic material. They can result in deletion, inversion and translocation of certain portions in the chromosomes, which can result in the changed expression of a trait due to the interaction of alleles within or without the locus, sometimes the effects revert back or can be heritable.

Most of the fruit crops are highly heterozygous. However, heterozygosity is one of the advantages when it comes to mutation. In highly heterozygous crops wherein there is a need for improvement in a single trait, mutations have been of great use. One of main limitations is use of vegetative material, which due to the unlikelyhood of uniform penetration and distribution of mutagenic agent can result in chimera. Although hybridization and selection have made a fair dent in the improvement of fruit crops, mutation is one of the methods that can be relied upon to develop pre-breeding lines and to bring about change in the quantitavie traits. Another very important fact is that there are crops like grapes wherein a lot of spontaneous mutants have become established varieties viz., Sonaka and Saritha to quote a few. Some of the existing varieites wherein one or two traits need to be improved, mutation would greatly help in this in comparatively short time. In some of the crops like sapota, wherein the conventional breeding would take long time, mutation can be resorted to both for inducing variability in the germplasm as well as for trait improvement. It is also to be noted here that mutation breeding can be a good supplement for conventional breeding, more so with the emergence of tissue culture propagation, which often throws up spontaneous mutants. Mutation as a methodology can also be tried in some fruit crop spp where there is no disease resistance source within. It can also be adopted in cases where there is a need to break linkages.

Vegetables are cheaper source of carbohydrates, proteins, minerals, vitamins and dietary fibers, and hence, assume a place of very great importance in the diet of individuals. All kinds of vegetable are grown almost universally. India occupies the prime position in the production of vegetable crops and is the second largest producer of vegetables in the world. The area and production of vegetables in India have been increasing during the post-green revolution period, and the country is heading towards another revolution in the form of Golden Revolution. However, there is an utmost requirement for genetic improvement of vegetable crops in terms of productivity, qualitative characters and resistance to biotic and abiotic stresses. For any genetic improvement programme, the presence of genetic variation is pre-requisite and mutation is the ultimate source of this heritable variation.

Mutation technique that holds promise of generating a much wider desirable variability than classical breeding has been refined. Out of 2275 mutant varieties worldwide in all crops, as many as 66 mutants are in vegetables. In terms of percentage, China, India, USSR, The Netherlands, The United States of America and Japan account for 26.8, 11.5, 9.3, 7.8, 5.7 and 5.3%, respectively of mutagen varieties in all crops. Such varieties are 3% in case of vegetables. After mutation treatment by a mutagen to a specific plant, DNA alterations (deletion, duplication, inversion, translocation, or transposition of larger DNA fragments, or simple basic pair changes) occur and lead to the DNA sequence change. Hence, new characteristics of that plant are established. In fact, induced mutations supply us with many new plant lines, which may be used as primary materials for crop breeding. Hence, mutation breeding seems to be an effective and ultimate option to improve vegetable crops in the shortest possible time. A large number of new promising varieties in different crops, including vegetables, have successfully been developed worldwide using various mutagens (Chopra, 2005).

22.1 Introduction

Mutations are sudden heritable changes in the genotype of an organism. De Vries (1900) for the first time used the term mutation (mutare in Latin means ‘to change’) for the appearance of new types in evening primrose (Oenothera) plant. In 1901 he put forth the idea of producing mutations artificially for use in crop improvement. Alberto Pirovano (1922) was first to use X-rays and ultraviolet rays for inducing mutations in plants, but his work remained unknown. So, Muller (1927) became the first known to induce mutation in Drosophila fly using X-rays. Though Stadler (1928) had started working simultaneously on barley and maize and induced mutations, he was late in reporting mutation due to longer life cycle of these plants compared to Drosophila. Mutation may be gene mutation (the result of change in the nuclear gene or plasma gene) or chromosomal mutation (change in chromosome number, structure or chromosomal aberrations of various types).

Since genetic variability is essential for any crop improvement programme, the creation and management of genetic variability becomes central to crop breeding. Experimentally induced mutations provide an important source of variability. An advantage of such created variability is that the starting point can be an agronomically accepted cultivar rather than a genetic stock of no direct commercial value with many undesirable attributes. It should, however, be realized that none of the imposed treatments in a plant system has so far been able to direct a specific change. As a result, following mutagenic treatments, a mixed bag of induced variants is found and many of these may not be of any value. Also, many events take place concurrently in a treated cell to produce variation at several loci within a genome. Because of these reasons it will be unrealistic to expect miracles out of a mutation breeding programme. The desired results can be achieved only when the objectives are clearly defined and the experiments are specifically designed to achieve those objectives. When a mutant of the required type is obtained, we only reach the step of identification of a desired recombinant in a conventional breeding programme and all the succeeding steps of evaluation of the mutant are in no way different from those in the conventional breeding procedures.

Refers to entire operation of the induction and isolation of mutants.

Term mutation was introduced by Hugo de vries in 1900 in connection with sudden heritable changes observed by him in Oenothera.

Mutagenesis is the process whereby sudden heritable changes occur in the genetic information of an organism not caused by genetic segregation or genetic recombination, but induced by chemical, physical or biological agents.

Mutations were first identified by Hugo de Vries in the late nineteenth century, while experimenting on the ‘rediscovery’ of Mendel’s laws of inheritance. He coined the term ‘mutation’. Radiation-induced mutations as a tool for generating novel genetic variability in plants, advanced as a field after the discovery of the mutagenic action of X-rays demonstrated in maize, barley and wheat by Stadler. The discovery of X-rays by Rontgen in 1895 led to the application of X-rays for inducing mutations in fruit fly by Muller (1927). Mutation is of two types

A. Define/Explain the followings

1. Mutation: Sudden heritable change in the phenotype of an individual.

2. Macro-mutations: Mutations with distinct morphological changes in the phenotype are called macro-mutations. Such mutations are found in qualitative character and, therefore, are also called oligogenic mutations.

Mutation is defined as a sudden heritable change in gene or in chromosome structure. The process of hereditary change is termed mutation and the individuals affected by the change are called mutants. Besides recombinations, mutations are the cause of genetic variation from which every breeding activity proceeds. By means of mutations, the multiplicity of the types of a population is not only increased by one genotype, but also by large number of further new genotypes due to possibility of subsequent recombinations of mutant with the existing genotypes.

Mutation breeding is a method that uses physical radiation or chemical means to induce genetic variation in plants to develop new crop varieties. Mutation can be defined as a sudden heritable change in the character of an organism which is not due to either segregation or recombination. Mutation is the source of most genetic variation and the motor of evolution. It is a natural process, which occurs spontaneously and slowly over generations in plants, animals and all living beings. It involves alteration of their DNA, leading to the development of changes within the organism. Mutation may be sped up through the treatment of physical or chemical mutagens to achieve alteration in characteristics that are useful for the development of new variety of a plant species.
Spontaneous mutations
Spontaneous mutations are the net result of all that can go wrong with DNA during the life cycle of an organism (Glickman et al., 1986). Thus, the types and amounts of spontaneous mutations produced are the resultant of all the cellular processes that are mutagenic and those that are anti-mutagenic. Spontaneous mutations occur naturally without any apparent cause however, there are two possible sources of origin of these mutations.

Introduction

My journey into the heart of wildlife conservation began in the unassuming classrooms of KendriyaVidyalaya, where my curiosity for the natural world was nurtured by dedicated teachers and an enriching curriculum. My dreams took f light when I studied stories of Mahadevi Verma in my school days where she was taking care of wild animals in her home. Fuelled by my determination, I pursued my education in Veterinary College, Hebbal, Bangalore from 2006 to 2011. To increase my knowledge and help the wild animals in better way, I did master in Veterinary Microbiology from Veterinary College, Hebbal, Bangalore during 2012-2014, research was conducted in “Salmonellosis in Wild Animals” and PG diploma course in wild animal disease management from TANVAS, Chennai in 2016 research was on “Oral Microflora of Snakes”. Pursing higher studies gave direction to help wild animal, also gave me abilities to write research paper which will help the communities.

Mycobacteria are slender rods of varying lengths that sometimes show branching filamentous form resembling ‘fungal mycelium’. Hence, the name mycobacteria, meaning fungus like bacteria.
Although cytochemically gram positiive, the Mycobacteria do not take up the dyes of the gram stain because the cell walls are rich in lipids – Mycolic acid. Once a dye has been taken up by the cells they are not easily decolourised, even by acid-alcohol. Mycobacteria are therefore called as acid-fast bacilli. The genus includes animal and human pathogens as well as saprophytic members often referred to as atypical, anonymous, opportunistic, tuberculoid and MOTT (Mycobacteria other than typical tubercle) bacilli. Clasification of Mycobacteria (Tubercle Bacilli)
I. Slowly growing Mycobacteria
• Mycobacterium tuberculosis causes human tuberculosis in human and dogs.
• Mycobacterium bovis causes bovine tuberculosis in many animal species and also cause tuberculosis in human
• Mycobacterium africanum causes human tuberculosis.
• The human type (Mycobacterium tuberculosis) is primarily a pathogen for man. But can cause disease in cattle, pigs, dogs, monkeys, parrots and other species. The bovine type (Mycobacterium bovis) is a common cause of disease in domestic animal particularly cattle, pigs, cat, dogs and horse. The avian type (Mycobacterium avium) is primarily a pathogen for birds. But can cause disease in cattle, sheep, goat and pigs.

Etiology

The condition is characterized by formation of granuloma to pyogranulomatous dermatitis with paniculitis. The causative organism is normally present in the macrophage which may be Mycobacterium tuberculosis, M? bovis and M? microti.

Etiology

Genus Mycobacterium contains many pathogenic species that can cause disease in birds (M. avium, M. tuberculosis, M. genavenes, M. gordonae). Within M. avium, organisms are divided into four sub species. M. avium sp avium, M.avium sp silvaticum, M. avium sp homnissuis and M. avium sp paratuberculosis. Mycobacterium avium sp avium - has wide host spectrum; poultry, pigeons, raptors, ratites and wild birds. M. genavense- affects Psittacines and passarines. M. tuberculosis- psittacines and other cage birds, and wild birds in captivity. M.bovis- Psittacines and others.

Under natural conditions, M. avium sp avium does not cause severe disease in mammals except in rabbit and pig. Majority of mycobacteriosis in pigs is by M. avium sp avium. In cattle and other mammal infection by M. avium remain localized and is known to give positive reaction to mammalian tuberculin. The disease in caged and wild birds in captivity is common with M. tuberculosis, because of its close contact with humans. Tuberculosis is a serious problem in zoological gardens. M. avium is being isolated in increasing number of immunocompromized human patients.

In 1882, Robert Koch first isolated the organism, stained with alkaline methylene blue and vesuvin as counter stain and proved its etiologic relationship with Tuberculosis.  Ehrlich first developed acid fast stain in 1882 and used for better staining of the bacteria which was adopted by Robert Koch. Later this staining technique was modified by Ziehl-Neelsen, accordingly it is now a day known as Z-N staining. In 1890, Koch prepared a glycerine broth extract of the tubercle bacillus, known as ‘tuberculin’.

      He tried to prepare it as a curative agent; however, it was used later in diagnosis. In 1895, Johne and Frothingham described the first case of paratuberculosis in cattle, later known as ‘Johne’s disease’. Although, the causative agent was first isolated by Twort and Ingram in 1910.

            In India, bovine Tuberculosis was reported from several states since 1959 (Dhanda and Lal, 1959). Whereas bovine paratuberculosis was first reported by Nanda and Singh (1940) in Hissar, Haryana.

Introduction

Avian mycoplasmosis is caused by several pathogenic mycoplasma of which mycoplasmosis due to Mycoplasma gallisepticum (Mg), Mycoplasma synoviae (MS) and Mycoplasma meleagridis are important. The mycoplasma are group of bacteria that lack cell wall due to which the shape of bacteria is pleomorphic. Due to lack of cell wal, mycoplasma are resistant to those drug which act on cell wall and includes Penicillin and its derivatives. Mycoplasma primarily affects respiratory system and joints in birds and respiratory and urogenital system in humans. The avian mycoplasma are mainly transmitted by vertical route (egg transmission), but can also transmitted by horizontal route. Mycoplasma gallisepticum (Mg) causes chronic respiratory disease (CRD) in chicken, turkeys and game birds. Mycoplasma synoviae (Ms) causes infectious synovitis in chicken and turkeys whereas Mycoplasma meleagridis cause disease in turkey. The Mg and Ms belongs to class of Mollicutes (Molecutis: soft tissue), order Mycoplasmatales and family Mycoplasmataceae. The CRD caused by Mg affects respiratory system and air sac in presence of other respiratory pathogen/ stress or immunosuppression. Clinically, CRD affected birds show respiratory rales, gasping, nasal discharge, and rhinitis with mortality due to complication with other respiratory viral pathogens or E. coli infection. The Ms has affinity for tendon and ligaments of joint causing severe lameness due to tenosynovitis with mild lesions in respiratory system and air sac. The Ms affected birds show lameness, breast blister and increased culling of male breeder birds. The Mg and Ms causes significant losses in poultry industry due to decreased egg production, condemnation and downgrading of carcass and decreased hatchability. Mycoplasma meleagridis in turkey associated with air sacculitis and drop in egg production.

    Q.1.    How many species of Mycoplasma are responsible for causing mastitis?
    Ans.    At least seven species like Mycoplasma bovis, Mycoplasma Canadensis, Mycoplasma bovigenitalium, Mycoplasma alkalensis, Mycoplasma capricolium, Mycoplasma californicum, Mycoplasma disper and Ureaplasma sp. are responsible for causing mastitis

    Q.2.    Which herds are more prone to such type of mastitis?
    Ans.    The herds where milking hygiene is very poor and when the cows are imported from other farms or from public sale yards.

    Q.3.    Which organs act as common habitat of the Mycoplasma organisms?

The name Mycoplasma is originated from the Greek word mykes (fungus) and plasma (formed). It was first used by Albert Bernhard Frank, a German Biologist in 1889. He thought it was a fungus. An older name for Mycoplasma was Pleuropneumonia-Like Organisms (PPLO), referring to organisms similar to the causative agent of contagious bovine pleuropneumonia (CBPP). It was later found that the fungus-like growth pattern of M. mycoides is unique to that species. It was first isolated in 1898 by Edmond Nocard and E. Roux from bovine lungs. Whereas, Mycoplasma pneumoniae was considered as a virus previously. Eaton and his co-workers cultured the causative agent of human primary atypical pneumonia (PAP) or "walking pneumonia." It was known as "Eaton's agent." In the early 1960s, Leonard Hayflick, in Philadelphia, was first to isolate and cultivate the causative agent of primary atypical pneumonia and identified the agent as a Mycoplasma and named it Mycoplasma pneumoniae.

The mycoplasmas are microorganisms in the class Mollicutes. Of the nine genera in this class, five contain species of veterinary interest. The genus Mycoplasma, in which there are about 100 species, contains most of the animal pathogens. The first mycoplasma identified in 1890 was Mycoplasma mycoides subspecies mycoides, the cause of contagious bovine pleuropneumonia. Similar types of mycoplasmas which were subsequently identified were called pleuropneumonia- like organisms (PPLO).
Mycoplasmas, the smallest prokaryotic cells capable of self-replication, are pleomorphic organisms ranging from spherical (0.3 to 0.9 pm in diameter) to filamentous (up to 1.0 μm long). Because they cannot synthesize peptidoglycan or its precursors, they do not possess rigid cell walls but have flexible, triplelayged outer membranes.
Their flexibility allows them to pass through bacterial membrane filters of pore size 0.22 to 0.45 μm. Mycoplasmas are susceptible to desiccation, heat, detergents and disinfectants. However, they are resistant to antibiotics such as penicillin which interfere with the synthesis of bacterial cell walls. Based on 5s rRNA sequence analyses, the mycoplasmas have been shown to be linked phylogenetically to Gram-positive bacteria such as Clostridium species which have low guanine-cytosine content in their DNA. They require enriched media for growth, characteristically forming umbonate micro-colonies
when illuminated obliquely and microcolonies with a ‘fried egg’ dppearance in transmitted light. The dense central zone is due to extension of the microcolony into the agar. Mycoplasmas, which have relatively small genomes (approximately 800 genes) are fastidious in their growth requirements.
Most mycoplasmas are facultative anaerobes and some grow optimally in an atmosphere of 5 to 10% CO2. Nonpathogenic anaerobic mycoplasmas are found in the rumens of sheep and cattle. The genera Mycoplasma and Ureaplasma contain animal pathogens.

1. Introduction
Bioremediation is an environmentally friendly process that uses numerousdifferent microbes (e.g., fungi & bacteria), green plants, or combinations
of them to weaken and detoxify dangerous pollutants in a sequential orsuccessional manner. The pollutant composites are converted by biologicalorganisms through a response that takes place as part of their metabolicprocesses. They convert poisonous pollutants into carbon dioxide (CO2) andwater (H2O), microbial biomass, and other products that are less poisonous.The organic wastes are biologically degraded under controlled, harmless, andsafe condition into inoffensive products below the admissible limits establishedby supervisory authorities.

Mycorrhizal symbiosis is the most prevalent and important mutualistic association in plant kingdom. ‘Mycorrhiza’- the word means fungus - root, this association was reported by A.B.Frank in the year 1885. Nearly 95% of plant species form this mycorrhizal association. This serves as critical linkage between plant roots and soil and characterized by the movement of plant produced carbon to fungus and fungal acquired nutrients to plants. Through its hyphae this fungus absorbs the available P from soil and transports directly to root cortex. Mycorrhizal associations vary widely in structure and function. There are seven types of mycorrhizae (Table 1). These are endo (arbuscular), ecto, ectendo, arbutoid, monotropoid, ericoid, and orchidaceous mycorrhizae. Among them, endomycorrhizae and ectomycorrhizae are the most abundant and widespread

Mycorrhizae denote the symbiotic associations between plant roots and fungal mycelia. Literally it means fungal root. In 1840, Vittandini proposed that ‘tree rootlets are nourished by certain fungal mycelia which mantle them’. The first illustrations of mycorrhiza were published in the same year by Robert Hartig. However, in 1885 A.B. Frank coined the term “mykorrhizen” to the mutualistic symbiotic fungal association of roots (‘mykos’ fungus ‘rhizen’ roots). He characterized the sheath-forming fungi on tree as ‘ectotropisch’ (ectotrophic) and those without such compact sheath as ‘endotropisch’ (endotrophic). Fossil records reveal that mycorrhizae are as old as terrestrial plants.

The term ‘mycorrhizae’ was coined more than a century ago (Frank 1885) describing that the roots of most plants are colonized by fungi and transformed into fungus roots organ. Mycorrhizae result from a mutualistic symbiosis between plant roots and certain fungi. Roots of most flowering plants live in mutual symbiosis with mycorrhizae which bio-tropically colonise the root cortex and extra-metricial mycelia help the plant to obtain plant nutrients from soil (Barea, 1991).

These fungi are ubiquitous in soil and are found in the roots of many Angiosperms, Gymnosperms, Pteridophytes and Thallophytes (Mosse et al., 1981). The mycorrhizal fungi perform the function of root hairs. The fungus takes carbohydrates from the plant and in turn supplies the plants with nutrients, hormones and protects it from root pathogens. The dependency of fungal species on host plant ranges from obligate to facultative (Brundrett, 2002; Read and Perez-Moreno, 2003). The mycorrhizal plants have greater tolerance to toxic heavy metal, nigh soil temperature, soil salinity, unfavourable soil pH and to transplantation shocks.

They play an important role in increasing plant growth and nutrients uptake (Bagyaraj, 1992, VasanthaKrishna and Bagyaraj 1993). These fungi can be used to promote biotechnologically developed plant in soil (Varma and Schuepp 1994).

INTRODUCTION

The fine feeder roots of many vascular plants are invaded by specific nonpathogenic fungi forming a distinct morphological unit known as mycorrhiza (In Greek, Mykes mean mushroom or fungus, rhiza mean root). Physiologically mycorrhiza represents a case of symbiosis.

The term mycorrhizae were coined by a German botanist Albert Bernard Frank in 1885 which literally mean “fungus-roots”.  Mycorrhizal fungi form a symbiotic association with agricultural and horticultural crops in addition to certain tropical tree species.
Mycorrhizal fungi are broadly classified in to two groups:
1) Ectomycorrhizae  
2) Endomycorrhizae.

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 

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.

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.

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.