Biological Sciences
Pathogenic Fungi
Pathogenic fungi are types of fungi that can cause diseases in humans, animals, and plants. They can infect their hosts through various means, such as through the air, soil, or direct contact. Pathogenic fungi can lead to a range of illnesses, from mild skin infections to serious systemic diseases, and they are a significant focus of research in medical and agricultural fields.
Written by Perlego with AI-assistance
10 Key excerpts on "Pathogenic Fungi"
eBook - ePubFungi Bio-prospects in Sustainable Agriculture, Environment and Nano-technology
Volume 1: Fungal Diversity of Sustainable Agriculture
- Vijay Kumar Sharma, Maulin P. Shah, Shobhika Parmar, Ajay Kumar, Vijay Kumar Sharma, Maulin P. Shah, Shobhika Parmar, Ajay Kumar, Maulin P. P Shah(Authors)
- 2020(Publication Date)
- Academic Press(Publisher)
Chapter 7PhytoPathogenic Fungi and their biocontrol applications
Indu Sharma* , Department of Biotechnology, Maharishi Markandeshwar Deemed to be University, Ambala, India *, Corresponding author. Email: [email protected]Abstract
Phytopathology is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Fungi are among the dominant causal agents of plant diseases. With respect to plant pathogens, fungi represent probably the most diverse group of ecologically and economically important threats. Most phytoPathogenic Fungi belong to the Ascomycetes and the Basidiomycetes. PhytoPathogenic Fungi use various strategies to colonize in plants and cause disease. PhytoPathogenic Fungi possess a wide range of enzymes destroying the carbohydrate polymers, which constitute the building materials of the cell walls. Some fungi kill their hosts and feed on dead material (necrotrophs), while others colonize the living tissue (biotrophs). For successful invasion of plant organs, Pathogenic Fungi developed strongly regulated and specialized infection structures. To further colonize hosts and establish disease, fungal pathogens organize a plethora of virulence factors and these interactions result in a broad spectrum of outcomes reaching from beneficial interactions to death of the host. Depending on the infection strategy, virulence factors perform different functions. While basically all pathogens interfere with primary plant defense, necrotrophs secrete toxins to kill plant tissue. In contrast, biotrophs utilize effector molecules to suppress plant cell death and manipulate plant metabolism in favor of the pathogen. Biological control of plant diseases with fungal pathogens has been considered a sustainable alternative method comparison to other chemical control. In plant pathology, the term biocontrol applies to the use of microbial antagonists to destroy diseases. Throughout their lifecycle, plants and pathogens interact with a wide variety of organisms. These interactions can expressively affect plant health in several ways. Different mode of actions of biocontrol-active microorganisms in controlling fungal plant diseases include soil amendments, hyperparasitism, entomogenous fungi, predation, antibiosis, cross protection, competition for site and nutrient and induced resistance. Successful application of biological control strategies requires more knowledge-intensive management. Commercial use and application of biological disease control have been slow mostly due to their variable performances under diverse environmental conditions in the field. To overcome this problem and in order to take the biocontrol technology to the field and expand the commercialization of biocontrol, it is important to develop new formulations of biocontrol microorganisms with higher degree of stability and survival. Future outlooks of biocontrol of plant diseases is bright and promising and with the growing demand for biocontrol products among the growers, mass production of biocontrol microorganisms and the use of biotechnology and nano-technology in improvement of biocontrol mechanisms, manage plant diseases, increase yield, protect the environment and biological resources and approach a sustainable agricultural.
eBook - PDFPlant Disease: An Advanced Treatise
How Pathogens Induce Disease
- James G. Horsfall(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
All rights of reproduction in any form reserved ISBN-0-12-356404-2 164 PAUL H. WILLIAMS I I . C O N C E P T U A L I Z A T I O N O F F U N G A L P A T H O G E N E S I S Disease in plants is the injurious alteration of one or more ordered processes of energy utilization caused by a continued irritation by a primary causal factor or factors (see Volume III, Chapter 3 ) . Although there are many causal factors, both animate and inanimate, that are capable of inducing disease in plants this chapter will be concerned with how fungi induce disease. Bateman (see Volume III, Chapter 3) has suggested that the relationships between symbionts, and in particular those involving pathogens and their suscepts, are sufficiently complex that none of the existing theories of parsitism are adequate to provide a sound conceptual basis for meaningful experimentation. Thus, he has proposed a multicomponent hypothesis, which relies on a complete understanding of the environments produced by and surrounding the symbionts in order to determine whether a relationship is mutualistic, commensalistic, neutral, or antagonistic. In the case of disease in plants, an unfavorable environment created by the pathogen confronts a fav-orable environment in the host, whereas, in resistance, an unfavorable environment produced by the host confronts the pathogen. Bateman has purposely defined the basis on which symbioses occur as broadly as possible, providing room for wide-ranging theoretical and experi-mental exploration. It is within the context of the multicomponent hypothesis, therefore, that I would like to consider fungal pathogenesis. The development of fungal diseases in plants is extremely complex and in many ways resembles the intricacies of a Shakespearean tragedy or a Thomas Hardy novel. In the play or novel, the protagonists are placed on stage or in a particular setting in some relationship with one another, and the story is set in motion with a communication of some sort.
eBook - PDFFungi
Biology and Applications
- Kevin Kavanagh(Author)
- 2005(Publication Date)
- Wiley(Publisher)
Fungal pathogens differ in their optimal environmental conditions required for inocu- lum production, dispersal and disease development. Often, disease development by fungal pathogens requires a minimum exposure time to particular tempera- ture and moisture combinations. For example, low relative humidity can reduce the development of powdery mildew disease of tomato caused by Oidium neolycopersici. 9.4 The disease cycle The disease cycle describes the events that occur from initiation of disease to the dispersal of the pathogen to a new host plant. This is distinct from the life cycle of the pathogen or plant that describes the stage or successive stages in the growth and development of an organism that occur between the appearance and reappearance of the same state (e.g. spore or seed) of the organism. Patho- genesis describes events that occur in the disease cycle from infection to final host reaction. Figure 9.2 depicts a generalized disease cycle. Inoculum is produced and dis- seminated, and after reaching its target host plant tissue (inoculation) it pene- trates the host. The type and mode of production of inoculum (e.g. sexual and asexual spores, resting spores, mycelium) and the method of dissemination (e.g. wind, water, insect) depends on the particular pathogen. For many important plant pathogens, a sexual stage has not been identified. Penetration is through wounds or natural plant pores (e.g. stomata), and some fungi produce special- THE DISEASE CYCLE 225 226 FUNGAL PATHOGENS OF PLANTS Production of inoculum Dissemination of inoculum Inoculation Infection Colonization Symptom development Figure 9.2 A generalized fungal disease cycle ized penetration structures called appressoria (singular = appressorium) (Figure 9.3). Having penetrated its host, the fungus then grows within plant tissue (infection). The incubation period defines the period between inoculation and infection.
eBook - PDF- Moselio Schaechter(Author)
- 2011(Publication Date)
- Academic Press(Publisher)
# Elsevier Inc. 2008, 2009, and 2011 105 caused by this disease. Other fungal diseases that have resulted in severe crop loss throughout recorded history in-clude the cereal rusts and smuts, ergot of rye and wheat, brown spot of rice, coffee rust, Sigatoka disease of banana, chestnut blight, and the downy and powdery mildews of grape. Those fungi found consistently in association with a particular plant disease are called pathogens. FUNGAL CHARACTERISTICS Fungi are eukaryotic, heterotrophic (lacking photosynthe-sis) organisms that, in most fungal groups, develop a microscopic, tubular thread called a hypha (pl. hyphae). A group of hyphae is known collectively as a mycelium (pl. mycelia), which makes up the vegetative (nonreproduc-tive) body or thallus of the fungus. In some fungi, the thallus is single-celled (as in the yeasts) or may be plasmodial (without a cell wall, as in slime molds). Although fungi lack a complex vascular system, they can form specialized structures for survival, dispersal, and spore production. Most fungi, except for a few groups, are not motile. Hyphae and Fungal Cells Fungal hyphae differ in diameter among species (3–4 to 30 m m or more micrometer wide) and may be septate (with crosswalls) or aseptate (coenocytic, without crosswalls). Septa usually contain small pores to ensure continuity with other cells. Fungal hyphae elongate by apical growth (from the tip). Hyphae grow over a surface stratum, may penetrate it, or may produce an aerial mycelium. In culture, fungi form colonies, which appear as collections of hyphae with or without spores that arise from a central cell or grouping of cells. Fungal cells from different hyphal strands may often anastomose, or fuse, to form a three-dimensional net-work. This process permits the development of specialized survival or dispersal structures such as rhizomorphs, sclero-tia, and fruiting structures, also known as sporocarps.
- Ahamad, Shahid(Authors)
- 2021(Publication Date)
- Daya Publishing House(Publisher)
Most plant diseases are caused by fungi belonging to about 50 genera. Potential pathogens have gained considerable attention and appearing to be promising as a biological control ( Table 22.1 ). Especially, using fungal antagonists against fungal plant viable supplement or alternative to chemical control (Papavizas, 1981, 1985). In the broad sense of biological control (Cook and Baker, 1983), crop resistance to disease is the ideal means of controlling diseases. However, many crops have little or no resistance to certain plant pathogens, so that biological control using microorganisms against plant pathogens is an attractive method for disease control. Considerable research has gone into the study of biological control of plant diseases over the past 60 years. In order to establish biocontrol efficacy there are many inherent obstacles to overcome. These include basic aspects of strain selection, efficient production of biomass, formulation, storage ability, and methods of application. Also, a better understanding of mechanisms of action, nutrition and ecology of biological control agents is needed. Further, the potential for genetic manipulation of fungi to create genetically superior strains or hybrids that can perform better than wild types empirically selected from the environment needs to be examined (Elzein and Kroschel, 2003). Mycorrhizas as Biocontrol Agents This ebook is exclusively for this university only. Cannot be resold/distributed. Over the last 30 years there has been an increasing interest in the potential role that both arbuscular mycorrhizal and ectomycorrhizal fungi can play in the control of plant diseases and various aspects of this concept have been reviewed (Borowicz, 2001; Graham, 2001; Sylvia and Chellemi, 2001; Barea et al., 2002). More than 80 disease biocontrol agents are on the market worldwide (Whipps, 2004), but none of these contain mycorrhizal fungi.
- Chandra, Ram(Authors)
- 2021(Publication Date)
- Daya Publishing House(Publisher)
Still, much remains to be learned about the microbial ecology of both plant pathogens and their microbial antagonists in different agricultural systems. Fundamental This ebook is exclusively for this university only. Cannot be resold/distributed. work remains to be done on characterizing the different mechanisms by which organic amendments reduce plant disease including those caused by fungal pathogens. More studies on the practical aspects of mass production and formulation need to be undertaken to make new biocontrol products stable, effective, safer and more cost-effective. Fungal pathogens are among the most important factors that cause serious damages and losses to plants. Harmful impacts of the chemical pesticides on the environment and non-target organisms have clearly been documented. The need for the development of non-chemical alternative strategies to protect plants against plant diseases including fungal pathogens is therefore clear. Biological control using fungal and bacterial antagonists to manage plant diseases seems to be a promising alternative strategy and have successfully been applied to control some diseases on different plants and crops. Biocontrol strategies may also be used to manage other plant diseases including foliar ones. Some of the important factors that affect the efficacy of microbial biocontrol agents in controlling plant diseases which should carefully be considered include method of application, formulation of biocontrol microorganisms and timing of application. Various composts and organic amendments as other means of biological control have also been tested on some plants and proven to be promising. There are many products composed of living organisms, primarily bacteria and fungi, being sold that claim they will increase plant health. However, for any material to be considered a biological fungicide the Environmental Protection Agencies and Organizations must register it (Bloom et al ., 2003).
eBook - PDF- Nwosu, Obasai(Authors)
- 2018(Publication Date)
- Agri Horti Press(Publisher)
It is the more important, therefore, to connote This ebook is exclusively for this university only. Cannot be resold/distributed. 6 Essentials of Plant Pathology whether the term is being used to apply to the disease or to the causal organism. In the case of diseases in which parasitic organisms are a part of the causal complex the diseased plant is commonly referred to as the host. While usage has made this the most widely used term, objection has been raised that it does not imply the actual relation which ordinarily exists between the plant and the pathogen. The term suspect is a newer word coined to apply to the plant which is subject to a given disease brought about by a given causal complex. The above terminology does not always strictly apply in the case of virus diseases. While the inanimate nature of viruses is not accepted in all quarters and practically nothing is known about their mode of increase or reproduction, they have above all in common with pathogenic microorganisms the property of being transmitted from plant to plant to become a part of the causal complex. While several schemes of nomenclature for plant viruses have been proposed, none has been fully accepted as yet. Therefore in current literature the student will find a great diversity among authors in method of reference to a given virus. They are not universal referred to as pathogens, and their disease-producing property is not commonly referred to as pathogenicity, largely because of the doubt that they are living entities. One system known as the Holmes system sets up a scheme of genera and species whereby each described virus is given a binomial. While this system has many admirable features, it is nonconformist in that it uses system set up for living organisms to classify what may well be nonliving organic compounds, which cannot be defined on the bases used in the binomial system for living organisms.
eBook - PDF- Dominique Blancard(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
3 Principal characteristics of pathogenic agents and methods of control 413 This page intentionally left blank 415 Fungi PhytoPathogenic Fungi are generally small and more complex organisms than bacteria. They are, sometimes visible to the naked eye but more often with the aid of a micro-scope. They are characterized by the forma-tion of free or interlaced filaments (hyphae), all of which constitute the ‘mycelium’. This can be coenocytic (without cell walls, as Pythium spp., Phytophthora infestans , and other Phytophthora spp., 1 Rhizopus stolonifer ), or with cell walls ( Alternaria tomatophila , Stemphylium spp., Botrytis cinerea , Pyrenochaeta lycopersici , Sclerotinia spp., Sclerotium rolfsii , Rhizoctonia solani ). It should be noted that some aquatic fungi are devoid of mycelium, as for example Olpidium brassicae , a vector of viruses and associated with the roots of soil-less tomato cultures. They often form amoeboid or plasmodial structures, sporangia, and uni- or bi-flagellate zoospores. On tomato, fungi also produce specialized structures, very resistant to adverse elements and perfectly adapted to their preservation. The most common are chlamydospores, thick-walled spores, for example Thielaviopsis basi-cola , Fusarium oxysporum f. sp. lycopersici , and Fusarium oxysporum f. sp radicis-lycopersici , Pythium spp. Pythium , like the Phytophthora , survives in the form of oospores which result from sexual reproduction. More visible, of variable size and equally effective for survival are sclerotia; these are dense mycelium masses, and are characteristic of certain fungi on and/ or in affected plant tissues: Sclerotinia sclerotio-rum , Sclerotinia minor , Sclerotium rolfsii , Botrytis cinerea , Rhizoctonia solani . During their distribution, fungi come into contact with the different tomato plant parts. Fairly quickly, spores germinate and produce an attachment structure called an ‘appresso-rium‘ which also serves to assist in the pene-tration of the host.
eBook - PDFMycorrhizas
A Molecular Analysis
- K R Krishna(Author)
- 2005(Publication Date)
- CRC Press(Publisher)
5 PLANT-FUNGAL SYMBIOSIS VERSUS PATHOGENESIS: MOLECULAR VIEWPOINTS Host reaction to fungal symbiont or pathogen may begin even before the establishment of any physical contact. Many steps leading to initial contact, formation of appresoria, production of inter- and intracellular structures, and molecular interactions that main-tain these two types of biotrophic partnerships could be similar. Infection by fungal pathogen results in activation of an array of defense mechanisms that restrict its multiplication. Hypersehsitive cell death, oxidative burst, accumulation of phytoalexins and induction of pathogenesis-related proteins are a few examples of host reaction to the pathogen. Many of these reactions occur even during the establishment of symbi-otic associations with mycorrhiza or rhizobia (Duffy and Cassais, 2000, 2003). Defense reactions are triggered in host tissue with the invasion of mycorrhizal fungus, but only in a transient and uncoordinated manner that fades away as symbiosis progresses (Gianinazzi-Pearson and Gianinazzi, 2003). Whereas, several other host reactions and end reactions can be diametrically opposite. At least broadly, if host Interaction with fungal pathogen leads to deleterious effects, a symbiotic relationship often im-parts physiological benefits. The physiological and molecular basis for such interac-tive effects on biotrophic partners are being studied; yet there exist numerous lacunae in our knowledge. A comparative study of fungal pathogenesis and symbiosis may provide us with some helpful leads in selectively enhancing symbiosis; at the same time, repressing pathogenesis. For example, a carefully tailored breeding program that enables the development of crop genotypes with resistance to fungal pathogenesis, simultaneously preserving/enhancing mycorrhizal component will have immense applied value in practical agriculture and forestry.
eBook - PDF- L.F. Diaz, M. de Bertoldi, W. Bidlingmaier(Authors)
- 2011(Publication Date)
- Elsevier Science(Publisher)
For plants, a variety of species are important pathogens; well known in this framework is Plasmodiophora brassicae. A selection of relevant plant Pathogenic Fungi is given in Table 9.6. 9.5. Parasites The presence of parasites or their infective stages in wastes or residues of plant, animal, or human origin depends on the nature of the wastes and the level of pretreatment. Parasites are of veterinary and medical importance if the raw materials used for composting are generated in wastewater treatment facilities or in slaughterhouses (e.g., contents of the digestive tract) and, in general, if the wastes are of fecal origin or contaminated with fecal matter. Some of the most important parasites of epidemiological relevance are listed in Table 9.7. From the protozoal ones, Cryptosporidium parvum seems to be the most relevant, while eggs of Ascaris species of humans and animals are the most important metazoic parasites. Parasites at large are not only important as pathogens, they may also be a risk factor as vectors in transmission of diseases from wastes to susceptible populations (e.g., by flies and cockroaches).
Index pages curate the most relevant extracts from our library of academic textbooks. They’ve been created using an in-house natural language model (NLM), each adding context and meaning to key research topics.
