Rust Fungi

9 Key excerpts on "Rust Fungi"

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  The Model Legume Medicago truncatula

  • Frans J. de Bruijn(Author)
  • 2019(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  U. ciceris-arietini (chickpea rust), U. vignae (cowpea rust), U. trifolii-repentis, U. trifolii, U. minor, and U. anthyllidis (clover rusts), and U. lupinicolus and U. renovatus (lupin rusts). Species from other genera can also be of importance is some legumes, such as Phakopsora pachyrhizi and Ph. meibomiae (soya bean rusts) or Puccinia arachidis (groundnut rust) (Rubiales et al. 2011, 2015). Among these, in the present review, we will focus mainly on U. striatus which is an important disease of worldwide distribution, being particularly damaging in alfalfa grown for seed (Koepper 1942) and which can also damage M. truncatula extensively (Rubiales et al. 2011).

  Breeding for genetic resistance is the best measure for plant protection against rust, since chemical control can have negative environmental effects and/or high economic costs. The most commonly deployed strategy in rust resistance breeding is the single-gene resistance typically due to a posthaustorial defense mechanism, in which the plant cell collapses after the rust fungus starts to form a haustorium in the cells resulting in hypersensitivity (Niks and Rubiales 2002). Less exploited in breeding are the mechanisms of resistance acting before the formation of haustoria, but which can also contribute to increase the diversity of defenses to Rust Fungi. Indeed, rust infection can be hampered at very early stages of fungal development, from spore deposition to stomata recognition, resulting in a reduced penetration of the fungus into the tissue. This type of prehaustorial resistance is very common in nonhost interactions. However, it can also be a significant component in host interactions, being important in the typically polygenic, so called partial resistance (Parlevliet 1979), or in single gene resistances that proved to be durable. Examples are the Lr34 or Lr46

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  Soybean

  Biochemistry, Chemistry and Physiology

  • Tzi-Bun Ng(Author)
  • 2011(Publication Date)
  • IntechOpen

    (Publisher)

  This includes detailed knowledge of the life-style and the infection mechanism of a given pathogen as well as the defense reactions displayed by the host. The next paragraphs document the current status of knowledge in these areas. 2.1 Pathogen life-cycle and host range Rust Fungi belong to a group of fungi called basidiomycetes. They differ from other groups of fungi because the cells in most stages of the life-cycle contain two separate haploid nuclei, and the mycelium is referred to as dikaryotic. Rust Fungi of different species cause disease on several host plants but all of them have a so-called obliagtely biotrophic life-style in common; which means that these pathogens can grow and multiply solely on living host tissue. However, it has to be mentioned that after intensive efforts it is now possible to grow some Rust Fungi in axenic culture apart from the host plant. However, this has so far not been achieved successfully for the Asian soybean rust fungus P. pachyrhizi . Infection of soybean plants by P. pachyrhizi starts with the germination of a uredospore on the leaf surface (Fig. 2). Growth of the germ tube is terminated by the formation of a specialized, globose infection structure called an appressorium. The appressorium is separated from the germ tube by a septum. Since germination and appressorium formation also occur on water agar plates and artificial membranes it seems that both processes do not involve plant-derived signals (Koch and Hoppe, 1988). In these experiments a direct correlation was found between the frequency of appressorium formation and the pore size of the artificial membranes, which suggested the involvement of thigmo- rather than chemodifferentiation (Staples and Macko, 1994; Koch and Hoppe, 1988). Penetration of P. pachyrhizi into host epidermal cells is initiated within the appressorium by building of an internal structure called the appressorial cone which then elongates into the penetration peg (Bromfield, 1984).

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  Introduction to Fungi

  • John Webster, Roland Weber(Authors)
  • 2007(Publication Date)
  • Cambridge University Press

    (Publisher)

  Clamp connections are absent. 22.2 Uredinales: the Rust Fungi Rust Fungi (Uredinales) are a fascinating group of organisms. The life cycle of a typical rust species is among the most complex found anywhere in nature, consisting of five different spore stages on two plant hosts which are taxonomically entirely unrelated to each other. These patho-gens infect most groups of vascular plants, including Pteridophytes (ferns), Gymnosperms, and Angiosperms (both monocots and dicots). Numerous fundamental questions about Rust Fungi remain to be answered, e.g. how a bio-trophic organism manages to infect and para-sitize two unrelated hosts using different mechanisms on either; how the five spore stages with their numerous different dispersal mechanisms could have evolved; how easily one or more of them can become aborted in derived (reduced) life cycles; how Rust Fungi survive in situations where one of their two hosts is unavailable; and how quickly new rust species or races spread to new habitats and then come to an equilibrium with their host plants. A protocol to generate stable transformants of Rust Fungi would greatly facilitate experimental work on them, but unfortunately this is not yet available. The species concept in Rust Fungi is also challenging. Morphological species are readily recognized, but these can show considerable genetic adaptability by fragmenting into several forms which infect non-overlapping spectra of host species and thereby become reproductively isolated. Because of the identity of the host family as an additional taxonomic feature, spe-cies of Rust Fungi are relatively easily grouped into genera which are often monophyletic. At the higher taxonomic level, two large groups can be resolved weakly by phylogenetic analyses (Maier et al ., 2003; Wingfield et al ., 2004).

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  Plant Pathology

  • George Agrios(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  The cycle is thus completed. Some macrocyclic rusts, e.g., asparagus rust, complete their life cycles on a single host and are called autoecious. Others, e.g., stem rust of cereals, require two different or alternate hosts for completion of their full life cycle and are called heteroecious. The Rust Fungi spread from plant to plant mostly by wind-blown spores, although insects, rain, animals, etc. may play a role. Some of their spores are transported over long distances (several hundred miles) by strong winds and, upon landing (being scrubbed from the air by rain), can start new infections. Control of rust diseases in some crops, e.g., grains, is achieved by means of resistant varieties. In some vegetable, ornamental and fruit tree rusts, e.g., cedar-apple rust, the disease is controlled with chemical sprays. In others, e.g., white pine blister rust, control has been attempted through removal of the alternate host and avoidance of high rust-hazard zones. With the discovery of several new systemic fungicides effective against rusts, a new impetus has been given toward controlling rust diseases of annual plants as well as trees with these chemicals applied either as sprays, seed dressings, soil drenches, or by injection. CEREA L RUST S Various species or special forms of Puccinia attack all cultivated and wild grasses, including all small grains, corn, and sugarcane. They are among the most serious diseases of cultivated plants resulting in losses equiva-lent to about 10 percent of the world grain crop per year. Rusts may de-bilitate and kill young plants, but more often they reduce foliage, root growth, and yield by reducing the rate of photosynthesis, increasing the rate of respiration, decreasing translocation of photosynthates from infected tissue, and, instead, diverting materials into the infected tissue.

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  Fungi 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 7

  Phytopathogenic 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.

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  Fungi

  Biology and Applications

  • Kevin Kavanagh(Author)
  • 2017(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  14 Fungal Pathogens of Plants Fiona Doohan and Binbin Zhou 14.1 Introduction A wide range of fungi cause diseases of plants (see Chapter 1 for a description of fungal taxonomy, morphology, and reproduction). To be classified as a fungal plant pathogen or phytopathogen (phyto = plant), a fungus should, if possible, satisfy Koch’s postulates or rules. Koch determined that an organism was the cause of an infectious disease if it can: (1) be isolated from a diseased host, (2) be cultured in the laboratory, (3) cause the same disease upon re‐introduction into another host plant, and (4) be re‐isolated from that host. However, some fungal pathogens cannot be cultured, or in some cases it is not easy to carry out Koch’s tests. Since the early nineteenth century, thousands of fungi have been recognized as parasites of plants. Parasitism occurs where one species lives off another, as distinct from symbiosis where different species live in harmony with each other and the relationship is mutually beneficial, or saprophytism where organisms grow on dead organic matter. Plant‐pathogenic fungi are classified as: Biotrophs : only grow and multiply when in contact with their host plants (and therefore cannot be cultured on nutrient media); for example, the fungi that cause rusts, powdery mildews, and downy mildews. Non‐obligate pathogens : grow and multiply on dead organic matter (and can therefore be cultured on nutrient media) as well as on living host tissue. These can be further distinguished as facultative saprophytes or facultative pathogens. Facultative saprophytes complete most of their lifecycle as parasites, but under certain conditions they grow on dead organic matter

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  Biocontrol Of Plant Diseases

  • K. G. Mukerji, K.L. Garg(Authors)
  • 2020(Publication Date)
  • CRC Press

    (Publisher)

  71 The latter approach could be used when a natural control mechanism existed but is shown to be only partly effective. However, it requires a much greater understanding of the mechanisms of action of possible controls and of interactions with other environmental factors. An awareness that biological control works in nature should provide the greatest stimulus to utilize the capacity of the natural microflora to bring about disease control. There are four possible ways by which microorganisms can affect the propagules, infection, and fructification of pathogenic microorganisms, and reduce or control the development of a disease. They are (1) hyperparasitism, (2) antagonism by naturally occurring and foreign microorganisms, (3) immunization or cross protection, and (4) hypovirulence. Now we shall deal with them separately and in detail with examples of various rust and leaf spot diseases.

  A. Hyperparasitism

  Hyperparasitism is the attack of a secondary parasite on a primary parasite. The term hyperparasite refers to the parasitism of one microorganism by another; a mycoparasite is a fungus parasitic on another fungus. Unlike antibiotic producing microorganisms, hyperparasites do not initiate their parasitic activity at a distance, but require an intimate association of the host and parasite. Some hyperparasites obtain nutrients from the living host causing little or no apparent harm; this is “balance” or biotrophic parasitism.13 When the action of the parasite kills the host, the phenomenon is called necrotrophic hyperparasitism. It is the latter mode of action which is of most interest to those concerned with the biological control of plant pathogens. Hyperparasites of fungi were first observed in 1800s by mycologists interested in plant diseases. Most reports of hyperparasites suggest that they might be useful for biological control. The nature of hyperparasitism has been outlined by Barnett13 and the topic reviewed by several authors.

  24 ,27 ,40 ,43 ,46 ,87 ,100

  Kuhlman88 has discussed various attributes of hyperparasites providing biological control.

  1.  Rusts

  Basidiomycetous fungi, particularly the rusts, have been frequently noted as hosts of other parasites. Since the rusts produce external fructifications as a secondary inoculum helping the disease spread, they are liable to be controlled more effectively by hyperparasites than other disease such as leaf spots. Both primary and secondary inoculum can be parasitized, thereby affecting the disease at the time of infection, and later, the subsequent spread.

  a.  Fungi

  One of the earliest reported hyperparasites of rusts is Darluca. It occurs naturally on uredo- and teleutosori of numerous rust species. In early studies of asparagus rust, Smith145 observed the hyperparasite, Darluca filum, growing on uredinia of Puccinia asparagi. Later, the parasitism of Darluca on hemlock rust was studied by Adams2 who found that the mycelium of D. filum ramified throughout the pycnidial and aecial sori of Peridermium peckii

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  Essentials of Plant Pathology

  • Nwosu, Obasai(Authors)
  • 2018(Publication Date)
  • Agri Horti Press

    (Publisher)

  Cannot be resold/distributed. 22 Essentials of Plant Pathology vegetation of fungi arising under the epidermis of the plant. Fontana an Italian physicist, published a paper the following year in which he expressed the view that the grain rust was a distinct parasitic entity. This new theory received some support, no doubt, but the weight of opinion was against it. In this same decade Anderson, an Englishman, wrote concerning the degeneration of potato varieties which we now know to be due to infectious viruses. In 1778 he published evidence to show that the malady was tuber-borne and likened it to smallpox in its infectiousness. Zallinger in his book on plant diseases, “Demorbis plantarum” upheld the prevalent concept that fungi found in association with plant-disease lesions were abnormal structures of the diseased plants. MODERN PLANT PATHOLOGY It is apparent that at the beginning of the nineteenth century when Persoon and, a little later, Fries were actively naming and compiling fungi without reference to their relation to plant disease, those who were writing about these maladies were still not cognizant of the true relation to them of microorganisms. The first investigator to bring forth the facts which clearly demonstrated the pathogenic nature of any microorganism was Prevost, a Swiss professor of philosophy at the Academy at Montauban, France. He studied the wheat-bunt disease Jor about 10 years beginning about 1797. He published in 1807 his epochal “Memoir on the immediate Cause of Bunt or Smut of Wheat, and of Several Other Diseases of Plants, and on Preventives of Bunt”. After presenting an accurate description of the disease, he reported important results of experiments upon it. He studied and described the germination of the spores. He demonstrated, in confirmation of Tillet, that spores applied to the seed in some way resulted in infecting the plant.

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  Fungi From Different Substrates

  • J. K. Misra, Jalpa P. Tewari, Sunil Kumar Deshmukh, Csaba Vágvölgyi, J. K. Misra, Jalpa P. Tewari, Sunil Kumar Deshmukh, Csaba Vágvölgyi(Authors)
  • 2014(Publication Date)
  • CRC Press

    (Publisher)

  striiformis : (a) Uredinia on wheat leaf, (b) telia, (c) Teliospore, (d) basidia and basidiospore, (e) Berberis plant (alternate host), (f) pycnia on barberry leaf, (g) aecia on the lower part of the barberry leaf. 242 Fungi from Different Substrates seedlings of wheat, showed typical yellow striped lesions (uredinia) of the stripe rust of wheat (Jin et al., 2010). The role of the alternate host in the large wheat areas of the world in which stripe rust is important in producing new virulence combinations has to be determined. In the meantime, the asexual stage (urediniospore) plays the most important role in spreading the disease and in the life cycle of the stripe rust of wheat. Inoculum Production Studies of the cereal rusts require the increase and preservation of inoculum, which, in most cases, involve urediniospores. For many experiments, inoculum of a particular pathogen phenotype or a particular isolate is needed. In such situations, it is essential to be able to purify and maintain isolates over a period of years. In other cases, larger quantities of inoculum for field inoculation may require multiplication, collection and storage for various periods of time. This is particularly important for breeding programs in which one of the major goals is breeding for rust resistance (Fig. 11.11c). Color image of this figure appears in the color plate section at the end of the book. Figure 11.11. Bulk collection of urediniospores and field infection on the spreader row in a breeding stripe rust nursery. Rusts Fungi of Wheat 243 Spore Increase The usual procedure is to select a susceptible host. A local host line can be used if it is susceptible to the isolate to be increased. Sometimes it is possible to select a host that is susceptible to the isolate to be increased, but resistant to other isolates, eliminating some of the contamination problems.

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