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1 Zvyšování konkurenceschopnosti studentů oboru botanika a učitelství biologie CZ.1.07/2.2.00/ B. Mieslerová, A. Lebeda, (KB PřF UP v Olomouci)

2 PARASITIC SYMBIONTS Fungi come into association with their host, but in PARASITIC SYMBIOSIS only fungus benefits and the host is harmed FUNGAL PARASITES OF PLANTS, ALGAE AND OTHER FUNGI

3 FUNGAL PARASITES OF PLANTS Plants are attacked by insect, fungi, bacteria and viruses. However, about 60% of all plant diseases are caused by fungi. CLASSIFICATION OF PARASITIC FUNGI OBLIGATORY PARASITES strictly depend on parasitic life style (e.g. Erysiphales) FACULTATIVE PARASITES - organisms that can live either saprophitically or parasitically. Many of these are pathogens of crop plants, and must survive between growing seasons as members of the normal soil mycota (Fusarium oxysporum). Some of them are pertotrophs living on dead tissue in live organism. CLASSIFICATION OF PARASITIC FUNGI II. BIOTROPHIC PARASITES - parasite and host live together for longer periods of time. The parasite takes nutrients but does not kill it. Most biotrophic fungi are obligatory parasites. NECROTROPHIC PARASITES - necrotrophs kill host cells before they penetrate them by the secretion of extracellular cell wall degrading enzymes or toxins or both. Many necrotrophs show low specificity to host plants (Botrytis cinerea). The fungi are often only optionally parasitic, they can just as well proliferate in dead or withering plant material (facultative parasites).

4 GENERALIZED FUNGAL DISEASE CYCLE

FUNGAL INFECTION INOCULATION - Zoospores of Pythium, Phytophthora show tropism towards root exudates

development and growth on the plant surface.

structure specialized for firm attachment which is formed at the tip of hypha enables the infection peg

5 FUNGAL INFECTION INOCULATION - Zoospores of Pythium, Phytophthora show tropism towards root exudates (taxe of zoospores) INITIAL CONTACT attachment (extracellular matrix release), adhesion, appressorium development and growth on the plant surface. Initial events of colonization the fungus recognizes its host (elicitorsreceptor) APPRESSORIUM structure specialized for firm attachment which is formed at the tip of hypha enables the infection peg to exert mechanical pressure against the cell wall. The development of high internal pressure is essential for infection. Germinating powdery mildew conidia with appressorium

6 PENETRATION By stomata (rusts) By wounds (Venturia, Sclerotinia fructigena) By younger parts of tissue (root hairs) Direct penetration by enzymatic degradation (e.g. Powdery mildews). Many plant pathogenic fungi secrete a cutinase enzyme (cutin major structural protein of cuticle) and can degrade some polysaccharides of fungal walls (hemicelluloses, cellulose, lignin).

7 GERMINATION AND PENETRATION OF PATHOGENS Rust Downy mildew Powdery mildew Botrytis sp.

8 HOST PLANT COLONIZATION After penetration to host cell this cell may die immediatelly or can live (biotrophic pathogens) Formation of HAUSTORIA (involved in nutrient uptake) Normally the plasmalemma of the host cell is not broken, but forms an invagination so that the hypha is still topologically on the outside of it. Haustorium have an important role in the transfer of substances between host and fungus. Other possibility of nutrient supply - throught intercellular mycelium (Claviceps sp.) INTERCELLULAR OR EXTRAMATRICAL MYCELIUM - for spreading of pathogen DISSEMINATION OF PATHOGEN on plant surface

9 RESISTANCE MECHANISMS OF PLANTS PRE-FORMED HOST RESISTANCE STRATEGIES Structural barriers Thick wax or cuticle layer covering the epidermis Thick cell walls highly lignified walls Size, shape and location of stomata Hairs on leaf surface Metabolic barriers Low content of essential pathogen nutrients Pre- formed fungitoxic compounds (saponins of oats and tomato)

10 RESISTANCE MECHANISMS OF PLANTS II. INDUCED DEFENCE STRATEGIES Defence mechanisms that develop in response to infection 1. OXIDATIVE BURST, general reaction of plant cells to trauma involved a rapid production of hydrogen peroxide 2. HYPERSENSITIVE REACTION This is a rapid death of a few cells at the point of invasion, followed by cessation of fungal invasion visually visible as a spots. It is common response in race-specific resistance (biotrophic relationship cannot be established). HR involves a genetically programmed suicide of the cells surrounding the infecting fungus and both O 2 - and H 2 O 2 production (Oxidative burst) may participate in this response HR is particularly debilitating to biotroph, hemibiotroph pathogens, that require living plant tissue to survive)

12 Hypersensitive reponse of tomato leaf tissue as reaction on attack of powdery mildew

PAPILAE a localized thickening of the host wall where a hyphae penetrates a cell (presence of callose, lignin, suberin). Non-adapted pathogens may be inhibited.

13 PAPILAE a localized thickening of the host wall where a hyphae penetrates a cell (presence of callose, lignin, suberin). Non-adapted pathogens may be inhibited. Formation of papilae after penetration of germ tube of powdery mildew TYLOSES formed in xylem vessels as a response to abiotic stress protoplasts from the surrounding xylem parenchyma cells extend and protrude into the xylem throught pits blocking pathogen advancement through the vascular system.

14 5. MORPHOLOGICAL CELL WALL ALTERATIONS - e.g. lignification, suberinization formation of lignin in cell walls (lignin increase the resistance of cell walls to penetration and degeneration) 6. FORMATION CALLUS AND CORK CELLS AROUND INFECTION 7. PRODUCTION OF PHENOLICS AND PHYTOALEXINS. Phytoalexine low molecular weight compounds formed locally in plant cells in response to fungal invasion it inhibit fungal growth 8. PRODUCTION OF FUNGAL DEGRADING ENZYMES (chitinases, glucanases) AND DETOXIFICATION OF PATHOGEN TOXINS 9. LOCALIZED AND SYSTEMIC ACQUIRED RESISTANCE - resistance that develops in plants at a distance from the initial infection point. Weakly pathogenic fungus or a non-compatible pathogen can cause the plants to acquire resistance to subsequent challenge by a compatible pathogen oxidative burst, increasing activities of PR-proteins.

15 CONTROL OF FUNGAL DISEASES 1. CULTURAL PRACTISES quarantine, crop rotation (effective only if the resting stage persist for a single winter (problem in Synchytrium endobioticum), crop hygiene 2. FUNGICIDES - abiotic (sulphur, copper), contact, systemic 3. BREEDING RESISTANT LINES 4. BIOLOGICAL CONTROL use of living organisms or their products (e.g. Bacillus subtillis, Pseudomonas, Trichoderma harzianum, (antibiotics, mycoparasitism), Gliocladium, Ampelomyces quisqualis 5. INTEGRATED CONTROL combination of all methods

18 MAJOR GROUPS OF PLANT PATHOGENIC FUNGI 1. Biotrophic pathogens 2. Necrotrophic pathogens 1. Damping off, root rot pathogens 2. Pathogens on ripening fruits and fleshy tissues 3. The vascular wilts pathogens 4. Leaf and stem spots and anthracnose 5. Tree parasites

19 1. BIOTROPHIC PARASITES Parasite and host live together for longer periods of time Dependent on living tissues Most biotrophic fungi are obligatory parasites Do not produce large quantities of extracellular cell wall degrading enzymes or toxins. There is little or no immediate cell death. They have limited host range (host and organ specificity). They survive only limited saprophytic phases; especially the development of a fruiting body is dependent on the presence of a host The cultivation of single (vegetative) stages of these fungi in cell-free nutrient medium succeeded only in a few exceptions. Extracellular biotrophs Downy mildews (Peronosporales) Powdery milews (Erysiphales) Rusts (Uredinales) Smuts (Ustilaginales) Taphrinales Intracellular biotrophs Plasmodiophora brassicae, Spongospora subterranea (Plasmodiophoromycota) Olpidium sp. (Chytridiomycota)

20 DOWNY MILDEWS OOMYCOTA Biotrophic parasites with high host specificity Mostly with intercellular mycelium and haustoria in attacked cells. On the host surface forming sporangiophores with sporangia bearing zoospores Many parasitic oomycetes attacking land plants show adaptation of a zoosporangium to their life as terrestrial parasites. Sporangia break away and are dispersed whole, like large conidia (germinate directly by germ tube). PERONOSPORALES Plasmopara viticola, Bremia lactucae Pseudoperonospora cubensis Peronospora destructor Albugo candida Vřetenatka révová Plíseň salátová Plíseň okurková Plíseň cibulová Plíseň bělostná

21 Life cycle of Plasmopara viticola

22 Plasmopara viticola on Vitis vinifera Sporangiophores and sporangia

23 Bremia lactucae symptoms of disease Bremia lactucae sporangiophores

24 Pseudoperonospora cubensis sporangiophores and sporangia Pseudoperonospora cubensis, symptoms of disease on cucumber leaf

25 Peronospora destructor symptoms of disease on onion leaf Peronospora destructor sporangia a sporangiophores

26 Albugo candida Symptoms on Capsella bursapastoris Cross section of plant attacted by Albugo candida

27 POWDERY MILEWS ORDER ERYSIPHALES, ASCOMYCOTINA They are biotrophic parasites Mostly with white superficial mycelium, which penetrate to the host cells with haustoria. On the leaf surface forming conidiophores with conidia and at specific environmerntal conditions also teleomorph stage - cleistiothecia

28 Life cycle of Podosphaera leucotricha

29 POWDERY MILDEWS, ASCOMYCOTINA Germinating conidium Conidiophores and superficial mycelium Apendixes on cleistothecia Cleistothecium with one ascus Microsphaera Uncinula

30 Sphaerotheca mors-uvae Blumeria graminis Sphaerotheca fusca (Podosphaera xantii)

TAPHRINALES ASCOMYCOTINA Cause deformation and

the pathogen Taphrina betulina witches broom on

31 TAPHRINALES ASCOMYCOTINA Cause deformation and stunting (hypertrofy, hyperplasy) of leaves and branches (witches broom). Caused by growth hormones (auxins) liberated by the pathogen Taphrina betulina witches broom on birch Taphrina deformans on leaves of peach Taphrina pruni on plum fruit

32 UREDINALES (RUSTS) BASIDIOMYCOTINA Uredinales include about 4,000 species in 100 genera. They are characterized by the red-brownish colour (rusts) of their spores. Rusts develop haustoria and infect a range of angiosperms, gymnosperms, and pteridophytes. Puccinia graminis is the classic example of a fungus with an alteration of hosts. Its haploid (monocariontic) mycelium grows on Berberis (barberry), its dicariontic mycelium on different grasses. P. graminis is characterized by a complex alternation of generations. Up to five different types of spores can be generated during its course.

33 Life cycle of Puccinia graminis Types of spores: basidiospory spermacie aeciospory urediospory teliospory

34 UREDINALES Spermogonia with spermacia Uredia with uredinospores Aecia with aeciospores Telia with teliospores

35 Puccinia graminis teliospores Puccinia graminis aecia on Berberis sp.

36 Cronartium ribicola on Ribes sp. Cronartium ribicola aecia on Pinus strobus

37 Gymnosporangium sabinae, aecia on Pirus sp. Gymnosporangium sabinae, telia on Juniperus sp.

38 USTILAGINALES (SMUTS) More than 1000 species of Ustilaginales live parasitically on hosts of more than 75 angiosperm families. They produce dark, powder-like traces consisting of fruiting bodies strung together on leaves, shoots, flowers, and fruits. They develop usually no haustoria. Their extensive mycelium spreads through the intercellular spaces of the host plants.

39 Life cycle of Ustilago tritici promycel Basidie (sporidie) Chlamydospory (Teliospory)

40 USTILAGINALES Ustilago tritici chlamydospores (teliospores) Ustilago tritici, symptoms

41 Ustilago maydis, on Zea mays Ustilago segetum, on barley

42 BIOTROPHIC PARASITES INTRACELLULAR PLASMODIOPHORO MYCOTA Obligate parasites of high plants, algae and fungi Forming paraplasmodia in host cells Whole plasmodium transfered into sporangium Life cycle of Plasmodiophora brassicae

43 Roots of Brassica spp. attacked by Plasmodiophora brassicae Resting spores of Plasmodiophora brassicae

44 INTRACELLULAR BIOTROPHIC PARASITES CHYTRIDIOMYCOTA Olpidium brassicae, caused necrosis of hypocotyl at seedlings of Brassicaceae zoospores Synchytrium endobioticum, Germinated prosorus Sporangia in root cells

45 2. NECROTROPHIC PATHOGENS 2. A. DAMPING OFF, ROOT ROT PATHOGENS DAMPING OFF soft watery rot of parenchymatous tissue attached pectic substances in the middle lamella between cell. They include Pythium spp. which attack the emerging root tips Rhizoctonia solani, which characteristically attacks the young shoot base Sclerotium rolfsii which attack basal stem tissues Fusarium spp. which are seed-rot and seedling patogen. All these fungi grow rapidly in soil wet conditions and can ovelhelm the host in a short time. Their host range is characteristically wide, because they exploit tissues that do not exhibit the major defence mechanisms that vary between plant types.

46 Pythium sp., cause damping of young plants Sporangium of Pythium sp.

47 Sclerotium rolfsii on stem base of tomato Rhizoctonia solani -rot of cabbage

48 Fusarium root rot Fusarium spp. conidia

49 2. NECROTROPHIC PATHOGENS 2. B. PATHOGENS ON RIPENING FRUITS Ripening fruits and other fleshy plant tissues can be rotted rapidly by pathogens in appropriate conditions. All these pathogens caused rots by pectic enzymes which degrade the middle lamella, or cementing layer between plant cell walls. Botrytis cinerea causes grey mould of soft fruits such as strawberries, raspberries, grapes. Initiated growth on senescing flower remains and then invade the living tissue of the ripening fruit Penicillium italicum, P. digitatum which rot citrus fruits, Penicillium expansum rots apples (produce mycotoxin) Monilia fructigena rots apples, pears, peaches. Last three are wound pathogens enters through wounds

50 Botrytis cinerea, teleom. Botrytionia fuckeliana on grapes Botrytis cinerea on strawberry fruit Conidiophore with conidia Botrytis cinerea

51 Penicillium italicum and Penicillium digitatum on Orange

52 Penicillium expansum on apple fruit Conidiophores with conidia of Penicillium expansum

53 Coniophores with conidia of Monilia fructigena from an infected apple. Monilia fructigena, teleom. Monilinia on apple fruits

54 2. NECROTROPHIC PATHOGENS 2. C. THE VASCULAR WILT PATHOGENS AND OTHER ENDOPHYTES Vascular wilt pathogens cause some of the most devastating plant diseases Vascular pathogens can cause cell death by production of toxins (fusaric acid) and also cause cell death indirectly, by obstructing the flow of liquid in the xylem vessels and tracheids (Fusarium oxysporum, Ophiostoma ulmi). The vessels become blocked with hyphae and spores, fungal polysaccharides, or tyloses (produced by parenchymatous cells of plants) Systemic colonization of xylem leads to various symptoms such as yellowing and necrosis of the leaves, wilting and eventual death of the plant (often toxins have been implicated in vascular wilt) Caused by species of Fusarium oxysporum and Verticillium alboatrum (Hyphomycetes) and Ophiostoma (Ascomycetes) Enter via wounds or through the cortex of the young root region before the endodermis has deveoped

55 Conidia Fusarium wilt symptoms on tomato

56 Cut through a sunflower stem showing Verticillium wilt microsclerotia Verticillium wilt on tomatoes

57 Perithecium of Ophiostoma ulmi with mycelium Ophiostoma ulmi Dutch elm disease

stems Caused mainly by representatives of Deuteromycotina Leaf and stem spots (Septoria,

58 2. NECROTROPHIC PATHOGENS 2. D. LEAF AND STEM SPOTS AND ANTHRACNOSE Occurrence of localized lessions on host leaves and stems Caused mainly by representatives of Deuteromycotina Leaf and stem spots (Septoria, Cercospora, Ascochyta, Mycosphaerella), anthracnose (Colletotrichum) Cercospora beticola Skvrnatička řepná Mycosphaerella fragariae on strawberry leaves

59 Colletotrichum lindemuthianum on bean husk Septoria apii leaves on celery

60 2. NECROTROPHIC PATHOGENS 2.E. PARASITES OF TREE Tree are often killed by necrotrophic parasites Wound parasites Piptoporus betulinus, Polyporus squamosus only on weakened trees Some fungi can kill healthy undamaged tree - Armillaria mellea, Heterobasidion annosus. Penetrating to tree via roots. They may grow also as a saprophyte on the dead stumps of its victims. Armillaria mellea continued to live saprophytically on the wood after killing the tree

61 Heterobasidion annosum Aggressive parasite that infects cut stumps, spreads from root system to root system, and kills many different conifers

62 FUNGAL PARASITES OF ALGAE MARINE WATER More than 200 filamentous marine fungi have been described. Between a quarter or a third of them live parasitically on algae. Most of them belong to the Ascomycetes. Brown, red, and green algae as well as diatoms serve as their hosts. FRESHWATER Most parasites of freshwater algae belong to the chytrids. Chytrids are simple, non-mycelian fungi, reproduction by zoospores that find host by chemical cues.

63 FUNGAL PARASITES OF ALGAE - CHYTRIDIOMYCOTA Develop no hyphae, but a non-cellular and partially rather extensive system of rhizoids that seizes the host cells and can even enclose them. Nearly every known species of algae has its own specific parasite. The fungus infections should not be underestimated. Infections of nearly all algal cell-colonies have often been observed towards the end of a water bloom, i.e. the massive growth of an algal species. Chytrids infect both blue-green algae (Cyanophyceae) and green algae (Volvocales, as well as Chlorococcales). These groups of algae differ in the chemical composition of their cell walls so that the respective parasites have to have the most diverse enzyme systems at their disposal. The destruction of a cell occurs only after a cell-to-cell contact has been established, i.e. the fungus secretes no lytic substance into the adjacent medium that destroys all cells of a colony that are surrounded by a gelatinous coat.

64 Rhyzophydium sp. attacking Spirogyra sp. Rhyzophydium sp. attached Chlamydomonas Rhyzophydium sp. Sporangia on a moribund filament of Oedogonium

65 Chytridium versatile fungal parasite on Diatomas

66 Phlyctidium scenedesmi, on Scenedesmus Polyphagus euglenae on Euglena

67 FUNGAL PARASITES ON OTHER FUNGI Mycoparasitism about 3000 fungal species is parasitic on other fungi Some mycoparasites are BIOTROPHS. Most biotrophic mycoparasites are members of Zygomycotina (Piptocephalis). They absorbe nutrients from living host cells and have more narrow host range. NECROTROPHIC MYCOPARASITES (kill tissue of host) include some Deuteromycotina (Trichoderma, Gliocladium roseum), which have wide range of hosts and Oomycetes Pythium, Zygomycetes Spinellus. The attack may be physical (with the hyphae of one mycelium penetrating the hyphae of the other mycelium) or chemical (with the hyphae of one mycelium producing chemicals to dissolve the hyphae of the other mycelium) - or a combination of the two. When the host is itself a parasite, such fungi are termed HYPERPARASITES e.g. Ampelomyces quisqualis Macrofungi which parasitize other macrofungi (Boletus parasiticus on Scleroderma citrinum) is not easy recognise if they are biotrophs or necrotrophs Some of mycoparasitic fungi is used in biocontrol of other fungi Trichoderma against Sclerotinia, Botrytis, Fusarium.

68 FUNGAL PARASITES OF OTHER FUNGI CHYTRIDIOMYCOTA Some chytrids parasitize water moulds or other chytrids Rhizophidium chytriophagum sp.

69 FUNGAL PARASITES OF OTHER FUNGI - OOMYCOTA Pythium oligandrum (Po) parasitize on Botrytis cinerea (Bc). This species has been found also in spores of mycorrhizal fungus Glomus macrocarpum.

Piptocephalis unispora (Zoopagales, Zygomycotina) in a fungal

70 FUNGAL PARASITES OF OTHER FUNGI - ZYGOMYCOTINA Appressorium (ap) and a branched haustorium of the mycoparasite Piptocephalis unispora (Zoopagales, Zygomycotina) in a fungal host, Cokeromyces recurvatus Piptocephalis, parasite of other members of Mucorales

71 FUNGAL PARASITES OF OTHER FUNGI - ZYGOMYCOTINA Mycena sp., has been attacked by a parasitic fungus called Spinellus fusiger

parasitizes an underground fungus called Elaphomyces.

72 FUNGAL PARASITES OF OTHER FUNGI ASCOMYCOTINA Cordyceps capitata The fungus is widespread but not common and parasitizes an underground fungus called Elaphomyces. Cordyceps ophioglossoides This taxon also parasitizes sp. of Elaphomyces

73 FUNGAL PARASITES OF OTHER FUNGI ASCOMYCOTINA Hypomyces lactifluorum (Bysonectria viridis, Hypocreales), parasitize on Russulales (Russula, Lactarius) Perithecia

growth of Pythium, Rhizoctonia, also secrete chitinase and

74 FUNGAL PARASITES OF OTHER FUNGI - DEUTEROMYCOTINA Trichoderma produce antibiotics active against fungi or bacteria inhibit growth of Pythium, Rhizoctonia, also secrete chitinase and glucanase. Coiling of Trichoderma hyphae around the plant pathogen Rhizoctonia solani

75 FUNGAL PARASITES OF OTHER FUNGI - DEUTEROMYCOTINA Infection of conidia and germ tubes for Botrytis cinerea (BC) by Gliocladium roseum (GR)

It forms appressoria on the spores and hyphae of its hosts and penetrates

76 FUNGAL PARASITES OF OTHER FUNGI - DEUTEROMYCOTINA Ampelomyces attacks many powdery mildew fungi. It forms appressoria on the spores and hyphae of its hosts and penetrates them, extending from cell to cell Pycnidium of A. quisqualis which has formed in place of a conidium atop the conidiophore of Uncinula necator

77 FUNGAL PARASITES OF OTHER FUNGI BASIDIOMYCOTINA Asterophora parasitica. Obligate agaric parasites of agarics (Russulas in particular)) Xerocomus parasiticus. Found only as a parasite of the Scleroderma citrinum.

HYPHAL INTERFERENCE Several basidiomycotina antagonize other fungi, including other basidiomycotina, in contact. It occurs a few minutes after hyphal contact.

78 HYPHAL INTERFERENCE Several basidiomycotina antagonize other fungi, including other basidiomycotina, in contact. It occurs a few minutes after hyphal contact. The first visible sign is localized vacuolation and loss of turgor it leads to loss of membrane integrity. It does not seem to be parasitic mechanism because the aggressor hyphae does not enter the damage hyphae inactivate other hyphae (as a potential competitors for the same substrates) Hyphae of Heterobasidion annosum (previously termed Fomes annosus) have been antagonised where they were contacted by single hyphae of Phlebiopsis gigantea (previously termed Peniophora gigantea)

TIME-LINE OF INFECTION

TIME-LINE OF INFECTION Review of Lecture 8: Getting inside the host is a critical step in disease development Fungal pathogens use contact and chemical tropisms to guide their way to a site where infection is possible Pathogens