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Plant Pathology > Oomycetes & Ascomycetes > Flashcards

Oomycetes & Ascomycetes Flashcards

1
Q

mycelium

A

The mass of hyphae that make up the vegetative body of a fungus

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2
Q

forma specialis

A

A fungal biotype that can only infect certain species of plants; analogous to pathovar

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3
Q

teleomorph, perfect stage

A

The sexual form in the life cycle of a fungus

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4
Q

anamorph, imperfect stage

A

The asexual form in the life cycle of a fungus, when asexual spores (such a conidia) or no spores are produced

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5
Q

pathogenicity VS virulence

A

P= The qualitative ability of an organism to cause disease

V=The quantitative ability of a strain of an organism to cause disease

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6
Q

germ tube

A

The first structure that emerges from a germinating fungal spore is called a germ tube.

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7
Q

appressorium

A

Swollen structure on the end of a fungal germ tube; a penetration peg emerges from it

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8
Q

vertical resistance VS horizontal resistance

A

Type of host resistance where essentially no disease develops on inoculated plants; race-specific (vertical resistance, specific resistance, complete resistance)

Type of host resistance where inoculated plants develop disease but less than fully susceptible plants; no races occur (horizontal resistance, general resistance, partial resistance)

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9
Q

Zoospore

A

A spore bearing flagella and capable of moving in water

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10
Q

Sporangium

A

A container or case of asexual spores. In some cases it functions as a single spore.

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11
Q

oospore

A

A thick-walled, sexual spore of an oomycete

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12
Q

Chlamydospore

A

A thick walled asexual spore formed by the modification of a cell of a fungus hypha.

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13
Q

Ascomycete

A

A group of fungi producing their sexual spores, ascospores, within asci.

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14
Q

Conidium

A

An asexual fungus spore formed from the end of a conidiophore.

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15
Q

Ascospore

A

A sexually produced spore borne in an ascus. (

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16
Q

ascocarp

A

A fruiting body of an ascomycete.

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17
Q

Acervulus (acervuli pl)

A

A subepidermal, saucer-shaped, asexual fruiting body producing conidia on short conidiophores.

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18
Q

Cleistothecium/chasmothecium

A

An entirely closed ascocarp (fruiting body of ascomyetes).

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19
Q

Sclerotium

A

A compact mass of hyphae with or without host tissue, usually with a darkened rind, and capable of surviving under unfavorable conditions.

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20
Q

Pycnidium

A

An asexual, spherical or flask-shaped fruiting body lined inside with conidiophores and producing conidia

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21
Q

Conidiophore

A

A specialize hypha on which one or more conidia are produced.

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22
Q

Perethecium

A

The flask-shaped ascocarp, having an opening or pore.

23
Q

Apothecium

A

An open cup- or saucer-shaped ascocarp of some Ascomycetes.

24
Q

race

A

A pathogen population that attacks a given set of plant varieties

25
Q

induced

A

Host defenses can be preformed or induced

26
Q

defense elicitors

A

Pathogen biochemicals that trigger host resistance are called ___.

27
Q

papilla

A

A plant cell wall deposition produced as a resistance response to fungal penetration is called papilla

28
Q

phytoalexin

A

Antimicrobial substance produced in plants in response to infection

29
Q

gene for gene theory

A

Theory that postulates that, for every host gene for resistance, there is a corresponding pathogen gene for avirulence; resulting from co-evolution of pathogen and host

30
Q

hypersensitive reaction

A

Rapid, localized cell death at the site of infection in resistant interactions between plants and pathogens

31
Q

toxins

A

Class of chemical weapons produced by necrotrophic pathogens that kill host tissue

32
Q

enzymes

A

Class of chemical weapons produced by necrotrophic pathogens that digest host tissue

33
Q

gums

A

Class of chemical weapons produced by pathogens that plug vascular tissue

34
Q

Systemic acquired resistance

A

Host plant resistance that is induced nonspecifically, is effective against a variety of pathogens, and is systemic. Can be induced by synthetic chemicals such as acibenzolar-S-methyl.

35
Q

gene silencing, RNAi/RNA interference/RNA silencing

A

Resistance to viruses whereby RNA viruses are destroyed or inactivated in the host cell… Eukaryotic mechanism by which specific RNA targets are destroyed or inactivated

36
Q

ceonocytic

A

Having multiple nuclei embedded in cytoplasm without cross walls; nonseptate (oomycetes)

37
Q

Downy mildew

A

A plant disease in which the fungus appears as a downy growth on the host surface; caused by a member of the oomycetes

38
Q

Flagellum

A

Hairlike, whiplike, or tinsel-like appendage of a motile cell, bacterium or zoospore that provides locomotion

39
Q

Fruiting body

A

Any of various complex, spore-bearing fungal structures fungus a eukaryotic organism that is usually filamentous (forming a mycelium) and heterotrophic, has cell walls composed of chitin, and reproduces by sexual and/or asexual spores

40
Q

sporangiophore

A

Sporangium-bearing stalk of a fungus

41
Q

sporangium

A

A container or case of asexual spores. In some cases it functions as a spore by germinating to form a germ tube

42
Q

zoospore

A

A spore bearing flagella and capable of moving in water (oomycetes)

43
Q

oomycete examples

A

Pythium and Phytophthora are members of this group of fungal-like organisms

44
Q

oospore

A

A thick walled, sexual spore produced by oomycetes; adapted for survival … can germinate to producte either a germ tube, sporangium, or zoospore

45
Q

Pythium symptoms and disease cycle

A

facultative parasites. Genus of fungal-like organism commonly causing seed rot and damping off … Source (=location) of primary inoculum of Pythium is from the soil, organic matter, including thatch… over winters as oospore or mycelium… disseminated by surface water, movement of soil/OM,

46
Q

pythium control

A

A systemic fungicide commonly used against Pythium seedling diseases (Metalaxyl/Mefanoxam) A contact fungicide commonly used against Pythium seedling disease (captan) Which event in the disease cycle for Pythium seed rot do contact seed treatment fungicides target? (infection) Which event in the disease cycle for Pythium seed rot does soil sterilization target? (survival) Which event(s) in the disease cycle for Pythium blight of turfgrass does water management target? (PPI, DPI, infection, colonization, PSI, DSI)
Which event in the disease cycle for Pythium blight of turfgrass does N management target? (infection, colonization, product of secondary inoculum) … Name a factor that can enhance Pythium diseases (soil wetness, high N, suboptimal or supraoptimal temperature)

47
Q

black shank of tobacco and disease cycle

A

P. nicotianae. facultative saprophyte. primary inoculum: soil, overwintering structure: chlamydospore. host range: tobacco. control: fungicides (mefanoxam/metalaxyl) , sanitation, resistance, rotation, soil drainage. symptom:stunting, wilting, foliar chlorosis, stem rot. dissemination: soil runoff, movement of sod, creeks, irrigation from ponds. infect: emergence sites for secondary roots, root apices. Sporangia of Phytophthora often can germinate directly (germ tube) or indirectly (zoospores). What environmental condition determines which will occur? (temperature)

48
Q

conidium

A

An asexual fungal spore formed from the end of a conidiophore

49
Q

ascus

A

saclike structure containing ascospores (typically eight) and usually borne in a fungal fruiting body

50
Q

downy mildew of grape and disease cycle

A

P. viticola. primary inoculum: dead leaves, live infected shoots. infects leaves, young shoots, berries by entering through stomata with haustorium. symptoms: leaf spot/blight, shoot blight, berry rot. secondary inoculum: sporangium, zoospore. control: contact fungicides (Bordeaux mix, mancozeb, which interupt infection) favorable conditions: cool & wet conditions; succulent growth, low light

51
Q

haustorium

A

A hyphal projection into live host cells which acts as an absorbing organ

52
Q

blue mold of tobacco and disease cycle

A

P. tabacina. overwinters: wild tobacco relatives in TX and Mexico. control: cultural- wider row spacing to increase air circulation, reducing leaf wetness (effecting infection, and production of secondary inoculum).

53
Q

powdery mildew of rose and disease cycle

A

Sphaerotheca pannosa f. sp. rosae. primary inoculum source: buds w/mycelium, cleistothecia on fallen leaves. product ascopores. dispersal of conidia and ascopores: wind. colonizes on plant surface. symptoms: leaf distortion, chlorosis, leaf necrosis, defoliation. sign: conidia and mycelium. secondary inoculum: conidia. control: contact fungicides like sulfur, systemic like propiconazole. oils, detergents, or baking soda also kills mycelium.
prefers soils high in N and infects juvenile tissue.

Plant Pathology (1 decks)

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