Plant Resistance And Defece Flashcards

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1
Q

Structural defences

A

Pre existing- hairs, stomata,surface coating, cell wall

Induced by pathogen- thick cell wall (bacteria and virus), outer parenchyma trap pathogens, callous deposition fungus repair and prevent penetration

Histological- cork, xylose, gum, abscission layers

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2
Q

Metabolic defences

A

Pre existing chemicals- tannins, dienes, phenolic compounds, inhibit plant cells
- missing factors are ressential nutrients, receptors for toxins and recognition factors

In response to pathogens
Phenolics- chlorogenic acid
Phytoalexins- only present in disease tissue, induced by elicitors, production suppressed by the pathogen eg. Isoflavanoids

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3
Q

Genetics of resistance

A

Host- resistance and susceptibility genes

Pathogen- virulence genes

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4
Q

Phenols to quinones

A

Polyphenoloxidase

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5
Q

Phenols to oxidised phenols and polymers

A

Peroxidase

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6
Q

PAL to phenol, phytoalexin, lignin

A

This

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7
Q

Other defences

A

Resistant substances, production of cyanide, detoxification of toxic products, induced resistance

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8
Q

Induced resistance

A

Can be local or systemic

Use pathogen proteins such as peroxidase or proteinase inhibitors

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9
Q

Hypersensitive reaction

A

Induces cellular and metabolic defences

Increased respiration, cell death, production of phytoalexins, accumulation of phenols, loss of membrane permeability

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10
Q

Horizontal resistance

A

Polygenic, doesn’t confer protection, difficult to quantify

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11
Q

Vertical resistance

A

Monogenic, strong hypersensitive response, prevents infection

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12
Q

Phytopethora facts

A

Zoosporic perfect fungus, wide host range, causes root, bud, tuber, seed rots and foliage blight

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13
Q

Phytopethora diseases

A

P. Cacterum- Lilly foot rot and apple trunk rot, wide host range, variable symptoms

P. Cinnamonia- avocado, cinnamon, chestnut rot, wide host range but sample symptoms

P.fagoniae- narrow host range

P.infestans- potato blight

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14
Q

P infestans

A

Larger genome than other species -240kb
Genome contains many transposons
Symplast genes- RXLR proteins, 60% more in infestans, cause hypersensitive response

Apoplast, many more hydrolases, like proteases

Ooomycete- water mould

Infects at all developmental stages- usual mid season

Spreads rapidly

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15
Q

Infestans disease cycle

A

Fungus can spread from tubers to potatoes via air borne spores.

Spores take 7-10 hours in moist and warm conditions to grow and spread

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16
Q

Infestans control

A

Practices- avoid night time irrigation, buy clean tubers, good storage

Chemicals- treat with preventative and eradicating fungicides

Crop monitoring and disease forecasts

Resistant varieties such as Snowden and Atlanta, not completely resistant though

17
Q

Potato blight symptoms

A

Starts with light to dark green circular or irregular leaf spot.

Turns into brown greasy wound on plant

Infected tubers appear distorted and purple in colour
Inside tubers have a dark red grainy appearance

Distinctive odor