Plant Pathology Exam 1 Study Set

Disease Triangle

Host, pathogen, and environment

Signs of disease

actual pathogen structures such as powdery mildew, ergots, etc.

Symptoms of Disease

wilting, canker, virus symptoms (mosaic and mottle leaf discolorations), fleck, galls, scab, and scalds

Koch’s Postulates

used to link a disease to a microbe/cause…the pathogen must be present in all cases of the disease. the pathogen must be isolated and grown in pure culture. the disease must be reproduced when the cultured pathogen is inoculated into a healthy host. the pathogen must be re-recovered from the infected host and must be the same as the pre-cultured disease.

Pathogen

bacteria, virus, microbe, etc. that causes disease

Saprophyte

something that lives off of decaying organic matter

Sclerotia

a dormant resting structure that allows for fungal diseases to survive during harsh environments

Gram-staining

A way to classify bacteria. Gram positive bacteria retain the blue colored crystal violet iodine complex. Gram-negative bacteria do not retain the blue crystal violet.

Vectors of disease

and organism that transmits an infectious pathogen (ex. leafhoppers and sharpshooters)

Bacterial motility

the ability for bacteria to move independently surviving off of its own metabolic energy and cellular structures

Symptoms of a plant infected with xylem-localized pathogen

prevents water flow so drought symptoms such as wilt, vascular discoloration, leaf scorch, and chlorosis

Insect vectors

feed on phloem sap of a plant transmitting phloem-localized pathogens.

Erwinia amylovora

Fire Blight

Pectobacterium carotovora

Bacterial Soft Rot

Pseudomonas syringae

Bacterial Speck

Ralstonia solanacearum

Bacterial Wilt

Xanthomonas axonopodis pv. citri

Citrus Canker

Agrobacteria tumefaciens

Crown Gall

Xylella fastidiosa

Pierce’s Disease on Grapes

Streptomyces scabies

Potato Scab

Clavibacter michiganensis

Tomato Bacterial Canker

Bacterial Canker of tomato

contains birds-eye lesions, rod shaped, gram positive

Bacterial Wilt

Can quickly kill plants by blocking xylem flow

Bacterial Speck

cells floruesce under UV light due to iron-gathering secretions

Citrus Canker

florida growers and homeowners fear discovery on their trees.

Pierce’s Disease of Grapes

hard to culture, lives within plant but not on their surfaces

Crown Gall

natural genetic engineer and alters the plant genome after infection

Fire Blight

Shepard’s crook-shaped shoot ends, necrotic leaves on branches of popular fruit trees

Soft Rot

stinky post harvest disease of potatoes and other root crops

Potato Scab

through a bacterium grows as a filamentous hyphae