Bacterial diseases Flashcards
What are prokaryotes?
Usually single cellular organisms with no nucleus.
What is a gram test?
It is a test that helps determine if a bacteria is gram-positive or gram-negative.
What is the difference between a gram positive vs. a gram negative bacteria?
Gram-positive bacteria have a thicker layer of peptidoglycan on the cell wall whereas gram-negative bacteria have a thinner layer of peptidoglycan but instead they have an outer membrane.
Why is it important to know if a bacteria is gram-positive or gram-negative?
The different bacteria react differently to different pesticides.
How can you differentiate between gram positive and gram negative bacteria through a KOH test?
Gram -ve will be viscous slime and gram +ve will be no slime.
How can you differentiate between gram positive and gram negative bacteria through a gram staining test?
Gram +ve bacteria will stain purple whereas gram -ve bacteria will stain either pink or red.
What is one requirement for the bacteria to infect the plant?
Usually requires a critical mass of bacteria to colonize the host before infection.
What are 5 ways bacteria can spread?
- Wind
- Rain
- Aerosols
- Insects, Birds
- Humans
What are six symptoms caused by bacterial infections?
- Spots
- Rots
- Blights
- Galls
- Corks
- Wilts
What are four signs produced by bacteria?
- Bacterial exudate
- Slimy when fresh
- Bacterial ooze
- Streaming of Ooze
What are four symptoms of gram negative bacteria?
- Spots and blights.
- Rots
- Galls
- Vascular Wilts
What is one symptom of gram positive bacteria?
Common Scab
What were the two bacteria we swabbed in lab?
Xanthomonas translucens and Clavibacter
What kind of a bacteria is Xanthomonas translucens?
It is a gram-negative, non-spore-forming bacterium.
What bacteria causes bacterial leaf streak?
Xanthomonas translucens.
What are the four host plants for bacterial leaf streak?
- Wheat
- Barley
- Rye
- Triticale
How much yield can bacterial leaf streak reduce?
~40%
What are some signs and symptoms of bacterial leaf streak?
Water soaked streaks that develop into legions over time and yellow bacterial ooze on the surface of the leaves.
How can bacterial leaf streak spread?
Rain, winds, and aphids.
What does bacterial leaf streak eventually lead to?
It eventually leads to the flag leaves dying off and that leads to the plant unable to produce chlorophyll.
What is black chaff?
Black chaff is a symptom of bacterial leaf streak. This occurs when the bacteria has traveled to the plant’s head and results in legions on the head.
How does bacterial leaf streak survive?
Perennial weeds, and seeds of infected plants.
What are the favorable conditions for the growth of bacterial leaf streaks?
-Humidity
-15 - 30 degrees C
-Wounds for the bacterial to enter through.
What are four ways to control bacterial leaf streak?
- Use of certified seeds
- Treat seeds at 45 degrees for 20 mins.
- Resistant cultivars.
- Eliminating weed hosts and rotating to non-hosts.
What bacteria causes Goss’s bacterial wilt and leaf blight in corn?
Cavibacter michiganensis
What kind of a bacteria is Cavibacter michiganensis?
It is a gram-positive bacteria.
Where does cavibacter michiganesis overwinter?
In corn plant residue or other prairie grasses.
How does Goss’s bacterial wilt spread?
It can spread through seeds and wounds.
What are the favorable conditions for the growth of Goss’s bacterial wilt?
Wet weather and high humidity.
What are the two phases of Goss’s bacterial wilt?
- Systemic wilt
- Foliar blight (Blight on the foliage)
What are two symptoms exhibited during the systematic wilt phase of Goss’s bacterial wilt?
- In the cross-section of the stalk, vascular bundles have an orange color which turns brown after disease progression.
- Wilting
What are 1 sign and 2 symptoms exhibited during the foliar blight phase of Goss’s bacterial wilt?
- Sign: Bacterial ooze or exudate. The exudate usually appears shiny and white.
- Symptom: Black freckles.
- Symptom: Water soaked legions first which lead to streaks of tan legions at the edges of leaf blades.
What are the 4 ways to control Goss’s wilt?
- Reduce corn residue.
- Genetic resistance.
- Control weeds that are hosts for this disease.
- Prevention/Avoidance: Harvest and till affected fields last and make sure to clean equipment to prevent spread.
