PCA Plant Pathogens Final Exam
Questions Complete With Verified
Answers
\Q\.Which of the following is an example of mutualism: Fusarium causing vascular wilt, dodder
plant growing with tomatoes, Rhizobium generating nodules in the roots of legumes.
Why? - ANSWERS✔-Rhizobium generating nodules in the roots of legumes; allows rhizobium to
live and helps legumes by fixing nitrogen
\Q\.What are the common shapes of plant pathogenic bacteria? - ANSWERS✔-rods and spirilla
\Q\.In the Baltimore classification system, most plant viruses fall into which group? What is the
basis of this classification? - ANSWERS✔-+ssRNA group which is a single strand RNA that is
immediately ready for translation. The basis is the replication strategy of +ssRNA to -ssRNA to
mRNA then translated to proteins
\Q\.What does exclusion refer to in disease management? - ANSWERS✔-preventing the
introduction of pathogens in a new place
\Q\.What is the name of the pathogen that causes Cucumber bacterial wilt? - ANSWERS✔-
Erwinia tracheiphila
\Q\.What is the name of the pathogen that causes Soft rot of vegetables? - ANSWERS✔-
Pectobacterium carotovora
,\Q\.Explain the disease triangle. Illustrate how changes in one component can determine
whether a disease develops. - ANSWERS✔-For a disease to occur pathogens needs to be
abundant and virulent, environment in favorable conditions, and host is susceptible. A change in
one of these components can make it so conditions do not allow for infection. An exmaple is
not enough water for bacteria movement
\Q\.What is the main mode of bacterial reproduction in plants? - ANSWERS✔-binary fission
\Q\.True or false: All viruses contain both DNA and RNA - ANSWERS✔-false
\Q\.How do you distinguish between primary and secondary inoculum? - ANSWERS✔-primary is
initial causer of disease and secondary is the spread in the same season
\Q\.A hemibiotroph starts as a ______ but later switches to ______ - ANSWERS✔-biotroph;
necrotroph
\Q\.How do you distinguish between a biotic disease and an abiotic disease? Explain. -
ANSWERS✔-By observing the cause, progression, signs, and spread. Abiotic disease is over a
large area of land while biotic can affect a single plant. Signs like fungal mycelium and bacterial
streaming can give visual clues for biotic and testing like soil tests can help determine if abiotic
\Q\.What method is used to distinguish between Gram-positive and gram-negative bacteria?
What structural difference does this method detect? - ANSWERS✔-gram staining. Relies on the
gram positive bacteria having thick peptidoglycan layers in cell wall and gram negative bacteria
having thin peptidoglycan layers
\Q\.How is bacterium different from a virus? - ANSWERS✔-bacterium is a type of prokaryotic
heterotroph cell while virus is neither autotroph nor heterotroph and is made of genetic
material and capsid protein
, \Q\.How can one introduce genetic resistance in the plants for disease management? -
ANSWERS✔-breeding for desired resistance traits or genetic engineering
\Q\.Explain the role of T-DNA in crown gall disease. Which genes are involved in gall formation?
- ANSWERS✔-T-DNA is transferred from a Ti Plasmid into a plant cell. Genes coding for an
overproduction of cytokinin and auxin cause increase in cell division and size, creating tumors
\Q\.What are the four phases of a disease cycle in order? - ANSWERS✔-Infection, symptom,
survival, dissemination
\Q\.What symptoms is blight characterized by? - ANSWERS✔-chlorosis followed by rapid
necrosis
\Q\.Define chlorosis - ANSWERS✔-degradation of chlorophyll
\Q\.Define necrosis - ANSWERS✔-tissue or plant death
\Q\.Name any 4 genera of bacteria that cause plant disease - ANSWERS✔-Xanthomonas,
Pseudomonas, Erwinia, Agrobacterium
\Q\.What are two mechanistic ways that plants prevent high temperature stress? - ANSWERS✔-
vertical leaves and cuticular waxes
\Q\.Which of the following is NOT a function of the stylet (in nematodes): enzyme secretion,
withdrawal of host nutrients, reproduction, host tissue penetration - ANSWERS✔-reproduction
Questions Complete With Verified
Answers
\Q\.Which of the following is an example of mutualism: Fusarium causing vascular wilt, dodder
plant growing with tomatoes, Rhizobium generating nodules in the roots of legumes.
Why? - ANSWERS✔-Rhizobium generating nodules in the roots of legumes; allows rhizobium to
live and helps legumes by fixing nitrogen
\Q\.What are the common shapes of plant pathogenic bacteria? - ANSWERS✔-rods and spirilla
\Q\.In the Baltimore classification system, most plant viruses fall into which group? What is the
basis of this classification? - ANSWERS✔-+ssRNA group which is a single strand RNA that is
immediately ready for translation. The basis is the replication strategy of +ssRNA to -ssRNA to
mRNA then translated to proteins
\Q\.What does exclusion refer to in disease management? - ANSWERS✔-preventing the
introduction of pathogens in a new place
\Q\.What is the name of the pathogen that causes Cucumber bacterial wilt? - ANSWERS✔-
Erwinia tracheiphila
\Q\.What is the name of the pathogen that causes Soft rot of vegetables? - ANSWERS✔-
Pectobacterium carotovora
,\Q\.Explain the disease triangle. Illustrate how changes in one component can determine
whether a disease develops. - ANSWERS✔-For a disease to occur pathogens needs to be
abundant and virulent, environment in favorable conditions, and host is susceptible. A change in
one of these components can make it so conditions do not allow for infection. An exmaple is
not enough water for bacteria movement
\Q\.What is the main mode of bacterial reproduction in plants? - ANSWERS✔-binary fission
\Q\.True or false: All viruses contain both DNA and RNA - ANSWERS✔-false
\Q\.How do you distinguish between primary and secondary inoculum? - ANSWERS✔-primary is
initial causer of disease and secondary is the spread in the same season
\Q\.A hemibiotroph starts as a ______ but later switches to ______ - ANSWERS✔-biotroph;
necrotroph
\Q\.How do you distinguish between a biotic disease and an abiotic disease? Explain. -
ANSWERS✔-By observing the cause, progression, signs, and spread. Abiotic disease is over a
large area of land while biotic can affect a single plant. Signs like fungal mycelium and bacterial
streaming can give visual clues for biotic and testing like soil tests can help determine if abiotic
\Q\.What method is used to distinguish between Gram-positive and gram-negative bacteria?
What structural difference does this method detect? - ANSWERS✔-gram staining. Relies on the
gram positive bacteria having thick peptidoglycan layers in cell wall and gram negative bacteria
having thin peptidoglycan layers
\Q\.How is bacterium different from a virus? - ANSWERS✔-bacterium is a type of prokaryotic
heterotroph cell while virus is neither autotroph nor heterotroph and is made of genetic
material and capsid protein
, \Q\.How can one introduce genetic resistance in the plants for disease management? -
ANSWERS✔-breeding for desired resistance traits or genetic engineering
\Q\.Explain the role of T-DNA in crown gall disease. Which genes are involved in gall formation?
- ANSWERS✔-T-DNA is transferred from a Ti Plasmid into a plant cell. Genes coding for an
overproduction of cytokinin and auxin cause increase in cell division and size, creating tumors
\Q\.What are the four phases of a disease cycle in order? - ANSWERS✔-Infection, symptom,
survival, dissemination
\Q\.What symptoms is blight characterized by? - ANSWERS✔-chlorosis followed by rapid
necrosis
\Q\.Define chlorosis - ANSWERS✔-degradation of chlorophyll
\Q\.Define necrosis - ANSWERS✔-tissue or plant death
\Q\.Name any 4 genera of bacteria that cause plant disease - ANSWERS✔-Xanthomonas,
Pseudomonas, Erwinia, Agrobacterium
\Q\.What are two mechanistic ways that plants prevent high temperature stress? - ANSWERS✔-
vertical leaves and cuticular waxes
\Q\.Which of the following is NOT a function of the stylet (in nematodes): enzyme secretion,
withdrawal of host nutrients, reproduction, host tissue penetration - ANSWERS✔-reproduction
