Module 8 - Genetic Resistance to Disease

Question 1

what is resistance

Answer 1

the ability of an organism to either completely or partially exclude or overcome the effects of a pathogen or other damaging factors

Question 2

types of resistance in the host

Answer 2

• tolerance
  -escape
• non-host resistance
• systematic acquired resistance
  resistance due to individual genes with either large or small effect

Question 3

mechanisms of variability

Answer 3

mutation and recombination

Question 4

mutation

Answer 4

an abrupt change in the DNA of an organism (hereditary)

Question 5

recombination

Answer 5

fusion of haploid nuclei followed by meiosis resulting in crossing over

Question 6

why are we losing genetic variation in crops

Answer 6

we are breeding for uniformity, producing a genetic bottleneck

Question 7

3 strategies for conservation of diversity of plant genetic resources

Answer 7

1. In situlon farm
2. traditional gene banks
3. Svalbard global seed vault

Question 8

What is the Ressources Phytogenetiques du Canada

Answer 8

Seed bank in saskatoon that is trying to acquire, preserve, and evaluate the genetic diversity of crops and their wild relatives
Basically storing viable, diverse germplasm

Question 9

conditions for working collection seed storage

Answer 9

4 C, 10-20%RH in paper envelopes

Question 10

conditions for long-term seed storage

Answer 10

-18C, no humidity control, in sealed envelopes

Question 11

pathogenic

Answer 11

the ability of a genus or species of a pathogen to cause disease

Question 12

virulence

Answer 12

the ability of an individual entity to cause disease under defined conditions

Question 13

race

Answer 13

a group of pathogens within a specific species that can infect a specific set of plant varieties

Question 14

pathogenicity genes

Answer 14

those that are essential for causing disease. genes may include those for recognition of the host by the pathogen

Question 15

what does disease development require

Answer 15

the presence in the pathogen 1 or more genes for pathogenicity and lacks the gene for avirulence against the particular host

Question 16

avirulence gene

Answer 16

a gene that codes for a product in the pathogen

Question 17

effectors/elicitors

Answer 17

molecules that are produced by a pathogen which induce a response by the host

Question 18

resistance genes

Answer 18

a gene in the host that controls resistance/produces a produce (receptor) that recognizes the pathogen effector

Question 19

no gene resistance =

Answer 19

susceptibility

Question 20

susceptibility gene

Answer 20

a gene in the host that controls susceptibility

Question 21

non-host resistance

Answer 21

if pathogen has no pathogenicity genes, then plant/organism is a non-host/immune

Question 22

hypersensitive reaction

Answer 22

the expression of resistance of a host in response to attack by pathogen, often by death of invaded tissue

Question 23

who suggested the gene for gene relationship

Answer 23

H. H. Flor

Question 24

gene-for-gene theory

Answer 24

for every gene for resistance in the host, there is a corresponding gene for avirulence in the pathogen

Question 25

types of resistance in the host

Answer 25

qualitative and quantitative

Question 26

qualitative resistance in the host

Answer 26

either resistant or susceptible
usually controlled by a single or small # of genes (R genes)
less durable than quantitative

Question 27

quantitative resistance in the host

Answer 27

controlled by many genes
will protect plants from all races of the pathogen (more durable)
may not provide complete resistance