Lecture 12 - Insect plant pathogens

Question 1

biggest cause of crop loss

Answer 1

weeds
outcompete commercial crops or contaminate it

Question 2

what are the 2 other major cuases of crop loss

Answer 2

insect pests
microbial diseases (mostly fungi)

Question 3

disease triagnle- what 3 things must be in place for disease to occur

Answer 3

susceptible host
pathogen
favourable environemtn

Question 4

irish potatoe famine - context, pathogen?

Answer 4

relied on one type of potatoe for food (no genetic variance in the crop)
- phytophthera infestans caused crop loss

Question 5

what enzymes produced by pathogens are used to enter and disintegrate plant structure

Answer 5

celluloses
xylanases
pectinases

Question 6

what general effects might a toxin cause in plant

Answer 6

• interfere w/ cell functions
• disrupt metabolism, kill cells

Question 7

what could potentially alter plant environemnt to favour pathogen invasion and how

Answer 7

extracellular pathogen may release growth regulators
- intefere with plant hormones

Question 8

how are plant viral diseases transmitted

Answer 8

via insect vector
or grafting

Question 9

what are common symptoms of plant viral diseases

Answer 9

leaf spotting
chlorosis
stunted growth
ring spots
flower break
vein clearing

Question 10

main effects of plant viral disease

Answer 10

less crop yield
and crop value
but death of plants uncommon

Question 11

exmaple of positive plant virus

Answer 11

tulip breaking virus
valuable tulips

Question 12

what type of virus is citrus tristeza virus

Answer 12

ssRNA, helical symmetry
has lots of strains, each with diff virulence
and is transmitted by aphids

Question 13

how does CTV spread within plant

Answer 13

phloem

Question 14

cymptoms of CTV

Answer 14

clear veins
chlorosis
leaf cupping
might stunt growth
and if its rly bad, can kill trees

Question 15

what type of virus is tobacco mosaic virus

Answer 15

ssRNA
helical symmetry
moves via phloem

Question 16

what are symptoms of TMV

Answer 16

chlorosis
mosaic like mottling on leaf
rugosity (like bumps)
stunted growth
low yield
rarely causes death

Question 17

how might plant bact diseases cause plant to wilt

Answer 17

clogs vascula tissue ie phloem, so nutrients cant be spread

Question 18

what would agrobacterium tumifaciens cuase

Answer 18

crown gall tumours on plant

Question 19

what is blights

Answer 19

rapid destruction of plant tissue

Question 20

how does agrobacterium cause the tumours

Answer 20

integrates the T-DNA into the plant genome
which upregulates plant hormones
that cause formation of crown gall

Question 21

effects of agrobacterium

Answer 21

stunted growth, plant death

Question 22

what does bacillus thuringienensis cause

Answer 22

bact disease of insects
produces Bt toxin

Question 23

how is Bt toxin only insect toxin

Answer 23

highly insoluble usually
only activated in insect gut - high pH

Question 24

how does Bt toxin acts

Answer 24

forms pores in gut wall, insects stop eatingm dies
oe
bact gets into body cavity and causes lethal septicaemia

Question 25

how has Bt toxin been used by humans

Answer 25

gentically modified plants with Bt toxin
insect resistant

Question 26

what is entomophthorales

Answer 26

a fungal disease of insects
moslty host specific
its spores are used as a biopesticide

Question 27

2 other fungi that are used as biopesticides

Answer 27

metarhizium so
beauvaria bassiana

Question 28

what is nematophagy

Answer 28

carniverous trapping fungi

Question 29

how do these fungi form traps

Answer 29

when avialble nitrogen levels are low