Lecture 12 - Insect plant pathogens Flashcards
biggest cause of crop loss
weeds
outcompete commercial crops or contaminate it
what are the 2 other major cuases of crop loss
insect pests
microbial diseases (mostly fungi)
disease triagnle- what 3 things must be in place for disease to occur
susceptible host
pathogen
favourable environemtn
irish potatoe famine - context, pathogen?
relied on one type of potatoe for food (no genetic variance in the crop)
- phytophthera infestans caused crop loss
what enzymes produced by pathogens are used to enter and disintegrate plant structure
celluloses
xylanases
pectinases
what general effects might a toxin cause in plant
- interfere w/ cell functions
- disrupt metabolism, kill cells
what could potentially alter plant environemnt to favour pathogen invasion and how
extracellular pathogen may release growth regulators
- intefere with plant hormones
how are plant viral diseases transmitted
via insect vector
or grafting
what are common symptoms of plant viral diseases
leaf spotting
chlorosis
stunted growth
ring spots
flower break
vein clearing
main effects of plant viral disease
less crop yield
and crop value
but death of plants uncommon
exmaple of positive plant virus
tulip breaking virus
valuable tulips
what type of virus is citrus tristeza virus
ssRNA, helical symmetry
has lots of strains, each with diff virulence
and is transmitted by aphids
how does CTV spread within plant
phloem
cymptoms of CTV
clear veins
chlorosis
leaf cupping
might stunt growth
and if its rly bad, can kill trees
what type of virus is tobacco mosaic virus
ssRNA
helical symmetry
moves via phloem
what are symptoms of TMV
chlorosis
mosaic like mottling on leaf
rugosity (like bumps)
stunted growth
low yield
rarely causes death
how might plant bact diseases cause plant to wilt
clogs vascula tissue ie phloem, so nutrients cant be spread
what would agrobacterium tumifaciens cuase
crown gall tumours on plant
what is blights
rapid destruction of plant tissue
how does agrobacterium cause the tumours
integrates the T-DNA into the plant genome
which upregulates plant hormones
that cause formation of crown gall
effects of agrobacterium
stunted growth, plant death
what does bacillus thuringienensis cause
bact disease of insects
produces Bt toxin
how is Bt toxin only insect toxin
highly insoluble usually
only activated in insect gut - high pH
how does Bt toxin acts
forms pores in gut wall, insects stop eatingm dies
oe
bact gets into body cavity and causes lethal septicaemia
how has Bt toxin been used by humans
gentically modified plants with Bt toxin
insect resistant
what is entomophthorales
a fungal disease of insects
moslty host specific
its spores are used as a biopesticide
2 other fungi that are used as biopesticides
metarhizium so
beauvaria bassiana
what is nematophagy
carniverous trapping fungi
how do these fungi form traps
when avialble nitrogen levels are low
