L6 - Biological Flashcards
what are the problems associated w/ bio control
- toxicity of bio control ages
- evolution of resistance
- variability of success
example of variability of success
Pseumonas fluoresens only sucessful in 6/10 trails in combatting take all disease
biological organisms should be (4)
- good at colonising
- good at colonising rhizospshere
- adapted to a disturbed cultivated environment
- survive adverse conditions (prod spores/sclerotia)
in 2005 …. new bio agents for plant path reg
41 - majority true fungi/bacteria
Current products include (2)
- seed treatments - Short term
2. horticultural approches
5 mechanisms of Biological control
CAPIC
CAPIC
CAPIC
- competition
- antibiosis
- parasitism
- induction of host resistance
- cross-protection
adv of usign antibiosis
can detect in soil v little amounts
80mgha-1
Crown Gall dis is produced by……
Agrobacterium tumefaciens
Crown Gall bio agent is
Agrobacterium radiobacter strain K84
Crown Gall
antibiotic produced is
this causes
affects
Agrocin 84
inhibits leucyl tRNA synthesis
A. tumefacies only sensitive
-very specific
Crown Gall
issue w/ biocontrol
Res gene + product are on the same plasmid in A. radiobacter
–> can transfer to A. tum and it would be resistant.
Solve - mutant which cant transfer plasmid - K1026 - used in australia NOGALL
what is suppressive soils
the bacteria causing the disease is constantly present at low levels despite inoculum present and environment fav
Take All disease caused by…. + infects
Gaeumannomyces graminis
Wheat
Take all control by….
Pseudomonas fluorescens
strain Q8r1-96
Take all disease builds up in severity but levels off - expand
builds up year on year (gaeumannomyces graminis) but starts to decline at 4-5 years
famers should
a) short rotation
b) continuous wheat
example of suppressive soils with natural pseudomonas fluorescens levels building
Take all
antibiotic is
Pseudomonas fluorescens
2,4-DAPG
Take all
issue with antibiotic
- non specific 24DAPG can effect plants + animals
- affects multiple process
( good - can induce resistance in arabidopsis
Take all
antibiotic strains associate preferentially with specific plant species e.g.
has been modified how
wheat or Fusarium (peas)
into of PCA to Q8r1-96 strain - suppress root rot also
Damping off /Root rot caused by
Pythium ultimum
Damping off /Root rot control agent
Pseudomonas fluorescencs CHAO strain
Damping off /Root rot
produces
2,4-DAPG
+ pyoluteorin
Damping off /Root rot
results of engineering
engineered Pseudomonas fluorescencs CHAO strain to enhance pyoleutorin production:
- increased control of cucumber damping
BUT
strongly reduced growth of cress and sweetcorn in absence of pathogen
improvements of bio control (4)
- improve environ for bio agents
- obtain better control agents
- combo of organisms used
- combo w. fungicide
example of where bio and chem control together
De Curtis 2019
study used both on peaches and apricots against brown rot of stone fruits
