interactions between phoma koolunga didymella pinodes ......interactions between phoma koolunga,...
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Interactions between Phoma koolunga, Didymella pinodes and Phoma medicaginis var. pinodella, causal agents of ascochyta blight on field pea in
South Australia
Jenny Davidson (SARDI, University of Adelaide)&
Marzena Krysinska-Kaczmarek (SARDI)Herdina, Alan McKay(RDTS-SARDI)
&Eileen Scott (University of Adelaide)
FUNDED BY: South Australian Grains Industry Trust (SAGIT)
Field peas and ascochyta blight2009: 285,000 ha grown in Australia (47% crop in South Australia)
Value approx $100 million farm gate
Ascochyta blight (synonym blackspot)- major disease world wide
Affects all above ground parts and crown below the ground level
Annual losses ~ 15% of Australian pea crop
Can cause total failure of individual crop
▪are independent ▪exist in the same field ▪on the same plant
4 causal agents of ascochyta blight complex on field pea
Ascochyta pisiSplash borne conidiaNo known teleomorph(minor role in Australia)
Phoma medicaginis var. pinodellasplash borne conidia
Teleomorph only found once in laboratory conditions(Bowen et al. 1997, Mycological
Research 10: 80-84).
Ascochyta pinodesConsidered the major pathogenSplash borne conidia
Teleomorph: Didymella pinodesAirborne ascospores
Recently identifiedPhoma koolungaDavidson et al. 2009, Mycologia 101:120-129.Widespread in South Australia, limited distribution in Victoria and Western Australia. Similar symptoms to D. pinodes.
• P. koolunga newly recognised as an important component of the ascochyta complex on field pea in South Australia
• Appears to fit the same niche on field pea as the other fungal species
AIM
• Investigate interactions between Phoma koolunga; D. pinodes and P. medicaginis var. pinodella
What is the role of recently identified P. koolunga in ascochyta blight complex on field pea?
Competition on Potato Dextrose AgarZones of inhibition between paired pathogens including self paired colonies of P. koolunga.
a. D. pinodes c. P.medicaginis var. pinodella e. P. koolunga
b. P. koolunga d. P. koolunga f. P. koolunga
Interactions on amended Potato Dextrose AgarBroth filtrates produced for each pathogen
D. pinodes P. koolunga2 isolates
P. medicaginis var. pinodella
Sterile brothcontrol
25ml of each broth filtrate added separately to PDA
Each pathogen plated onto every type of amended agar
Culture growth measured at day 3 and day 7
Filtrate from P. koolunga inhibits growth of D. pinodes and P. medicaginis var. pinodella.
Filtrate sourceD. pinodes P. medicaginis
var. pinodellaP. koolunga a P. koolunga b
sterile broth-control 15.0 22.3 8.0 7.3D. pinodes 14.5 20.3 9.0 6.8P. medicaginis var. pinodella 15.0 23.3 8.8 7.3P. koolunga a (isolate DAR78535) 10.3 17.5 8.3 7.0P. koolunga b (isolate FT07006) 12.0 19.0 7.8 6.3LSDinteraction P(0.05) = 2.2
Effect of P. koolunga filtrate on colony growth of D. pinodes , P. medicaginis var. pinodella and P. koolunga
Diameter of colonies after 3 days (mm)
After removing cultures from filtrate normal growth is resumed = fungistasis.
Filtrate sourceD. pinodes P. medicaginis
var. pinodellaP. koolunga a P. koolunga b
sterile broth-control 44.0 52.8 24.8 23.3D. pinodes 42.5 51.5 20.5 21.8P. medicaginis var. pinodella 43.3 52.3 23.8 22.3P. koolunga a (isolate DAR78535) 43.3 50.0 20.5 22.8P. koolunga b (isolate FT07006) 43.3 52.3 22.8 23.5
mean 43.3 51.8 22.5 22.7LSDinteractionP(0.05) = not significant
Effect of removing P. koolunga filtrate from colonies of D. pinodes , P. medicaginis var. pinodella and P. koolunga
Diameter of colonies after 7 days (mm)
Interaction of pathogens in planta
Inoculated in pairs onto same leaf in controlled conditions
Lesion size by D. pinodesgreater than lesions by the two Phoma species.
No interaction in lesion size
Interaction of pathogens in planta - DNA quantification per leaf
0
2
4
6
8st
erile
aga
r**
D.p
inod
es
P.m
edic
agin
isva
r. p
inod
ella
P. k
oolu
nga
DAR
7853
5
P. k
oolu
nga
FT07
006
ster
ile a
gar*
*
D.p
inod
es
P.m
edic
agin
isva
r. p
inod
ella
P. k
oolu
nga
DAR
7853
5
P. k
oolu
nga
FT07
006
D. pinodes* P.medicaginis var. pinodella*
Log
(fg
DN
A D
pPm
p) p
er le
af a
t 7 d
p.i.
Quantity of DNA of D. pinodes and P. medicaginis var. pinodella is reduced in presence of P. koolunga
Interaction of pathogens in planta -DNA quantification per leaf
-Quantity of DNA of P. koolunga was not reduced by co-inoculation
0
2
4
6
8ste
rile
agar
**
D.p
inod
es
P.m
edic
agin
isva
r. pi
node
llaP.
koo
lung
aD
AR78
535
P. k
oolu
nga
FT07
006
steril
e ag
ar**
D.p
inod
es
P.m
edic
agin
isva
r. pi
node
llaP.
koo
lung
aD
AR78
535
P. k
oolu
nga
FT07
006
P. koolunga DAR78535* P. koolunga FT07006*Log
(fg D
NA
P. k
oolu
nga)
per
leaf
at 7
d p
.i.
Interaction of pathogens on leaf discs -Detached leaf discs floating on sterile RO water
-Measured lesion size and quantified DNA
• no interactions for DNA
• Interactions for lesion size
*denotes isolate which caused lesion measured** denotes co-inoculated isolate or sterile water for controls.
Interaction of pathogens on leaf discs – lesion size
0
5
10
15
D. p
inod
es**
P.m
edic
agin
isva
r. pi
node
llaP.
koo
lung
aD
AR78
535
P. k
oolu
nga
FT07
006
RO w
ater
D. p
inod
esP.
med
icag
inis
var.
pino
della
P. k
oolu
nga
DAR
7853
5P.
koo
lung
aFT
0700
6RO
wat
er
D. p
inod
esP.
med
icag
inis
var.
pino
della
P. k
oolu
nga
DAR
7853
5P.
koo
lung
aFT
0700
6RO
wat
er
D. p
inod
esP.
med
icag
inis
var.
pino
della
P. k
oolu
nga
DAR
7853
5P.
koo
lung
aFT
0700
6RO
wat
er
D. pinodes* P.medicaginis var.pinodella*
P. koolungaDAR78535*
P. koolunga FT07006*
Lesi
on d
iam
eter
(mm
)
7 d p.i. on leaf discs on sterile waterLesion diameter of D. pinodes and P. medicaginis var. pinodellareduced compared to controls in presence of P. koolunga isolate DAR78535 or self
Lesions size of P. koolunga isolate DAR78535 was increased in presence of P. medicaginis var. pinodella or if self paired.
Summary
• This study demonstrated interactions between the three ascochyta blight fungal species resulting in antagonism, including self antagonism.
• P. koolunga was not self antagonistic nor affected by co-inoculation with the other species.
• P. koolunga is slower growing but had fungistatic effects on the other causal pathogens.
• Anomalies possibly due to environmental effects of leaf discs.
• Further studies are warranted into the potential of fungistatic metabolites produced by P. koolunga.