Spongospora subterranea research in SA: Who, what, where and why?
Jacquie van der Waals
Department of Plant and Soil Sciences
University of Pretoria
@jacquievdw
Spongospora Workshop Sept 2019
Why study Spongospora subterranea f. sp. subterranea?(In South Africa)
Root infection →Disrupted root function
Root hyperplasia → Root galls → Disrupted root function
Tuber infection→ Powdery scab → Reduced quality / rejection of seed
Powdery Scab
Steadily increasing in incidence, severity and distribution over past decade in SA
• Underestimated and misdiagnosed
• Stigma related to disease
• Long term survival of resting spores in soil
• Intensification of potato production – limit of virgin soil available
• Use of susceptible cultivars
• Irrigation of the crop
Spongospora subterranea f. sp. subterranea has
increased in incidence, geographical or host range
Emerging diseasesEmerging infectious diseases (EIDs) are caused by pathogens that have
“(i) increased in incidence, geographical or host range;
(ii) changed pathogenesis;
(iii) newly evolved or
(iv) been newly discovered or recognized”1
1 Anderson et al. 2004
An emerging disease in South Africa
Spongospora subterranea f. sp. subterranea research in South Africa
Field trials
2019 Potato Pathology Programme @ UP Team
Not in photo: Ms Lindie Erasmus, Mr Joel Dube, Ms Lebo Lekota, Mr Robert Conrad, Ms Erika Botha, Ms Omphile Moche
• Optimal temperature and soil moisture for root infection
• Soil treatments
• Alternative hosts
• Cultivar screening
• Expression of disease response genes
• Genetic diversity of pathogen
• Wind dispersal of pathogen
Management options?
Research projects
Product Clanwilliam Sandveld 1 Sandveld 2 KZN NE Cape
Azoxystrobin X
Biologicals (various) TerraviteTrichoderma
MosblendTrichodermaVitaZyme
AlexinCrop BiolifeTrichoderma
Bacillus subtilisTrichoderma
Calcium cyanamide X X X
Dichloropropene & chloropicrin
X
Fluazinam X X
Mancozeb X X
Manganese complexes X
Metam sodium X X X X
Oxamyl X
Propineb X
Sulphur X
ZnO X
Untreated control X X X X X
Soil
Trea
tmen
ts
Pre
sen
ted
pre
vio
usl
y
Average powdery scab disease index at harvest per treatment
Disease index was calculated by multiplying disease incidence with mean disease severity.
REML analysis; p < 0.001
0
1
2
3
4
5
6
7a
b
ab
ClanwilliamTrial
Soil
Trea
tmen
ts
Pre
sen
ted
pre
vio
usl
y
Root galls mean disease index
Three plants per block, randomly selected, five weeks post emergenceREML analysis; p < 0.001
a
bc
cd
d0
0.020.040.060.08
0.10.120.140.16
CaC
N 3
00
pla
nt;
20
0
Co
ntr
ol
CaC
N 5
00
MeN
a
CaC
N 3
00
; 20
0
Gal
ls m
ean
ind
ex
Sandveld 1 Trial
Soil
Trea
tmen
ts
Pre
sen
ted
pre
vio
usl
y
Powdery scab lesions mean disease indexb
a a a a0
0.10.20.30.40.50.60.7
Co
ntr
ol
CaC
N 5
00
CaC
N 3
00
pla
nt;
20
0
CaC
N 3
00
; 20
0
MeN
a
Po
wd
ery
sca
b le
sio
n m
ean
in
dex
Twenty tubers per block, randomly selected at harvestREML analysis; p < 0.001
All treatments more effective than control
Soil
Trea
tmen
ts
Pre
sen
ted
pre
vio
usl
y
Root galls mean disease index
0
5
10
15
20
25
30
Co
ntr
ol
MeN
a 9
00
L/h
a 1
4d
bp
+Tr
ich
oP
lus
1w
ap
CaC
N 5
00
kg/
ha
10
db
p +
Mo
sble
nd
+ V
itaz
yme
1w
ap
MeN
a 9
00
L/h
a 1
4d
bp
CaC
N 3
00
kg/
ha
10
db
p +
20
0 e
mer
g
Mo
sble
nd
3 k
g/h
a +
Vit
azym
e 1
L/h
a 1
wap
Mo
sble
nd
5 k
g/h
a +
Vit
azym
e 1
L/h
a 1
wap
CaC
N 5
00
kg/
ha
10
db
p +
Tric
ho
Plu
s 1
wap
Tric
ho
Plu
s 7
50
g/h
a 1
wap
MeN
a 9
00
L/h
a 1
4d
bp
+M
osb
len
d +
Vit
azym
e 1
wap
CaC
N 5
00
kg/
ha
10
db
p
Me
an R
oo
t G
all I
nd
ex
a
b
bc
c
Three plants per block, randomly selected, five weeks post emergenceREML analysis; p < 0.001
Sandveld 2 Trial
Soil
Trea
tmen
ts
Pre
sen
ted
pre
vio
usl
y
Powdery scab lesions mean disease index
0
1
2
3
4
5
6
7
Co
ntr
ol
CaC
N 3
00
kg/
ha
10
db
p +
20
0em
erg
MeN
a 9
00
L/h
a 1
4d
bp
MeN
a 9
00
L/h
a 1
4d
bp
+Tr
ich
o 1
wap
MeN
a 9
00
L/h
a 1
4d
bp
+M
osb
len
d +
Vit
azym
e 1
wap
CaC
N 5
00
kg/
ha
10
db
p +
Tric
ho
Plu
s 1
wap
CaC
N 5
00
kg/
ha
10
db
p +
Mo
sble
nd
+ V
itaz
yme
1w
ap
CaC
N 5
00
kg/
ha
10
db
p
Tric
ho
Plu
s 7
50
g/h
a 1
wap
Mo
sble
nd
3 k
g/h
a +
Vit
azym
e1
L/h
a 1
wap
Mo
sble
nd
5 k
g/h
a +
Vit
azym
e1
L/h
a 1
wap
Mea
n p
ow
der
y sc
ab d
isea
se in
dex
All treatments more effective than control
a
b
Fifty tubers per block, randomly selected at harvestREML analysis; p < 0.001
Soil
Trea
tmen
ts
Pre
sen
ted
pre
vio
usl
y
0
0.2
0.4
0.6
0.8
1
1.2
Cro
p B
iolif
e
Ven
tum
see
d
Bio
cult
Zn M
ax M
n M
ax
Ale
xin
Tige
r Zn
Tig
er M
n
Flo
wab
le s
ulp
hu
r
Man
ager
Ven
tum
fu
rro
w
Mea
n r
oo
t ga
ll d
isea
se in
dex
b
ab
a
Root galls mean disease index
Three plants per block, randomly selected, five weeks post emergence
KZN Trial
Soil
Trea
tmen
ts
Pre
sen
ted
pre
vio
usl
y
0
50
100
150
200
250
Ven
tum
See
d
Cro
p B
iolif
e
Flo
wab
le S
ulp
hu
r
Bio
cult
Ven
tum
Fu
rro
w
Man
ager
Tige
r Zn
Tig
er M
n
Zn M
ax M
an M
ax
Ale
xin
Mea
n p
ow
der
y sc
ab d
isea
se in
dex
Powdery scab lesions mean disease index
No significant differences
Soil
Trea
tmen
ts
Pre
sen
ted
pre
vio
usl
y
Root galls mean disease index
0
10
20
30
40
50
60
Sere
nad
e
Man
coze
b
Flu
azin
am
Cym
oxa
nil
Co
ntr
ol
Am
ista
r in
fu
rro
w
Tri
cho
der
ma
An
trac
ol
Vyd
ate
Mea
n r
oo
t ga
ll d
isea
se in
dex
No significant differences
Three plants per block, randomly selected, five weeks post emergence
NE Cape Trial
Soil
Trea
tmen
ts
Pre
sen
ted
pre
vio
usl
y
1 1 1 2
2 43
1 43
3
33
33
2
0
20
40
60
80
100
120
140
160
Ch
alle
nge
r
Mar
kies
Ko
nsu
l
Sifr
a
Har
mo
ny
Val
or
Mo
nd
ial
Nic
ola
Fian
na
BP
1
Sava
nn
a
Alm
era
Ava
lan
che
Nec
tar
Kik
ko
Elec
tra
Me
an r
oo
t ga
llin
g D
I sco
res
Root gall disease indices for cultivars tested in four powdery scab field trials. Numbersabove bars indicate the number of trials the cultivar was planted in out of the four.
Cu
ltiv
ar s
cren
ing
Pre
sen
ted
pre
vio
usl
y
1 1 5 11 5
1 2 11 4
4 23 1 2
1
3
3
3
1
3
1
0
20
40
60
80
100
120
140
160
Eos
Ko
nsu
l
Fian
na
Lan
orm
a
Mar
kies
Val
or
Ch
alle
nge
r
Sifr
a
Div
a
Syn
erg
y
Mar
imb
a
Mo
nd
ial
Har
mo
ny
Ava
lan
che
Elm
on
do
BP
1
Nic
ola
Sava
nn
a
Kik
ko
Nec
tar
Elec
tra
Alm
era
Trio
mf
Po
wd
ery
sca
b le
sio
ns
DI s
core
s
Tuber lesion disease indices for cultivars tested in five powdery scab field trials. Numbers above bars indicate the number of trials the cultivar was planted in out of the five.
Cu
ltiv
ar s
cree
nin
g
Pre
sen
ted
pre
vio
usl
y
Root galls and powdery scab detected on potatoes planted in virgin soil
Wind dispersal of pathogen
Virgin and cultivated fields sampled
qPCR
0.56
16.49
6.02
33.12
1.130.05 0.00 0.21 0.00 0.01
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
Field 1 Field 2 Field 3 Field 4 Field 5 V1 V2 V3 V4 V5
Sss
DN
A q
uan
tity
ng/µ
l
Soil samples
Carmen Rensburg (MSc student)
Wind dispersal of pathogen
0.56
16.49
6.02
33.12
1.130.05 0.00 0.21 0.00 0.01
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
Field 1 Field 2 Field 3 Field 4 Field 5 V1 V2 V3 V4 V5
Sss
DN
A q
uan
tity
ng/µ
l
Soil samples
Implications:Sss may be spread by wind →Virgin fields may be contaminated with SssPre-plant soil testing can be done to assist with decision making
“We still do not know one thousandth of one percent of what nature has revealed to us.”Albert Einstein
