The New Zealand Institute for Plant & Food Research Limited
Diseases caused by
Spongospora subterranea implicated
as components of sub-optimum
potato yields in New Zealand
Richard Falloon, Sarah Sinton, Farhat Shah, Steven Dellow,
Alexandre Michel, Craig Tregurtha & Hamish Brown3rd International Powdery Scab Workshop
Einsiedeln, Switzerland, 17-21 July 2014
New Zealand Institute for Plant & Food Research
Acknowledgements
Collaborating researchers:Dr Denis Curtin, Ros Lister, Dr Ruth Butler, Russell Genet,
Dr Mark Paget, Dr Ueli Merz
Plant pathology, Soil science, Agronomy, Plant breeding,
Biometrics
Funding agencies:
NZ Ministry for Business, Innovation and Employment
Potatoes New Zealand
Foundation for Arable Research
NZ Ministry of Agriculture & Fisheries Sustainable Farming Fund
McCain Foods Grower Group
NZ Institute for Plant & Food Research
Trimble Agricultural Research (Travel) Fellowship
• Part 1: Spongospora root diseases (Some history)
(summary of experimental evidence)
• Part 2: Multi-year field evaluations (“Yield gap”)
• Conclusions
Falloon, Merz, et al. (2016).
Plant Pathology 65: 422-434
Part 1: Some history1994: pre-planting fluazinam soil treatment reduced incidence of
powdery scab, increased tuber yield by 28% (weight/tuber)
Total crop yield
+28%(increased weight/tuber)
% diseased
no chemical 19
fluazinam 6
tonnes ha-1
44.7
57.3
Some history1994: pre-planting fluazinam soil treatment reduced incidence of
powdery scab, increased tuber yield by 28% (weight/tuber)
2005: Field-grown potato plants inoculated with S. subterranea had reduced
tuber yields, and reduced water use.
cv. Iwa
Plant parameters at harvest
Mean wgt
(kg) tubers
per plant
Mean no.
tubers per
plant
Mean wgt
(g) per
tuber
No inoculum 2.93 12.1 242
Inoculum 1.70 9.0 188
change -42% -26% -22%
Soil moisture measurementsTime domain reflectometry
Sample Date
7-Nov 21-Nov 5-Dec 19-Dec 2-Jan 16-Jan 30-Jan 13-Feb 27-Feb
Me
an
wa
ter
use
dif
fere
nce
fro
m a
ve
rag
e (
%)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
� � � � � � � � � �
UninoculatedInoculatedIrrigation�
Rain
Water use
Some history1994: pre-planting fluazinam soil treatment reduced incidence of
powdery scab, increased tuber yield by 28% (weight/tuber)
2005: Field-grown potato plants inoculated with S. subterranea had reduced
tuber yields, and reduced water use.
2011: Greenhouse trial; S. subterranea reduced root function and
growth of eight cultivars, with different susceptibilities to tuber
powdery scab
Glasshouse experiment
• Plant parameters
• Water use
• Spongospora severity
•Eight cultivars uninoculated
or inoculated with S. subterranea
• Very resistant‘Gladiator’, ‘Moonlight’ ‘Red Rascal’
• Moderately resistant‘Russet Burbank’, ‘Ranger Russet’,
‘Umatilla Russet’
• Very susceptible‘Iwa’, ‘Asterix’
Shoot Dry Weight
Gladiat
orMoonlig
htRed
Ras
cal
Ranger
Russ
etRuss
et B
urban
kUm
atilla
Russ
et Iwa
Aster
ix
g
1.21.41.61.82.02.22.42.62.8
V. Resistant Mod. Resistant V. Susceptible
UninoculatedInoculated
Bar is LSD 5%
Plant growth
Root function
Iwa
Days after planting
0 10 20 30 40 50
Wat
er u
se (
g)
0
5
10
15
20
25
↑↑↑↑ Inoculation
Ranger Russet
Days after planting
0 10 20 30 40 50
Wat
er u
se (
g)
0
5
10
15
20
25
↑↑↑↑ Inoculation
Russet Burbank
Days after planting
0 10 20 30 40 50W
ater
use
(g
)0
5
10
15
20
25
↑↑↑↑ Inoculation
Asterix
Days after planting
0 10 20 30 40 50
Wat
er u
se (
g)
0
5
10
15
20
25
↑↑↑↑ Inoculation
un-inoculatedinoculated
Umatilla Russet
Days after planting
0 10 20 30 40 50
Wat
er u
se (
g)
0
5
10
15
20
25
↑↑↑↑ Inoculation
Gladiator
Days after planting
0 10 20 30 40 50
Wat
er u
se (
g)
0
5
10
15
20
25
↑↑↑↑ Inoculation
Moonlight
Days after planting
0 10 20 30 40 50
Wat
er u
se (
g)
0
5
10
15
20
25
↑↑↑↑ Inoculation
Red Rascal
Days after planting
0 10 20 30 40 50
Wat
er u
se (
g)
0
5
10
15
20
25
↑↑↑↑ Inoculation
Final Water Use
Gladiat
orMoonlig
htRed
Ras
cal
Ranger
Russ
etRuss
et B
urban
kUm
atilla
Russ
et Iwa
Aster
ix
g
8
10
12
14
16
18
20
22V. Resistant Mod. Resistant V. Susceptible
UninoculatedInoculated
Bar is LSD 5%
Root function
Root galls
Galls/g Root Dry Weight
Gladiat
orMoonlig
htRed
Ras
cal
Ranger
Russ
etRuss
et B
urban
kUm
atilla
Russ
et Iwa
Aster
ix
Gal
ls/g
50
100
150
200
250
300
350
400
450 V. Resistant Mod. Resistant V. Susceptible
Spongospora root infection
• This pathogen adversely affects host plant
growth and productivity
• Deleterious effects occur, both in tuber-
resistant and tuber-susceptible cultivars
• Disrupted root function, root galling and
tuber powdery scab are separate diseases
Part 2: The “Yield Gap” projects
• Grower initiated
• Potato yields becoming uneconomic
• Average yields 45 to 60 t ha-1
• Potential yields >90 t ha-1
(as shown using validated computer-based
crop growth model)
Multi-year field evaluations
• Three growing seasons:
• 2012/13, 2014/15 and 2015/16
• Multiple crops (processing and fresh market)
• Detailed surveys
• Multiple samplings within each crop
• Assessment of yield-limiting factors
2012/13 - Field survey sites
Four fertiliser trials
No appreciable increase in yield
with doubled rates
11 crops, 10 visits each (≈10 d intervals)(110 crop visits)
diseasedhealthy
Major yield-limiting factors
• Soilborne diseases
• Soil compaction
• Inefficient irrigation
• Weed infestations
• Variable plant emergence
Rhizoctonia stem canker - all 11 crops
Long term cropping,
potatoes 5 years previously
Long term grass,
no history of potatoes
Rhizoctonia stem canker
-30
-25
-20
-15
-10
-5
0
5
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190
He
igh
t fr
om
to
p o
f ri
dg
e (
cm
)
Distance from centre of ridge (cm)
Potato bed profiles - Potato Yield Gap Project
Wheel track on left, bed furrow on right
Site 7
Seed depth
-30
-25
-20
-15
-10
-5
0
5
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190
He
igh
t fr
om
to
p o
f ri
dg
e (
cm
)
Distance from centre of ridge (cm)
Potato bed profiles - Potato Yield Gap Project
Wheel track on left, bed furrow on right
Site 8
Seed depth
Soil compaction
Yield vs root vigour
Spongospora root galls - five crops
Inefficient irrigation
0
10
20
30
40
50
60
70
80
Irrigationmissed
Irrigationnormal
Irrigationmissed
Irrigationnormal
Crop 6 Crop 6 Crop 1 Crop 1
Fre
sh t
ub
er y
ield
(t/
ha)
No irrigation Irrigated
Two crops
Weeds(Solanum spp.)
0
10
20
30
40
50
60
70
80
90
100
weeds weed-free
Crop 11 Crop 11
Fre
sh t
ub
er y
ield
(t/
ha)
One crop
Yield-limiting factors
2012/13 crop yields
0
10
20
30
40
50
60
70
80
90
100
1 2 3 4 5 6 7 8 9 10 11
Ma
rke
tab
le Y
ield
(t/
ha
)
Site
Potential
Field
2014/15 - Three fields
The New Zealand Institute for Plant & Food Research Limited
Eight sites in each crop
• Soil water measurements
• Regular (3 week intervals) crop sampling
and disease assessments
• Crop yields
The New Zealand Institute for Plant & Food Research Limited
Site 1
Site 1: deep soil, flat field
Soil water content
The New Zealand Institute for Plant & Food Research Limited
Site 2
The New Zealand Institute for Plant & Food Research Limited
Site 2
Site 2: stony soil, dense zone 250 mm, undulating
Soil water content
Site 3
Site 3: two soil types, stony, undulating
Soil water content
Rhizoctonia stem canker
severity score
(5 ≡ 30% coverage)
Site 3
Site 2Site 1
Spongospora root and stem galls
0
2
4
6
8
10
12
14
16
18
20
4-N
ov
-14
21
-No
v-1
4
10
-De
c-1
4
7-J
an
-15
3-F
eb
-15
3-M
ar-
15
10
-No
v-1
4
21
-No
v-1
4
10
-De
c-1
4
7-J
an
-15
2-F
eb
-15
3-M
ar-
15
1-D
ec-
14
23
-De
c-1
4
19
-Ja
n-1
5
17
-Fe
b-1
5
23
-Ma
r-1
5
Perry Pye Tayler
Sp
on
go
spo
raro
ot
ga
lls/
pla
nt
Spongospora (root galls)
Site 3Site 1 Site 2
Site 3: stony soil, Rhizoctonia stem canker,
Spongospora root galls
0
10
20
30
40
50
60
70
80
90
100
8 Oct 28 Oct 17 Nov 7 Dec 27 Dec 16 Jan 5 Feb 25 Feb 17 Mar
Tub
er
fre
sh w
eig
ht
(t/h
a)
Potential
1
2
3
4
5
6
7
8
Plot av
36 t/ha yield loss
2015/16 - 18 fields, 25 ‘crops’(fresh market and processing)
0
2
4
6
8
10
12
14
16
18
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Crops
Rhizoctonia stem canker severity
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Crops
Spongospora root gall severity
0.0
0.5
1.0
1.5
2.0
2.5
3.0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Crops
Powdery scab severity
1.0 = 5% tuber surface
affected
Conclusions• Spongospora root diseases reduce potato plant
growth and productivity (Part 1)
• Soilborne diseases are key causes of sub-optimum
potato yields in New Zealand
• Spongospora root diseases are commonly severe in
New Zealand (processing) potato crops
• Spongospora root galling has caused widespread
occurrence of these diseases
• Spongospora diseases are important causes of yield
reductions - effective management urgently required
Other diseases
Rhizoctonia,
black dot, common scab, Sclerotinia
Other yield limiting factors