Page 1
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
Page 2
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
Page 3
• 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
Page 4
Part 1: Some history1994: pre-planting fluazinam soil treatment reduced incidence of
powdery scab, increased tuber yield by 28% (weight/tuber)
Page 5
Total crop yield
+28%(increased weight/tuber)
% diseased
no chemical 19
fluazinam 6
tonnes ha-1
44.7
57.3
Page 6
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
Page 7
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%
Page 8
Soil moisture measurementsTime domain reflectometry
Page 9
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
Page 10
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
Page 11
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’
Page 12
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
Page 13
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
Page 14
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
Page 15
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
Page 16
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
Page 17
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)
Page 18
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
Page 19
2012/13 - Field survey sites
Page 20
Four fertiliser trials
No appreciable increase in yield
with doubled rates
Page 22
11 crops, 10 visits each (≈10 d intervals)(110 crop visits)
Page 24
Major yield-limiting factors
• Soilborne diseases
• Soil compaction
• Inefficient irrigation
• Weed infestations
• Variable plant emergence
Page 25
Rhizoctonia stem canker - all 11 crops
Page 26
Long term cropping,
potatoes 5 years previously
Long term grass,
no history of potatoes
Rhizoctonia stem canker
Page 27
-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
Page 28
Yield vs root vigour
Page 29
Spongospora root galls - five crops
Page 30
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
Page 31
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
Page 32
Yield-limiting factors
Page 33
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
Page 34
2014/15 - Three fields
Page 35
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
Page 36
The New Zealand Institute for Plant & Food Research Limited
Site 1
Page 37
Site 1: deep soil, flat field
Soil water content
Page 38
The New Zealand Institute for Plant & Food Research Limited
Site 2
Page 39
The New Zealand Institute for Plant & Food Research Limited
Site 2
Page 40
Site 2: stony soil, dense zone 250 mm, undulating
Soil water content
Page 42
Site 3: two soil types, stony, undulating
Soil water content
Page 43
Rhizoctonia stem canker
severity score
(5 ≡ 30% coverage)
Site 3
Site 2Site 1
Page 44
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
Page 45
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
Page 46
2015/16 - 18 fields, 25 ‘crops’(fresh market and processing)
Page 47
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
Page 48
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
Page 49
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
Page 50
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