Transcript TPP & Liberibacter in New Zealand Implications for seed potato certification Stephen Ogden Psyllid Coordinator Potatoes New Zealand.

TPP & Liberibacter in
New Zealand
Implications for seed
potato certification
Stephen Ogden
Psyllid Coordinator
Potatoes New Zealand
OVERVIEW
Psyllid & Liberibacter in New Zealand
 Industry impacts
 Management of TPP in seed crops
 Regulation of TPP/Liberibacter in seed potato
certification schemes

PSYLLID DISEASE COMPLEX

Psyllid disease complex:
 Potato
psyllid Bactericera cockerelli (2006)
 Candidatus Liberibacter solanacearum (2008)
Alone, TPP causes psyllid yellows
 TPP vectors Liberibacter

 Zebra
chip symptom in tubers
 Plant death
TOMATO POTATO PSYLLID (TPP)
- Laid on stalks, leaf margins
- 7 days to hatch
J Clark, Univ. Calif
Psyllid eggs
W Stepman, BCP Ltd
Lifecycle 15-30 days,
3-5 generations on potato
J Munyaneza, USDA
Psyllid nymph
- 3-4mm long
- Light yellow when emerge, 2-3 days brown or green
- Banded grey or black/white (5 days)
- Phloem feeding
J Munyaneza, USDA
Psyllid adult
LIBERIBACTER






Candidatus Liberibacter solanacearum
Transmitted by potato psyllid
Develops in phloem & psyllid
Interferes with transport of sugars into tubers
Leaf yellowing, curling, necrosis
Zebra chip in tubers
J Munyaneza, USDA
J Munyaneza, USDA
Photo (& top right) courtesy of J Anderson
TPP/LIBERIBACTER AFFECTED SEED
Field symptoms in process / table crops
 No impact

 Liberibacter
+ve seed line grew and processed
perfectly

Or…
 Weak
(hair) sprouts
 Multiple stems
 Numerous small tubers
 Chain tubers
2008-9

Major losses in the potato industry
 Est.
$47-56 million in losses 2008-9
 14% of industry value
 Crop losses
 Quality downgrades
2010-11 - INDUSTRY IMPACT ASSESSMENT

Aim – to accurately assess economic impact in
potatoes1,
 Production
impacts – yield, quality
 Control costs –insecticides, application costs
 Other– seed price, monitoring, compliance, market
access
1Economic
and business impacts of Potato Psyllid on the Potato industry. June 2011. Alan Kale,
ELAK Consultants.
THE SIZE OF THE PROBLEM

$120 million in losses to the potato industry in
last 3 seasons.
 $28
million in 2010-11
Additional costs to potato growers by region ($US/acre)
MANAGEMENT IN SEED PRODUCTON

Seed grown in isolation or in South Island
 Lower

TPP numbers
Regular application of agrichemicals
 Range
of chemistry registered (higher rates than for
aphids)
Crop monitoring
 All certified seed subject to virus field
inspections

 May
detect TPP/Liberibacter symptoms
RESEARCH – SEED TRANSMISSION

Early work suggested infected seed tubers
don’t grow
 Visible

symptoms in seed lots
Wen et al, 2009
 6%
of “ZC” infected seed germinated after 7 days
 96% of “ZC” free seed germinated after 7 days
 But…subsequent testing showed both lines had
~70% Liberibacter +ve
 Initial assessment was based on visual symptoms
SEED TRANSMISSION - US

US epidemiology study (Henne et al, 2010)
 18-44%
of “ZC affected” tubers sprouted
 Germination related to how badly affected by ZC
 TPP did not acquire Liberibacter from Lso +ve
plants grown from ZC affected seed
 ZC +ve seed planted into fields did not result in
spread of Liberibacter to neighbouring plants
SEED TRANSMISSION – NZ STUDIES

Pitman et al, 2011 – cage field trials
 Lso
+ve and –ve tubers (Q-PCR testing)
 With & without TPP (Lso –ve only)
 Replicated in two locations
The New Zealand Institute for Plant & Food Research Limited
The impact of Ca. Liberibacter infected
seed tubers on potato production
Nadine Berry, Shirley Thompson, Natasha Taylor, Peter Wright, Farhat
Shah, Melanie Walker, Sam Beard, Nina Jorgensen, Sarah Thompson,
Ian Scott, Ruth Butler, Andrew Pitman
The impact of seed tuber-borne Ca.
Liberibacter solanacearum in New Zealand
2010-2011 trial sites at Pukekohe and Lincoln
150 Lso-negative
150 Lso-positive
5 plants per cage (60 cages)
The New Zealand Institute for Plant & Food Research Limited
Sprouting of tubers
Sprouting of Lso-positive seed tubers was lower
(Pukekohe, p<0.001; Lincoln, p=0.008)
% of Tubers that Did Not Sprout
Non-sprouting tubers (X)
Lso negative
Lincoln
Lincoln 7/150 (4.7%)
35
Pukekohe
Pukekohe
11/150
Error bars:
95% confidence
limits (7.3%)
Lso positive
30
Lincoln 22/150 (14.7%)
25
Pukekohe 47/150 (31.3%)
% Not Emerging
40
20
15
10
5
0
Negative
Positive
Lso status
The New Zealand Institute for Plant & Food Research Limited
Rate of emergence and growth of potato
plants
The rate of growth from Lso-positive seed tubers was lower
Plant Emergence
100
Lincoln, -ve Lso
Lincoln, +ve Lso
Pukekohe, -ve Lso
Pukekohe, +ve Lso
50
Mean Plant Height
80
%Emerged Tubers
Plant Growth
60
60
40
20
40
30
20
10
0
0
2
3
4
5
Week
6
7
3
4
5
Week
The New Zealand Institute for Plant & Food Research Limited
6
7
Marketable yield of potatoes
Lso-positive seed tubers produced a lower marketable yield (p<0.001)
Marketable Yield 3.0
Lincoln
Pukekohe
Yield (kg)
2.5
Pukekohe
2.0
1.5
1.0
Marketable Numbers
16
0
25
Lincoln
100
0
25
100
Pukekohe
Number of Psyllids
-ve, No Psyllids
-ve, Psyllids Entire
-ve, Psyllids 1 week
+ve, No Psyllids
+ve, Psyllids Entire
+ve, Psyllids 1 week
Bars are LSD 5%
Number of Tubers
14
12
10
8
6
4
0
25
100
0
Number of Psyllids
25
100
The New Zealand Institute for Plant & Food Research Limited
Summary
• Tuber-borne Lso:
1.
2.
3.
4.
Reduced sprouting of tubers by approximately 23%
Caused significant loss in marketable yield (30 - 40%)
Does not influence specific gravity of harvested tubers
Does not cause widespread ZC symptoms in daughter
tubers
• Lso-negative TPP:
1. Did not influence tuber yield or ZC symptoms
The New Zealand Institute for Plant & Food Research Limited
Thresholds for diagnostic testing
A quantitative diagnostic is being used to establish thresholds
for commercial testing
Category
0
1
2
3
4
Titre range
0 (Lso Neg control)
<50 (including 0)
51 to 1000
1001 to 10000
>10001
Average marketable yield (Kg)
2.34
2.34
1.45
1.4
1.38
Total No. plants
121
256
141
126
15
The New Zealand Institute for Plant & Food Research Limited
CONCLUSIONS
 All
studies indicate germination and yield impacts
are related to Liberibacter titre or severity of ZC
symptoms in seed tubers
 Visually “ZC-free” tubers can be Lso +ve and result
in yield loss
1
2
3
REGULATION OF “ZC” IN SEED CERT


NZ has not moved to regulate at this stage
Not enough is known – what would be measured?


Psyllid numbers in crop (hot / cold)?
Symptoms?
What stage of crop?
 How often to inspect?
 Psyllid yellows vs Liberibacter?


Tubers?
How many tubers to sample and test?
 What does a positive mean – are all positives the same?
 Varietal differences?

REGULATION

In NZ seed crops are not “ZC” affected
 Merchant
testing of lines –ve to date
 Only problem year was in North Island seed in the
first season after Liberibacter detection
 Insecticide
programmes now manage this
 Short growing season cf process crops
 Research
being conducted to identify Lso
thresholds
 Q-PCR may provide rapid testing
 Sampling plans needed
REGULATION

In future it may be appropriate to include
Liberibacter in seed certification, but more
work is needed before it can be reliably
implemented.