Mercado Financiero Intermediado
6.1.3. Entidades Prestadoras de Servicios Financieros
Richard E. Falloon{ XE "Falloon, R.E." }A,B, Denis CurtinA, Ros A. ListerA, Ruth C. ButlerA, Catherine L. ScottA and Nigel S. CrumpC
A
New Zealand Institute for Plant and Food Research Limited, PB 4704, Christchurch, New Zealand
B
Bio‐Protection Research Centre, PO Box 84, Lincoln University, Canterbury, New Zealand
C
DPI Victoria, Knoxfield Centre, Private Bag 15, Ferntree Gully Delivery Centre, Victoria 3156, Australia
INTRODUCTION
Powdery scab of potato tubers (Solanum tuberosum) is caused
by the plasmodiophorid pathogen Spongospora subterranea f.
sp. subterranea. The disease is important where potatoes are
grown under intensive management, as it causes severe
reductions in quality of seed and ware potatoes from affected
crops (1). The pathogen can also infect potato roots, causing
root galls and reducing plant growth (1). Manipulation of soil
nutrients could be part of integrated powdery scab
management. Nitrogen (N)‐containing amendments have been
shown to reduce (2) and increase (3) powdery scab in field‐
grown potatoes.
We present results from an experiment that aimed to determine
effects of different rates and types (nitrate or ammonium) of N
compounds on infection of potato plant roots by S. subterranea.
MATERIALS AND METHODS
The experiment was carried out in a glasshouse compartment
(17ºC ± 2ºC; 16 h light, 8 h dark). Tissue‐cultured potato
plantlets (cv. Iwa; very susceptible to powdery scab) were
planted into a 50:50 w:w mix of field soil and coarse sand (>1
mm) in plastic pots (11 cm diam., 680 ml capacity). The soil in
each pot was irrigated with deionised water (by weight) to 90%
water holding capacity three times each week for 8 weeks.
Two weeks after planting, treatments of three N compounds
(ammonium nitrate (NH4NO3), ammonium sulphate ((NH4)2SO4),
calcium nitrate (CaNO3)2.4H2O)) were each applied to separate
pots as solutions at five different rates, calculated to apply
equivalent amounts of N. The rates were 0.05, 0.10, 0.20, 0.40,
or 0.60 g N pot‐1, equivalent to 62.5, 125, 250, 500 and 750 kg N
ha‐1. At the same time the pots were each inoculated with
suspensions of S. subterranea sporosori (30,000 pot‐1). Two
control treatments of no added N with or without inoculum
were also applied. The experiment included 17 treatments
(three N compounds, five rates of each, plus two controls), and
was of randomised complete block design with seven replicates.
The plants were harvested 8 weeks after planting. Each plant
was carefully washed free of soil, the number of S. subterranea
root galls was counted and root dry weight (10 h at 70ºC)
determined. Data were transformed (square root) to stabilise
variances and analysed with ANOVA.
RESULTS AND DISCUSSION
Fig. 1 summarises data of severity of S. subterranea galling on
the roots of harvested plants. No galls were observed on
uninoculated plants, while plants from the nil N inoculated
treatment had a mean of 80.5 galls g‐1 root. All of the N
treatments reduced root galling. Increasing rates of N for both
ammonium sulphate and ammonium nitrate gave decreasing
numbers of root galls. For calcium nitrate, however, increasing
rate had little effect on root galling. At the three lowest rates in
N, of the three N‐containing compounds, ammonium sulphate
gave the greatest reduction in root galling.
These results indicate that ammonium‐N is more inhibitory to S. subterranea infection of potato roots than nitrate‐N. They also
suggest that increased powdery scab in the field after addition of
high rates of N fertiliser (3) were unlikely to be due to direct
effects of N on the pathogen, but may have been caused by
indirect host growth effects (e.g. increased root mass resulting in
increased amounts of zoospore inoculum).
N (g pot-1) 0.00 0.05 0.10 0.20 0.40 0.60 M ean g alls p er g roo t dry w eight 0 10 20 50 80 NH4NO3 (NH4)2SO4 Ca(NO3)2 Inoculated Control Uninoculated Control
Figure 1. Mean numbers of Spongospora subterranea root galls on
potato plants grown in pots treated with different amounts of N‐ containing compounds. Bar = LSD (P=0.05) for visual comparison of the means (square root transformed scale).
Ammonium‐N is usually converted to nitrate by soil micro‐
organisms soon after application (4). It is likely, therefore, that
the inhibitory effect of ammonium on S. subterranea occurred
during early host infection stages, possibly affecting zoospore
release from sporosori and/or infection of host roots.
These results suggest that ammonium‐N may usefully reduce S. subterranea infection of potato. This should be confirmed in
field evaluations in crops of potatoes grown in soil naturally
infested with the pathogen.
ACKNOWLEDGEMENTS
The NZ Foundation for Research, Science and Technology and
HAL (through the Australian Processing Potato Research
Programme) funded this research.
REFERENCES
1. Merz U, Falloon RE (2009) Review: powdery scab of potato—
increased knowledge of pathogen biology and disease
epidemiology for effective disease management. Potato Research
52: 17–37.
2. Falloon RE (2008) Control of powdery scab of potato; towards
integrated disease management. American Journal of Potato
Research 85: 253–260.
3. Falloon RE et al. (2007) Nitrogen fertiliser increases powdery scab incidence and severity; work in progress. 2nd European Powdery
Scab Workshop, Langnau, Switzerland, 29–31 Aug, 2007.
www.spongospora.ethz.ch/EUworkshop07/index.htm
5. Haynes RJ, Williams PH (1992) Changes in soil solution composition and pH in urine‐affected areas of pasture. Journal of Soil Science
Posters
66 Relationships between Spongosporascab in harvested subterranea potatoes DNA
in field soil and powdery
Farhat A. ShahA, Richard E. Falloon{ XE "Falloon, R.E." }A,B, Ros A. ListerA, Ruth C. ButlerA, Alan McKayC, Kathy Ophel‐KellerC and Ikram
KhanA
A
New Zealand Institute for Plant and Food Research, PB 4704, Christchurch, New Zealand
B
Bio‐Protection Research Centre, PO Box 84, Lincoln University, Canterbury, New Zealand
C
South Australian Research and Development Institute, GPO Box 397, Adelaide 5001, South Australia
INTRODUCTION
Powdery scab (caused by Spongospora subterranea f. sp.
subterranea) is an important disease of potato (Solanum
tuberosum). This disease is difficult to control, partly because S. subterranea can survive in soil for many years (1). Molecular
detection and quantification of the pathogen in soil are possible
components of disease management, to indicate pre‐planting S. subterranea inoculum levels and powdery scab risk (1).
We measured S. subterranea DNA levels in soil from a naturally
infested field at planting and powdery scab in subsequently
harvested tubers, over two growing seasons. Relationships
between pre‐planting soil DNA and disease on harvested tubers
were examined.
MATERIALS AND METHODS
The field area (0.36 ha) for this study had been previously used
as a trial during the 2006/07 growing season. Twelve treatments
(two cropping histories, three nitrogen fertiliser application
rates, two irrigation regimes) were applied to potatoes grown in
96 plots, each 5 × 5 m. The trial was of split split plot design with
eight replicates (2). The treatments resulted in different levels of
powdery scab in each plot (April 2007). During two subsequent
growing seasons (2007/08 and 2008/09), the same plots were
planted with cv. Agria (very susceptible to powdery scab) in
October, in rows (2 m long; eight tubers/row) centrally in the 5 ×
5 m plots. Soil samples were taken from each row at planting
and analysed for S. subterranea DNA, using quantitative PCR
techniques (3). Resulting tubers were harvested in April, washed
free of soil and individually assessed for powdery scab severity (0
= no disease, 1 = 5% tuber surface affected, 2 = 20%, 3 = 46%, 4 =
60%). Relationships between the S. subterranea DNA in soil and
powdery scab incidence and severity were explored graphically
and with linear correlations (Pearson’s r).
RESULTS AND DISCUSSION
2007/08 growing season. Powdery scab incidence in the plots
varied from 30 to 100%, and mean severity score varied from 0.3
to 2.7 (equivalent to 2 to 40% of tuber surface area affected).
The relationships between S. subterranea DNA quantities in soil
and powdery scab incidence (r = 0.53) and severity (r = 0.63) are
illustrated in Figure 1.
2008/09 growing season. Powdery scab incidence in the plots
varied from 4 to 83%, mean severity score varied from 0.04 to1.6
(equivalent to 0.2 to 16% of tuber surface area affected) and
amount of S. subterranea DNA varied from 58 to 1997 pg g‐1 soil.
The relationships between amount of DNA in soil and powdery
scab incidence and severity were very poor (r = 0.02 and 0.07
respectively).
This study has shown moderate to poor correlations between S. subterranea DNA in soil sampled at the time of sowing and
powdery scab in harvested tubers. These results were from a
field where soil DNA quantities and powdery scab were assessed
from 96 evenly spaced positions in a 0.36 ha area (≈ 270 samples
per ha.). In this study, where large pre‐planting quantities of S. subterranea DNA occurred in soil, DNA quantification did not
accurately predict incidence or severity of powdery scab in
harvested tubers. A % T u b er s i n fected 30 40 50 60 70 80 90 100 B
log10 pg DNA g-1 soil
1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 Me an s core 0.5 1.0 1.5 2.0 2.5
Figure 1. Relationships between S. subterranea DNA in soil at planting
and powdery scab incidence (A) and mean severity score (B) for potatoes grown in field plots.
ACKNOWLEDGEMENTS
The NZ Foundation for Research Science and Technology and
HAL (through the Australian Potato Research Program) funded
this research.
REFERENCES
1. Merz U, Falloon RE (2009) Review: powdery scab of potato—
increased knowledge of pathogen biology and disease
epidemiology for effective disease management. Potato Research
52: 17–37.
2. Falloon RE, FA Shah, et al. (2007) Nitrogen fertiliser increases
powdery scab incidence and severity; work in progress.
Proceedings of the 2nd European Powdery Scab Workshop.
Posters
3. Ophel‐Keller K, McKay A, Hartley D, Herdina, Curran J (2008)Development of a routine DNA‐based testing service for soilborne diseases in Australia. Australasian Plant Pathology 37: 243–253.
Posters
6 Bacterial canker of tomato: Australianmichiganensis diversity of Clavibacter michiganensis subsp
L.M. Forsyth{ XE "Forsyth, L.M." }, T. Crowe, A. Deutscher and L. Tesoriero
NSW Department of Primary Industries, Elizabeth Macarthur Agricultural Institute, Woodbridge Rd, Menangle 2568
INTRODUCTION
Bacterial canker of tomato is an important disease in Australian
tomato production, especially amongst the greenhouse industry.
The disease is caused by systemic vascular infection of the
bacteria Clavibacter michiganensis subsp. michiganensis (Cmm).
Canker infection can result in yield reductions of up to 100%.
Currently there are no effective chemical or biological control for
canker, the only effective methods are the quarantine and
eradication of infected material. The external symptoms of
bacterial canker have altered over the past decades. Whether
this is due to the use of newer tomato cultivars which react
differently to infection or due to the introduction of new genetic
strains of the bacteria is not known.
It is possible that there are new strains present in Australia since
Cmm can be seed borne and imported seed is generally
untreated since the relaxation of Australian quarantine
requirements in the early 1990s.
MATERIALS AND METHODS
Isolate collection. Isolates were collected from tomato growing
areas around Australia with a particular focus on greenhouse
tomatoes. International isolates have been sourced from the
Belgium culture collection (BCCM) and from America.
Genetic diversity. DNA was extracted from the isolates using the
Qiagen DNeasy kit, before quantification and dilution. DNA
fingerprinting was undertaken using the ERIC, BOX and REP PCR
(1). Further analysis of the genomic internal transcribed region
(ITS) was undertaken on all isolates using a combination of
sequencing and PCR‐RFLPs (2).
Pathogenic diversity. A range of tomato cultivars were used to
compare pathogenicity of Cmm isolates selected based upon the
genetic diversity results. Isolates were also screened against
other solanaceous crop plants commonly grown including
eggplant and capsicum.
RESULTS
Genetic diversity. Preliminary screening results using BOX, ERIC
and REP primers have revealed differences amongst Australian
Cmm isolates. Sequencing analyses of the ITS region of four
selected isolates has shown some base changes allowing the
development of PCR‐RFLP.
Pathogenic diversity. All tomato cultivars examined showed high
levels of susceptibility to Cmm, though symptom expression
appears to be cultivar dependent. Of the isolates examined the
majority were pathogenic, though there was at least one isolate
which appears to be avirulent.
Experiments examining a wider host range of Cmm revealed that
pathogenic isolates were able to infect the two capsicum
cultivars examined resulting in small localised lesions on the leaf
lamina where the inoculum was initially applied. No systemic
infection was observed within the capsicum plants. No
symptoms were observed on the eggplant cultivar used.
DISCUSSION
Cmm diversity. Early results from the DNA fingerprinting of the
Australian isolates of Cmm has revealed genetic diversity.
Further comparisons with international isolates and isolates
from field‐grown tomatoes will help understanding of whether
this diversity is reflected in the international diversity or
localised population drift potentially due to the high selection
pressure within the greenhouse environments.
Preliminary analyses of the genetic diversity of the avirulent
isolate has not revealed any distinct differences. The avirulent
isolate is being further tested using pulse field gel
electrophoresis to examine the presence of pathogenicity
conferring plasmids and virulence genes previously described
(3).
Only limited pathogenic diversity has been observed amongst
isolates of Cmm. Although there was some variation between
tomato cultivars in symptom expression, all tomato cultivars
assessed showed high levels of susceptibility to the majority of
isolates and eventually died due to application of Cmm. The
localised lesions which developed on the capsicum leaves did
not spread systemically in these experiments, implying that in a
controlled environment only direct contact with Cmm on the
leaves will lead to disease. Further testing using Cmm isolates
isolated from capsicum plants will be undertaken to determine
whether more severe disease could develop.
ACKNOWLEDGEMENTS
This work was funded by ACIAR, NSW DPI, Horticulture Australia
Ltd, AusVeg and the tomato consortium. Acknowledgement for
technical assistance from J. Collins, K. Turton, and S. Austin.
REFERENCES
1. Versalovich J, Schneider M, De Bruijn FJ, Lupski JR (1994) Genomic
fingerprinting of bacteria using repetitive sequence based
polymerase chain reaction. Methods in Molecular and cellular
biology 5, 25–40.
2. Fegan M, Croft BJ, Teakle DS, Hayward AC, Smith GR (1998) Sensitive and specific detection of Clavibacter xyli subsp. xyli,
causal agent of ratoon stunting disease of sugarcane, with a polymerase chain reaction‐based assay. Plant pathology, 47, 495– 504.
3. Meletzus D, Bermpohl A, Crier J, Eichenlaub R (1993) Evidence for
plasmid encoded virulence factors in the phytopathogenic
bacterium Clavibacter michiganensis subsp. michiganensis
NCPPB382. Journal of Bacteriology, 175, 2131–2136.