invit - Australasian Plant Pathology Society

Go to
Table of Contents
YIELD LOSS IN DURUM WHEAT IS RELATED TO PRE-PLANTING
CONCENTRATIONS OF FUSARIUM PSEUDOGRAMINEARUM DNA IN SOIL
M.L. Evans A and G.J. Hollaway B
A
SARDI, Adelaide. Email: marg.evans@sa.gov.au
B
DPI, Horsham.
ABSTRACT. This study explored relationships between pre-planting inoculum of Fusarium pseudograminearum and yield of crown
rot in durum wheat in south eastern Australia. Real-time quantitative PCR was used to measure F. pseudograminearum DNA
concentrations (inoculum) prior to planting in soil samples which included infected crop residues. Pre-planting inoculum and grain
yield were measured for seven field experiments (2005-2009) at one Victorian and two South Australian sites. As pre-planting F.
pseudograminearum DNA concentrations increased, grain yield decreased with significant relationships in all but two experiments
where combined September+October rainfall (COSR) was higher than the long term average. Yield losses of 6% to 8% occurred
with each doubling of inoculum where COSR was below average, but yield losses of only 1% to 3% occurred where COSR was
above average. This is the first time direct relationships between F. pseudograminearum DNA concentrations in soil samples taken
prior to planting and yield of durum wheat have been demonstrated. These relationships were consistent across experiments and
between states, which gives confidence that risk categories developed using pre-planting soil sampling and DNA technology will
have wide commercial applicability. The influence of increasing inoculum levels on yield and its moderation by COSR highlights the
need for multiple experiments conducted over a range of conditions when undertaking field research with crown rot.
INTRODUCTION
Crown rot, caused by F. pseudograminearum and F. culmorum,
affects all winter grown cereals and results in significant yield
losses in south eastern Australia. There are few in-crop
management options for crown rot, which makes it important for
growers to be able to select fields with low crown rot inoculum
when sowing high risk cereals such as durum wheat.
The suite of soilborne diseases detected and quantified by
PreDicta B TM (a commercial root disease testing service),
includes F. pseudograminearum and F. culmorum. However,
the similarity of relationships between pre-planting Fusarium
spp. DNA in soil samples and yield of cereals over a range of
climatic conditions and across regions has not been verified.
Demonstrating consistency in these relationships would lay the
foundation for improving the accuracy of crown rot risk
categories used in the PreDicta B TM service.
This study examines the relationships between pre-planting
concentrations of F. pseudograminearum DNA, spring rainfall
and yield of durum wheat.
MATERIALS AND METHODS
Experiments were located in Victoria (Longerenong 2007,
2009) and South Australia (Cambrai 2005; Hart 2008, 2009).
Minimal inoculum of soilborne cereal root diseases was present
at the sites and crown rot inoculum was artificially introduced up
to 5 years prior to this study.
Soil cores, including plant residues, were taken prior to
planting to a depth of 100 mm using an Accucore TM sampler.
QPCR assays based on rDNA (TaqMan TM ) probe sequences
were applied to the total DNA extracted from soil samples (each
sample being a composite of 24-40 soil cores). Disease incidence
(stems with basal browning and whitehead expression) data were
recorded but are not presented here.
Associations of yield (square root transformed) with preplanting
fungal DNA (log 10 + 1 transformed) were investigated
using linear correlations and simple linear regressions.
RESULTS AND DISCUSSION
As pre-planting concentrations of F. pseudograminearum DNA
in soil increased, yield of durum wheat decreased (Table 1). In
only two instances were the relationships not statistically
significant – both in experiments where combined
September+October rainfall (CSOR) was below the long term
average (Table 1). This is the first time such relationships have
been demonstrated under field conditions and emphasise the
need for keeping crown rot inoculum levels as low as possible in
commercial fields being sown to durum wheat.
These findings validate the use of pre-planting
concentrations of F. pseudograminearum DNA in soil for
prediction of the risk of yield loss from crown rot in commercial
fields. Development of robust risk categories for crown rot will
be the subject of a future publication.
Yield losses of 6% to 8% occurred with each doubling of
inoculum where COSR was below average, but yield losses of
only 1% to 3% occurred where COSR was above average (Table
1). The influence of increasing inoculum levels on yield and its
moderation by COSR highlights the need for multiple
experiments conducted over a range of conditions when
undertaking field research with crown rot.
Yield loss patterns in relation to CSOR were consistent
across experiments and between states (Table 1). This implies
that risk categories developed for crown rot should have
applicability across a wide area.
ACKNOWLEDGEMENTS
Funding by the Grains Research and Development Corporation.
Statistical analysis by Chris Dyson (SARDI).
Table 1. Relationships between pre-planting soil concentrations of DNA of Fusarium pseudograminearum and grain yield of
durum wheat in Victoria and South Australia, 2005-2009.
A
B
C
Location Year N A fungal DNA vs yield DNA doubles CSOR B (%)
Correlation coefficients, % Yield loss if soil Rainfall
Hart experiment 1 2008 28 -0.53** C 7 14
Hart experiment 2 2008 72 -0.54*** 8 14
Longerenong 2007 11 -0.87*** 6 35
Longerenong experiment 1 2009 12 -0.24 1 128
Longerenong experiment 2 2009 12 -0.40 1 128
Hart 2009 24 -0.44* 1 132
Cambrai 2005 72 -0.43*** 3 233
Number of soil samples (each sample being a composite of 24-48 soil cores).
Combined September and October rainfall presented as a % of the long term September and October rainfall for the site.
* P