New Zealand Journal of Crop and Horticultural Science abstracts
Effect of inoculum dose on infection of apple (Malus domestica)
flowers by Erwinia amylovora
R. K. Taylor
C. N. Hale†
W. R. Henshall
The Horticulture and Food Research
Institute of New Zealand Ltd
Private Bag 92 169
Auckland, New Zealand
email: chale@hortresearch.co.nz
†Corresponding author.
J. L. Armstrong
J. W. Marshall
New Zealand Institute for Crop and Food
Research Limited
Private Bag 4704
Lincoln, New Zealand
Abstract The effects of inoculum dose, flower age, and
climate (temperature, relative humidity, and rainfall) on the incidence of
fire blight following inoculation of apple (Malus domestica) flowers
with Erwinia amylovora were studied in an orchard. Disease symptoms
were only observed when populations of E. amylovora exceeded 106
colony-forming units (cfu) on flowers ≤4 days after budburst. The rate at
which these populations were reached depended on the climatic conditions
over flowering. Ten cfu of E. amylovora inoculated on flower stigmas
were capable of inciting fire blight in an orchard in which temperatures
above 15°C and high rainfall provided ideal conditions for bacterial
multiplication, infection, and subsequent expression of symptoms in flowers.
The results from this study may lead to insights into improved management
strategies and provide key information for phytosanitary risk assessments
for exports of commercial apple fruit.
Keywords Erwinia amylovora; fire blight; inoculum
threshold; infection
H03040 Received 17 April 2003; accepted 28 August 2003; Online publication
date 3 November 2003
New Zealand Journal of Crop and Horticultural Science, 2003, Vol. 31:
325-333
0014-0671/03/3104-0325 $7.00 © The Royal Society of New Zealand
2003
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