New Zealand Journal of Crop and Horticultural Science abstracts
Effect of early blight (Alternaria solani) on healthy area duration
and healthy area absorption of potatoes (Solanum tuberosum) grown
in Canterbury, New Zealand with different nitrogen application and stress
from potato cyst nematode (Globodera rostochiensis)
S. F. A. Shah*
B. A. McKenzie
R. E. Gaunt†
Soil, Plant and Ecological Sciences Division
Lincoln University
Canterbury, New Zealand
John W. Marshall
New Zealand Institute for Crop & Food
Research Ltd
Private Bag 4704
Christchurch, New Zealand
C. M. Frampton
Christchurch School of Medicine
University of Otago
P.O. Box 4345
Christchurch, New Zealand
*Present address: New Zealand Institute for Crop & Food Research
Ltd,
Private Bag 4704, Christchurch, New Zealand. Email: Shahf@crop.cri.nz
†Deceased.
Abstract Two experiments were conducted over the 1995/96
and 1996/97 growing seasons, at Lincoln University and New Zealand Institute
for Crop & Food Research, Lincoln, Canterbury to assess the effects of
nitrogen and potato cyst nematode (Globodera rostocheinsis) on the
development of early blight epidemics. The objective was to measure effects
on photosynthetically active radiation (PAR) intercepted by crops under multiple
pest constraints, and also to compare the effect of early blight, nitrogen,
and potato cyst nematode on integrated values for healthy leaf area duration
(HAD) and healthy leaf area absorption (HAA). Epidemic development of early
blight was rapid in high nitrogen fertility plots and in plots with 30 nematode
eggs/ml of soil in 1995/96, but in 1996/97 neither nitrogen nor potato cyst
nematode significantly affected the epidemic development. In these trials
the intercepted PAR (HAA) was derived from the integral over time of green
leaf area index (GLAI) which was used as a measure of HAD. HAD and HAA were
derived from leaf area index (LAI) corrected by two methods, the percent
reflectance (PR) ratio or percent yellowing (PY). This paper explains the
detailed correction methods used and shows that LAI corrected with PR ratio
is the best way for calculating GLAI from a diseased crop, which can then
be used for calculating HAA. Early blight and potato cyst nematode significantly
reduced HAD and HAA whereas nitrogen significantly increased HAD and HAA
in both growing seasons. The effect of disease on HAD and HAA was not altered
by nitrogen or potato cyst nematode in both growing seasons.
Keywords early blight; Alternaria solani; potato
cyst nematode; Globodera rostochiensis; green leaf area index; radiation
interception; healthy area duration; HAD; healthy area absorption; HAA
H03031; Online publication date 17 March 2004; Received 24 March2003,
accepted 17 October 2003
New Zealand Journal of Crop and Horticultural Science, 2004, Vol. 32:
85-102
0014-0671/04/3201-0102 © The Royal Society of New Zealand 2004
PDF file of entire paper: Print-quality (350K) |
screen-quality (170K)
This year's abstracts |
Journal home page |
All abstracts |
Publishing home page
