S. Salamati et Ha. Magnus, LEAF BLOTCH SEVERITY ON SPRING BARLEY INFECTED BY ISOLATES OF RHYNCHOSPORIUM-SECALIS UNDER DIFFERENT TEMPERATURE AND HUMIDITY REGIMES, Plant Pathology, 46(6), 1997, pp. 939-945
The infection efficiency and severity of leaf blotch on spring barley
inoculated with three pathotypes of Rhynchosporium secalis from centra
l Norway were studied under different temperature and humidity regimes
. Seedlings of the cultivar Arve were subjected to two constant temper
atures, 13 degrees or 18 degrees C. Dry periods of 8 h or longer befor
e or after a wet period of 4 h, carried out in the first 48 h postinoc
ulation, reduced disease severity assessed 16 days after inoculation.
The effect of dry periods of up to 24 h was nullified when plants were
subjected to high humidity for 48 h after the dry treatment. The dise
ase developed most rapidly when the wet period was 48 h and the temper
ature 18 degrees C. At or near the optimum temperature for R. secalis
(18 degrees C), leaf wetness duration as short as 2 h resulted in cons
iderable disease. Isolates reacted differently to temperature. The mos
t aggressive isolate caused severe disease irrespective of temperature
(56-70% of the leaf area infected); however, disease severity caused
by the least aggressive isolate was significantly higher at the optimu
m temperature compared with a lower temperature (13 degrees C). This i
nformation can facilitate evaluation of weather data in relation to pr
edicting leaf blotch for advisory purposes.