© Benaki Phytopathological Institute
Effect of solar radiation on
Rhynchosporium secalis
conidia
51
Table 3.
Mean scald disease severity (% of
the second leaf lamina showing symptoms)
17 days after the inoculation of three barley
(
Hordeum vulgare
) cultivars with
Rhynchos-
porium secalis
conidia, previously exposed
(Gs) or not exposed (G
NS
) to direct sunlight
for 8 h under field conditions.
Cultivar
Disease severity (%)
x
G
NS
G
S
WI2291
A89.3a
y
A77.57b
Arabi Abiad
B76.7a
B57.43b
Tadmor
C17.1a
C11.10b
x
Mean of three replicates.
y
Means preceded by different capital letters (column)
and followed by different lowercase letters (raw) are
significantly different at (
P
<0.05) by Newman-Keuls
test.
Figure 1.
Germination (%) of
Rhynchosporium secalis
conid-
ia exposed to UV-C light (254 nm) for different time periods at
room temperature (22-25°C). The UV irradiance at the level of
conidia was 3.2±0.7 Wm-
2
.
in killing most micro-organisms. This meth-
od has been used extensively in steriliza-
tion procedures with low energy germicid-
al lamps, which emit radiation principally at
254 nm. These results are consistent with re-
ports on other fungi, such as
Aspergillus car-
bonarius
,
Aspergillus niger
,
Cladosporium her-
barum
,
Penicillium janthinellum, Alternaria
alternata
and
Venturia inaequalis
(Aylor and
Sanogo, 1997; Valero
et al.,
2007).
Overall, the present study, which is part
of an on-going project on the epidemiolo-
gy of scald disease on barley in Syria, pro-
vides new information on the effect of solar
radiation on the survival of
R. secalis
conidia
during their aerial dispersal. Solar radiation
affects the viability of
R. secalis
conidia, and
thus, it is an important factor in their survival
while being airborne. This knowledge is im-
portant because dispersal limitation of the
R. secalis
population may drive very interest-
ing ecological dynamics. Models of airborne
dispersal of plant pathogens show that the
rate of long-distance dispersal depends
strongly on the longevity of propagules in
the atmosphere (Aylor,
2003
; Wilkinson
et
al.,
2012
). The influence of environmental
factors, such as cloud cover, wind, etc. on so-
lar radiation and their effect on conidia via-
bility need to be also considered.
The authors thank the Director General of
AECS and the Head of the Molecular Biology
and Biotechnology Department for their con-
tinuous support throughout this work.
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