Agriculture Reference
In-Depth Information
Interaction between host and pathogen is significantly affected with
change in the gaseous composition of air that ultimately determines the
severity of the disease (Eastburn et al., 2011). The gaseous composition
may contribute to increase or decrease the level of disease for a said host-
parasite interaction. For example, increased concentration of CO
2
lead to
reduced epidemics under a wheat-pathosystem (Semenov, 2009) but in-
creased concentration O
3
enlarges the epidemics for a phyto-pathosystem
governed by
Botrytis cinerea
(Eastburn et al., 2011) which is contradictory
to a report where increased concentration of O
3
was claimed to inhibit
sporulation and germination in
B. cinerea
(Krause and Weidensaul, 1978).
Thin-walled fungi like
Rhizopus
,
Penicillium
,
Aspergillus
,
Trichoderma
,
etc. were susceptible to O
3
(Hibben and Stotzky, 1969), however, spores
of
Alternaria
and
Stemphylium
spp. did not affect with increased O
3
con-
centration having the thick-walled spore (Rich and Tomlinson, 1968). The
concentration of SO
2
has increased greatly over centuries, making this gas
as one of the most important air pollutant. This gas affects a phytopa-
thosystem in other way: it influences a disease by interfere the metabolic
activities of the plant. This gas is played a role as stimulus in production
of 'stress ethylene' (Pant, 2000), which finally leads to mango malforma-
tion—a mystery. Beside that the increased concentration of this noxious
gas has been associated with black-tip in mango (Ranjan and Jha, 1940).
These two problems causing reduced production of mango in many man-
go-growing pouches of Indian subcontinent.
Genes conferring resistance (R) are in general not effective at higher
temperature, for example, most R-genes of
P. recondita
-wheat pathosys-
tem (Kolmer, 1996). However, R-gene against wheat stripe rust (Yr36) is
effective at 25 to 35ºC but ineffective at lower temperatures (15ºC) and
thus become susceptible to
P. striiformis
f. sp.
tritici
infection (Uauy et
al., 2005). Deviation in temperature determines the virulence pattern of
the pathogen, has been proved in many phytopathosystems (Milus et al.,
2009; Webb et al., 2010). Isolates of
P. striiformis
f. sp.
graminis
collected
after year 2000 showed adaptation to a regime of warmer temperature and
causes significantly enlarged amount of epidemics in eastern Australia and
United States (Milus et al., 2009). In other quantitative analyzes, the post-
2000 isolates were found more aggressive for different monocyclic pro-
cesses. The changing pattern of temperature and future prediction is given
in
Fig. 10.4
.
