© Benaki Phytopathological Institute
Sakr
8
f.sp
.tritici
(Yang
et al.,
2003). Regarding the
rice–
M. oryzae
interaction, increased resis-
tance against the blast pathogen is char-
acterized by higher accumulation of gluca-
nase, peroxidase, polyphenol oxidase and
phenylalanine ammonia-lyase (Rodrigues
et
al.
, 2003, 2004, 2005; Cai
et al.
, 2008). Liang
et al.
(2005) found that enhanced peroxidas-
es, polyphenoloxidases and chitinases ac-
tivities due to silicon root application were
effective in reducing powdery mildew se-
verity in cucumber. Regarding
Cryptococcus
laurentii
-sweet cherry interaction, increased
polyphenol oxidase activity reduced disease
severity in fruit treated with 1% silicon (Qin
and Tian, 2005). Enhanced peroxidase activ-
ity in melon plants treated with sodium sili-
cate decreased incidence of pink rot caused
by
Trichothecium roseum
(Bi
et al.,
2006). In-
creased rice resistance due to silicon treat-
ment against the brown spot pathogen (
Bi-
polaris oryzae
) seems to be the result of
higher levels of chitinase and peroxidase
(Dallagnol
et al.,
2011). Enhanced peroxidase
and phenylalanine ammonia lyase activities
in sodium silicate-treated Chinese canta-
loupe decreased the severity of pink rot (
Tri-
chothecium roseum
) (Guo
et al.,
2007). Xavi-
er
et al.
(2011) reported that higher activities
of chitinases and peroxidases contributed to
the increase in wheat resistance to blast (
Py-
ricularia oryzae
). Increased activities of su-
peroxide dismutase, ascorbate peroxidase
and glutathione reductase in common bean
plants reduced severity of
Colletotrichum lin-
demuthianum
(Polanco
et al.,
2014). Schurt
et al.
(2014) found that the increased activ-
ities of phenylalanine ammonia-lyases, per-
oxidases, polyphenoloxidases and chitinas-
es in the leaf sheaths of rice plants supplied
with silicon led to the reduction in the prog-
ress of sheath blight lesions (
R. solani
). In-
creased activation of chitinase, superoxide
dismutase, peroxidase and
β-
1,3-glucanase
reduced the severity of powdery mildew
(
Podosphaera xanthii
) in melon plants (Dal-
lagnol
et al.,
2015). Perennial ryegrass grown
in silicon-amended soil exhibited greater
activities of peroxidase and polyphenol ox-
idase following infection by
Magnaporthe
oryzae
(Rahman
et al.,
2015). High activities
of superoxide dismutase, catalase, ascor-
bate peroxidase, glutathione reductase and
lypoxigenase contributed to the increase
in rice resistance to
Pyricularia oryzae
(Do-
miciano
et al.,
2015). In leaves of soybean
plants supplied with silicon, higher activi-
ties of chitinases,
β
-1-3-glucanases, pheny-
lalanine ammonia-lyases, peroxidases, and
polyphenol oxidases reduced the incidence
of target spot (
Corynespora cassiicola
)
(
For-
tunato
et al.,
2015).
4.2.2. Antifungal compounds
Antifungal compounds play important
role in plant fungal resistance (Fauteux
et al.
2005; Datnoff
et al.
2007; Van Bockhaven
et
al.
2013). Defense-related enzymes have an
important role in regulating the production
and accumulation of lignin, flavonoids, and
phytoalexins (Cai
et al.,
2009). Rodrigues
et
al.
(2005) reported the strong induction of
pathogenesis-related protein transcripts
following infection by
Magnaporthe grisea
,
which corresponded to an increase in the
concentration of lignin in rice plants. More-
over, Xavier
et al.
(2011) showed that the high
peroxidase activity following leaf blast in-
fection of wheat leaves supplied with silicon
was associated with an increase in the con-
centration of lignin. However, the biochemi-
cal pathways by which the phenolic metab-
olismmight mediate silicon-enhanced plant
resistance to fungi remains unclear (Fauteux
et al.,
2005; Datnoff
et al.,
2007; Van Bock-
haven
et al.,
2013). Silicon application induc-
es the production of antifungal compounds
after pathogen penetration of the epider-
mal cells (Cai
et al.,
2009).
Enhanced accumulation of phenolic
substances impeded the penetration of
Py-
thium ultimum
hyphae into the vascular sys-
tem of cucumber plants (Cherif
et al.,
1992).
Phenolics extracted from silicon-treated cu-
cumber plants displayed a strong fungistat-
ic activity against
Pythium
spp. (Cherif
et al.,
1994). Increased flavonoid phytoalexin agly-
cone rhamnetin in cucumber plants due to
silicon treatment decreased severity of pow-
dery mildew caused by
Podosphaera xanthii
