-By- AMOL VIJAY SHITOLE

1. ROLE OF SILICA IN Plant DISEASE
MANAGEMENT
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2. INTRODUCTION
 Silicon is the second most abundant element in the earth crust. It is
readily taken up by plants and often present in relatively high
concentration of plant tissues.
 Silicon concentration in plant tissue some time even exceed the
concentration of nitrogen and potassium (Epstein, 1994) there for
silicon is often major constituent of plant tissue.
 Some plant such as many dicot are known as silicon non
accumulator and have tissue concentration of 0.5% or less
(Marschner 1995).
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3.  Other plants like wetland grasses are known as Si accumulator
because they tend to have relative high concentration of (5% or
higher) of tissue Si (Epstein, 1994).
 Si has been shown to be beneficial elements for many terrestrial
plants.
 The beneficial effects of adequate Si includes decreased
susceptibility to fungal pathogen and insects.
 It helps in decreasing abiotic stresses and increase growth in some
plants.
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4.  Silicon (Si) is the second most abundant mineral element in
soil comprising approximately 28% of the earth's crust.
 Silicon is deposited in the form of silica gel or biogenetic opal as
amorphous SiO2 n H2O in cell walls and intercellular spaces of root and
leaf cells as well as in bracts.
 Silicon also can be found in the form of monosilicic acid, colloidal silicic
acid, or organosilicone compounds in plant tissues. 4

5. History
 Isenosuke Onodera, Japanese plant nutrient chemist the first
researcher who suggested that Si was involved in rice resistance to
blast.
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Onodera, published a milestone paper entitled ‘Chemical studies on
rice blast disease’. This is the first report on Si research published in
a scientific journal of agronomy.

6.  Hayashi and Miyake and Ikeda also showed that the application of
Si increased resistance to blast as well as increased silica content
of rice.
 Kawashima first demonstrated under controlled conditions that
application of Si to rice plants increased resistance to blast as well
as increased Si content in rice.
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 This study focused on the uptake and deposition of Si in sugercane
as well as its severity of brown rust of sugercane caused by Puccinia
melanocephala.
 Both trials consisted of 9 treatments i.e. 100 ,200 ,300, 400,800,
1200, 1600, 2000 mg/ lit. potassium silicate, applied on a week for 8
weeks and Calmasil.
 A commercially available form of calcium silicate , applied at the
recommended dosage of 52 g / lit incorporated potting soil at
planting.

8. CONTENTS
 Introduction
 Rice Diseases.
 History.
 Role of silica in disease management
 Case studies
 Conclusion
 Future silicon research needs.
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9. Rice diseases
 Blast of rice co: Magnaporthe grisea
 Bacterial leaf blight co: Xanthomonas oryzae pv. oryzae
 Brown spot of rice co: Drechslera oryzae
 Grain discoloration of rice co: Bipolaris oryzae
 Stem rot of rice co: Sclerotium oryzae
 Neck blast of rice
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10. Grain discoloration
Neck blast
Brown spot
Leaf blast
Bacterial leaf blight
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Dry weight and silicon concentrations in shoots and roots of rice plants amended
with silicon (+Si) or not (−Si) and
inoculated with M. grisea (+M. grisea) or not (−M. grisea)

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Leaf blast symptoms

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17. Influence of calcium and mercuric fungicides alone and in combine blast
incidence and grain yield/ha
% of Neck blast Grain wt.( g/2.9m2)
Treatment 50kg/ha 75kg/ha 50kg/ha 75kg/ha
Silicon ( Si)* 12 11.2 1398.7 1415.7
Fungicide ( Fu)** 10.1 7.4 1302.0 1357.3
Si*Fu 1.7 2.5 1425.0 1504.7
Control 26.5 42.5 1018.0 1012.7
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18. • Calcium silicate applied at 2.25 ton/ha.
• ** Mercuric fungicides= phynel murcuric acetate:calcium carbonate
mixture (1:5) applied at 40kg/ha.
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19. Effect of propiconazole and silicon on brown spot
development
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Treatment Lesion no. per cm2 Brown spot severityb
Control 2.5ac 87a
Propiconazole (P) 2.0b 61b
Silicon 1.6c 37c
P+Si 0.6d 14d
a-area under disease progress curved, b-Brown spot severity based on 0-9
disease scale,where,0= no disease 9=76% or more leaf each numerical rating was
used for establishing differences between treatments, c- means followed by
different letter are significantly different based on FLSD P=0.05.

20. Si and greenhouse cucumber diseases
 Greenhouse cucumber are often grown in nutrient solution(
hydroponically) without added Si. This provides an excellent setting
for investigating the effects of Si on cucumber growth and disease.
 The effects of Si fertilization on greenhouse cucumber infection by
powdery mildew and Pythium spp. have been studied very throughly.
 Cucumber leaves were inoculated with known conidial concentration
( Menzies et.al., 1991 ).The investigation found that Si fertilization
reduce the leaf area covered by powder by as much as 98%.
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21.  The inoculated cucumber receiving Si fertilization were
productive as they uninoculated control in this study.
However, among the uninoculated (disease free ) plants,
those receiving Si fertilization did not differ significantly in
productivity from those not receiving Si fertilization.
 This seems to indicate that Si improve cucumber health
and productivity in the presence of pathogen.
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22.  Nutrient solution concentration was 100 to 200 ppm
SiO2 of potassium silicate.
 It reduces the root mortality,root decay and yield
losses on the plant inoculated with pythium ultimum.
 Furhtermore,in Si potassium silicate fertilized by
Pythium inoculate plants, root dry weights and number
of fruits ( especially high grade fruits)were significantly
higher than for Pythium inoculated plants without Si
fertilization ( Cherif and Belanger,1992).
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23. The effect of potassium silicate on
Phakopsora pachyrhizi on soybean
 Phakopsora pachyrhizi, the causal organism of soybean rust, is a
fungal pathogen causing significantly soybean losses throught the
world.
 To determine the effect of variouse concentration of potassium
silicate, two trials were conducted where Si was applied as a foliar
spray and a root drench.
 For the foliar treatment trials were follows: 0,1000,2000,4000mg/lit
Si, root drench (100mg/lit Si ) and Punch C (800ml/ha)+10000mg/lit
Si Punch C (400ml/ha ), Punch C ( 40oml/ha) +10000 mg/lit Si.
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24.  Si, Fly ( 95, 189, 378 kg/ha ) K Si slow release fertilizer (
59, 118, 236 kg/ha ) and Na Si slow release fertilizer ( 62, 124, 248
kg/ha ), applied twice during the season.
 For the foliar trial, Punch had a significantly lower area under the
disease progress curve and higher yield than all other treatment.
 All foliar Si application had a significantly lower AUDPC compare to
the untreated control.
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25.  AUDPC decreases of 20, 12 and 14% for 1000, 2000 and 4000mg/lit
Si and yield increases 12, 6 and 10% for 1000, 2000 and 4000mg/lit
Si were observed.
 For the drench trial, all Punch C treated plants had significantly lower
AUDPC and higher yield than all other treatments.
 AUDPC of Si treatments were not significantly different from that of
the .untreated control.
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 This study focused on the uptake and deposition of Si in sugarcane as well as its
effects on the severity of brown rust of sugercane , caused b y Puccinia
melanocephala.
 Both trials consisted of 9 treatments i.e. 100, 200, 400, 800, 1200, 1600, 2000
mg/lit potassium silicate, applied once a week and casmil, a commercially
available form of the calcium silicate, applied at doses 52g/lit incorporated in the
potting soil at planting.
 For the disease severity trials ,plants were naturally infected with P,melanocepha
by placing them in a tunnel with brown rust infected spreader plant.
Effect of silicon on rust of sugarcane

27.  From 3 weeks after planting,plants were rated
weekly for 5 weeks for percentage disease severity
using a rating scale.
 Percentage disease severity was reduced from 85%
in the control to 64% in plant treated with silicon at
200mg/lit.
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28. The effect of potassium silicate on the control of
Phakopsora pachyrhizi on soybean
 Phakospora pachyrhizi the causal organism of soybean rust a fungal
pahtogen causing significant yield losses throught out the world.
 To determine the effect of variouse concentration of silicon
(potassium silicate ) two trials were conducted where Si was
applied as a foliar spray and as root drench.
 For the foliar trials treatment were as follows 0,5000,10000mg/lit. Si
Punch C (800ml/ha), Punch C (800mg/lit)+10000mg/lit Si,Punch C
(400ml/ha) and 10000mg/lit Si.
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29. CONCLUSION
 Althought silicon is not consider to be an essential nutrient for plant.
But beneficial to many plants.
 Si has the potetial to significantely decrease the susceptibility of
certain plants to both abiotic and biotic disease.
 In plants such as rice, Si fertilization may even increase growth and
yield in addition to reducing disease severity.
 As we learn more about the important of silicon in plant physiology,
we may find more ways to use this important element in plant health
and disease resistance.
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30. FUTURE SILICON RESEARCH NEEDS
 Source of silicon and their management practices should be develop
and practices in integrated disease management programme for
those crop where Si has demonstrated to have positive effect.
 Some Si sources have residual activity that persist over time, raising
the possibility that applicaton need not be applied annually.
 There is need to find or develop cheaper and more efficient Si
sources.
 Effective, practical means of application and affordabe sources of Si
are needed for used row crop agriculture.
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