Silicon in mitigating biotic stresses in rice (Oryza sativa L.) – a review

Abstract

Silicon (Si), the second most abundant element in the earth's crust (28% of the total soil weight) is
assimilated solely as monosilicic acid. Absorption and accumulation of Si in different plants vary
from 0.1-10% on dry weight basis. It is beneficial or quasi-essential to graminaceous plants, such as
rice, wheat, barley, maize, sorghum, sugarcane, etc. Rice is a high Si accumulator plant and absorbs
on an average 150-300 kg of Si ha–1. It is probably the only element which is able to enhance the
resistance to multiple stresses. Providing appropriate amounts of Si to the plants cultivated in Si
deficient soils could considerably improve the rate of plant growth and its resistance against bioticand-
abiotic stresses. It has been found that, no lodging occurred in rice fields fertilised with calcium
silicate and more than 66% lodging was observed in untreated control fields. Application of calcium
silicate slag increased grain yield of rice by 10-17%. Silicon fertilizer shortens the leaf lesion caused
by bacterial leaf blight by 5-22% and leaf and neck blast was reduced by 50.5 and 26.8%, respectively.
Histosol soils in Florida amended with 5 t ha–1 of silicate slag resulted in 73-86% and 58-75% reduction
in blast and brown spot diseases, respectively, in rice with concurrent yield increases between 56-
88%. Silicon is as effective as conventional fungicides in controlling diseases of rice, such as leaf
scald (Monographella albescens), blast (Magnaporthe grisea), brown spot (Cochliobolus miyabeanus) and
grain discoloration. Silicon also suppresses diseases caused by bacteria and viruses. Silicon has
been found effective against insect-pests, such as stem borer, brown plant hopper, rice green-leaf
hopper and white backed plant hopper. Studies reported that use of silicate fertilizer reduced stem
borer incidence by 10-20% through enhanced effect of Si deposition in the plant tissues which acts
as a mechanical barrier against chewing by insects.