DEFENCE MECHANISM IN RICE AGAINST SHEATH BLIGHT CAUSED BY Rhizoctonia solani Kühn
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Date
2018
Authors
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Journal ISSN
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Indira Gandhi Krishi Vishwavidyalaya, Raipur
Abstract
The present investigation entitled “Defence mechanism in rice against
sheath blight caused by Rhizoctonia solani Kühn” were conducted in the
laboratory and fields of Department of Plant Pathology, ICAR-Indian Institute of
Rice Research, Rajendranagar, Hyderabad, 500030.
Rice is a most important cereal and is principle food for about 60% of the
world’s population. The production and productivity of rice is reduced by
numerous diseases caused by fungi, bacteria, virus, nematodes and other abiotic
Title of the thesis “Defence mechanism in rice against
sheath blight caused by Rhizoctonia
solani Kühn”
Full name of the student Puli Sasanka Roy
Major subject Plant Pathology
Name and Address of Major Advisor Dr. Anil. S. Kothesthane, Head and
Professor, Dept. of Plant Pathology, CoA,
IGKV, Raipur.
Degree to be Awarded M. Sc (Ag) in Plant Pathology
Signature of Student
Signature of Major Advisor
Date: _______________
Signature of Head of the Department
xiv
constraints. Rice sheath blight caused by Rhizoctonia solani Kuhn [telomorph:
Thanetophorous cucumeris (Frank) Donk] is one of the major biotic constraint
damaging rice production in India. In the present study, the differential behaviour
of R. solani within the different tolerant and susceptible rice plants during different
stages of infection. The R. solani hyphal behaviour within the host tissue was
distinctly different in the susceptible and tolerant cultivars of rice. The growth of
hyphae, formation of infection cushions, density of hyphae on leaf surface and
formation of microsclerotia were high on susceptible cultivar when compared with
the tolerant one. The correlation between trichomes and susceptibility of the plant
was studied. The numbers of trichomes are more (30.76%) on the tolerant cultivar
(Whazhuophek) when compared to susceptible cultivar (IR-50). The defence
responses of tolerant and susceptible rice were monitored using biochemical
analyses and expression analyses of selected defence related genes over a time
course during different infection stages. Defence systems were differentially
activated in tolerant and susceptible rice plants after inoculation with R. solani and
it accounted for the difference in disease severity (PDI) in the those varieties. The
pathogen R. solani induced Phenylalanine ammonia lyase (PAL), Superoxide
dismutase (SOD), Peroxidase (POX), Polyphenol oxidase (PPO) in tolerant
cultivars (Whazhuophek, Ngonolosa and Tetep) whereas in susceptible cultivars
(TN-1 and IR-50), it had suppressed POX and SOD enzymes. Distinct difference
was observed in activity of these enzymes in different cultivars at different times
of course. The enzyme activity was observed peaks at 24 and 48 hours post
inoculation mostly in all cultivars. The expression rate of selected defence related
genes in two cultivars i.e., Whazhuophek as tolerant and IR-50 as susceptible were
studied. The expression transcripts of defence related genes viz., PR-1, PR-2, PR-3,
PR-4, PR-5, PR-9, PR-10, PR-13, CHS, LOX, PAL and PPO were studied by
using quantitative Real-time PCR (qRT PCR). Results showed that the expression
of all genes in tolerant cultivar were higher than that of susceptible cultivar, post
inoculation. Significant differences were observed between these two cultivars.
These studies suggest that the roles of these defese mechanisms are more
significantly related to host-pathogen interaction.
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