Antiphytopathogenicity of Bioagents and Expression Anlysis of Selected Defence Genes in Rice in Presence of Actinobacteria and Rhizoctonia solani
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Date
2013
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UAS, Dharwad
Abstract
A total of fifty bioagent isolates comprising Trichoderma, pseudomonad, PPFM and
actinomycete spp., were screened against rice sheath blight pathogen Rhizoctonia solani
under in vitro condition and potent isolates were selected for in vivo assay. Five potent
isolates from each of the biocontrol agent was further evaluated against R.solani under
glasshouse condition. Of the fifteen efficient bioagent isolates evaluated, combined treatment
of Actinomycete isolate (IABT-A7) was promising with reduced disease parameters, lesion
length and number of dried leaves and enhanced the plant growth parameters viz., the plant
height, number of tillers, root length, root biomass. Potential actinomycete (IABT-A7) isolate
was identified as Actinopolymorpha spp., through Amplified rDNA Restriction Analysis
(ARDRA).
Expression of the key genes involved in Induced Systemic Resistance (ISR) and
Systemic Acquired Resistance (SAR) were analysed by real-time PCR. Gene expression and
quantum of expression was profiled at different time intervals 24 hr, 48 hr,72 hr and 120 hr
after infection of pathogen from treatments viz., seed treatment of IABT-A7, combined
treatment of IABT-A7 (seed+soil+foliar),only bioagent (IABT-A7) treatment, treated control
(only pathogen) and healthy plant. Jasmonic Acid (JA) pathway related genes, OsAOS2,
OsJMT1, OsJAMYB showed the differential expression in all the treatments and at all time
intervals over the treated control. ET biosynthesis gene, OsERF1 was up regulated in all
treatments at 48 hr, 72 hr and 120 hr over treated control. The relative up regulation of these
genes was highest in combined treatment over control. OsPR1b, a key gene for SAR pathway
was up regulated in only pathogen treated samples and up regulated up to 12 fold at 48 hr.
The master regulator defence gene OsNPR1 was constantly expressed at all intervals over
untreated plant.