BSc-MSc (Integrated)

The study enititled ‘evaluation of systemic acquired resistance and induced
systemic resistance on the suppression of foliar blight disease of amaranthus
(Amaranthus tricolor L.)’ was conducted at the Department of Agricultural
Microbiology and Department of Plant Biotechnology, College of Agriculture,
Vellayani.
The study was focused on the evaluation of the combined effect of mutualistic
fungus Piriformospora indica and ActigardTM 50WG whose active ingredient is
Acibenzolar-S-methyl, the plant activator which is a synthetic structural analog of
salicylic acid. In vitro studies were done for testing the antagonism of P. indica and
ASM on the growth of R. solani by making use of dual culture plate assay and poisoned
food technique respectively. The results present no direct in vitro antagonism on the
pathogen by both P. indica and ASM. Colonization of P. indica in the roots of
amaranthus were confirmed by two staining procedures, trypan blue staining and
WGA-AF 488 staining. It was further validated by PCR amplification using species
specific primers for TEF1 gene of P. indica. The results of confocal microscopy
suggest that coculture of P. indica and amaranthus in vitro can be a better strategy for
better colonization of the fungus in the roots.
Disease suppression and growth promotion studies were done using different
treatments comprising of the fungus and ASM applied individually and in
combinations of both. ASM was applied both as foliar spray and root drenching.
Colonization study after ASM treatment revealed that ASM application in the root zone
of the plants can result in reduction of percentage root colonization of the fungus, P.
indica.
The minimum disease intensity was found in chemical control followed by
plants treated with P. indica. P. indica was found effective in reducing the foliar blight
disease index in amaranthus plants by 50%, 67% and 30.34% respectively on 3rd ,4th

and 5th day of challenge inoculation when compared to control plants. In the treatments
involving ASM on the 3rd day after pathogen inoculation PDI was found to more than
the control. However, a decrease of 6.99% and 5.34% in PDI of T2 was observed on
the 4th and 5th day after inoculation with R.solani. Although ASM did not show
significant decrease in percentage disease index, the progression of the disease as days
passed after inoculation with R. solani was very low. This might be due to the resistance
imparted by ASM to the amaranthus plants. However, the combinations of P. indica
and ASM did not display any convincing results in the enhancement of growth
parameters when compared to the control as ASM was found to cause a decrease in the
plant growth while it imparts resistance to the amaranthus plants against foliar blight
caused by R. solani.
The current investigation acknowledges the growth promoting effects of P.
indica and role of P. indica and ASM in imparting resistance against the foliar blight
disease caused by Rhizoctonia solani.