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Subject: Plant Pathology × Author: Giri, Madhu S. × Start date: 2013 × Type: Thesis × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    Studies on Induced Resistance in Pomegranate Against Bacterial Blight Pathogen Xanthomonas axonopodis pv. Punicae
    (University of Agricultural Science, Dharwad, 2015-07) Giri, Madhu S.; Benagi, V. I.
    Bacterial blight of pomegranate caused by Xanthomonas axonopodis pv. punicae (Hingorani and Singh) Vauterin et al. (Xap) is a major disease, which cause heavy losses to pomegranate farmers. Considering the magnitude of this disease, investigations were undertaken to study the pathogen and disease thoroughly in bringing out appropriate management aspects to mitigate the problem effectively. Survey carried out during 2011-12 in all bahars revealed that the highest disease incidence and severity on fruit was recorded in Bellary district and no disease in the orchards of Sangli district of Maharashtra. The growth of bacterium on 12 solid media showed considerable differences with respect to colony colour, appearance and fuscan pigment production. The bacterium was positive for KOH solubility, catalase test, gelatin liquefaction, starch hydrolysis, asculin hydrolysis, acid production from glucose, H2S production from cysteine hydrochloride and negative for Gram’s reaction, gas production from glucose, urease production, citrate utilization and indole production. PCR amplification of gyrB gene confirmed the identity of the pathogen as Xap. The chloroform extract of Adathoda vasica, ethyl acetate extract of Allium sativum and Salvadora persica successfully inhibited the Xap while all the four solvent extracts (acetone, ethyl acetate, chloroform and methanol) of soapnut failed to show inhibition. GCMS analysis of effective TLC fractions indicated the presence of 17, 30 and 51 different bio-active compounds in A. vasica. A. sativum and S. persica extracts respectively. The dual culture assay against pathogen revealed that, nine strains were found highly potent antagonist against Xap and produced siderphore, HCN, fluorescein, pyocyanin and antimicrobial metabolites. Among the elicitors bactikill, Pseudomonas fluorescens and Bacillus subtilis inhibited Xap. Among five chemical elicitors, four showed phytotoxicity at different concentration on young seedlings of pomegranate. β-amino butyric acid showed maximum peroxidase activity. Maximum poly phenol oxidase activity was observed in pomegranate plants treated with P. fluorescens and bromopal.