Induced systemic resistance by 2,4-diacetylphloroglucinol positive fluorescent <em>Pseudomonas </em> strains against rice sheath blight

Abstract

Rice sheath blight arising due to lack of systemic resistance against causative agent <em>Rhizoctonia solani</em> has been a major economic threat to rice growers across the globe. This warrants induced systemic resistance (ISR) in plant to make them disease resistant. Application of antibiotic producing <em>Pseudomonads</em> that also secrete defense inducing enzymes is known to impart resistance to plants. Here, we report induction of the induced systemic resistance (ISR) by six strains of rhizosphere fluorescent <em>Pseudomonas </em> possessing 2,4-diacetyl phloroglucinol (2,4-DAPG) antibiotic genes against rice sheath blight pathogen <em>Rhizoctonia solani</em>. In the preliminary screening, isolate EP5 (endophytic <em>Pseudomonas fluorescens</em>) showed 76.5% inhibition against <em>R. solani</em>. EP5 treated rice grains showed the highest germination of 96.6%, mean root length of 15.3 cm, shoot length of 12.6 cm and vigour index of 2104.9. Paddy grains treated with EP5 (through seed treatment followed by root dipping) upon challenge inoculation with <em>R. solani</em> (Rs1) gave higher activity of peroxidase (PO) 2.50 change in absorbance at 470 nm/min/mg protein), polyphenol oxidases (PPO), 2.25 change absorbance at 420 nm/ min/mg protein, phenyl alanine ammonia lyase (PAL) and 28.5 nmol transcinnamic acid/hr/mg protein. 2,4-DAPG positive fluorescent <em>Pseudomonas </em> strains produced PO, PPO, PAL and 28.5 nmol transcinnamic that resulted in ISR against rice sheath blight pathogen <em>R. solani</em>.