Biochemical Characterization and Molecular Identification of Pseudomonas Antagonists Inhibiting Fusarium oxysporum f. sp. ciceri and Sclerotium rolfsii Sacc.

Abstract

Phytopathogens Fusarium oxysporum f. sp. ciceri and Sclerotium rolfsii sacc. are most harmful to cause Fusarium wilt in chick pea and stem rot in groundnut, respectively. The present study demonstrated identification and characterization of Pseudomonas antagonists and their in vitro antagonism against phytopathogen systems (F. oxysporum f. sp. ciceri and S. rolfsii). Total 35 Pseudomonas antagonists were derived from infested and non-infested 28 plant rhizospheres. Pseudomonas species were subjected to macro-morphological characterization and found with differences in colony shape, size, color, margin, opacity, texture, elevation and pigmentation. The Pseudomonas isolates identified as P. putida, P.aeruginosa, P. luteola, P. monteilii, P. veronii, P. fluorescens, P. pseudoalkaligenes, P. alkaligens, P. oryzihabitans, P. mendocina and P. stutzeri based on biochemical tests. The growth of test pathogens F. oxysporum and S. rolfsii were inhibited variably by Pseudomonas antagonists during in vitro antagonism. The best antagonist P. aeruginosa strain PseuJND-RSBr-11C efficiently inhibited in vitro growth of F. oxysporum (72.53%) and S. rolfsii (78.57%). Pseudomonas strains were able to produce siderophore as an iron chelating compound for test pathogen and the maximum zone was found with best antagonist strain Pseu-JND-RSBr-11C. The partial 16s rRNA gene sequencing of best antagonist strain Pseu-JNDRSBr-11C was carried out and unpaired group method with arithmetic mean (UPGMA) phylogenetic tree constructed for their similarity with other species. The best antagonist strain Pseu-JND-RSBr-11C identified as P. aeruginosa based on biochemical tests and also confirmed by 16s rRNA gene sequence.