Novel Phl-producing genotypes of finger millet rhizosphere associated pseudomonads and assessment of their functional and genetic diversity

Abstract

Genetic diversity of phlD gene, an essential gene in the biosynthesis of 2,4-diacetylphloroglucinol, was studied by restriction fragment length polymorphism (RFLP) in 20 Phl-producing pseudomonads isolated from finger millet rhizosphere. RFLP analysis of phlD gene displayed three patterns with HaeIII and TaqI enzymes. phlD gene sequence closely correlated with RFLP results and revealed the existence of three new genotypes G, H and I. Further, the phylogenetic and concatenated sequence analysis of the 16S rRNA, rpoB, gyrB, rpoD genes supported the hypothesis that these genotypes G, H and I were different from reported genotypes A-F. In all phylogenetic studies, the genotype G formed a distant clade from the groups of Pseudomonas putida and P. aeruginosa (sensu strictu), but the groups H and I were closely related to P. aeruginosa/P. stutzeri group. The Phl-producing pseudomonads exhibited antagonistic activity against Pyricularia grisea (TN508), Gaeumannomyces graminis (DSM1463), Fusarium oxysporum (DSM62297), Xanthomonas campestris (DSM3586) and Erwinia persicina (HMGU155). In addition, these strains exhibited various plant growth-promoting traits. In conclusion, this study displays the existence of novel Phl-producing pseudomonads genotypes G, H and I from finger millet rhizosphere, which formed taxonomically outward phylogenetic lineage from the groups of P. putida and P. aeruginosa (sensu strictu).

Keywords: 2,4-DAPG; HCN; IAA; PGPR; Pseudomonas; biocontrol.