Abstract
The phylogenetic relationships among thirteen Rhizobium leguminosarum bv. viciae isolates collected from various geographical regions were studied by analysis of the 23S rRNA sequences. The average of genetic distance among the studied isolates was very narrow (ranged from 0.00 to 0.04) and the studied isolates formed two main groups based on cluster analysis. The isolates were tested for their growth on YMA medium supplemented with concentrations 10, 20 and 30% of polyethylene glycol plus control. All isolates exhibited good drought-tolerant efficiencies at 10% PEG. While most of the isolates could not tolerate up to 20% PEG, isolates of Rlv6, Rlv9, Rlv12 and Rlv13 tolerated up to 20% PEG. Keywords: Rhizobium leguminosarum , 23S rRNA gene, phylogenetic tree, diversity and drought tolerance
Highlights
Rhizobia are gram-negative bacteria that can establish a symbiotic relationship with the roots of leguminous plants and form root organ called nodule, wherein bacteria is hosted and nitrogen is fixed
The rRNA genes are very useful for investigating the phylogenetic relationships among bacteria since their evolution are slow and their gene products performs central functions in the bacterial cell (Pulawska et al, 2000). 16S rRNA gene was the most frequently used in microbial phylogeny studies (Kolbert and Persing, 1999, Ismail et al, 2013; El-Zanaty et al, 2014)
Wolde-meskel et al (2005) investigated the genetic diversity among 195 rhizobial strains isolated from root nodules of 18 agroforestry species growing in diverse zones in southern Ethiopia using polymerase chain reaction (PCR)–RFLP of the ribosomal operon (16S rRNA gene, 23S rRNA gene and the internal transcribed spacer (ITS) region between
Summary
Rhizobia are gram-negative bacteria that can establish a symbiotic relationship with the roots of leguminous plants and form root organ called nodule, wherein bacteria is hosted and nitrogen is fixed. The rRNA genes are very useful for investigating the phylogenetic relationships among bacteria since their evolution are slow and their gene products performs central functions in the bacterial cell (Pulawska et al, 2000). Previous studies showed that the 23S rRNA gene contains more genetic information and better diagnostic sequence stretches than the 16S rRNA gene. Wolde-meskel et al (2005) investigated the genetic diversity among 195 rhizobial strains isolated from root nodules of 18 agroforestry species growing in diverse zones in southern Ethiopia using PCR–RFLP of the ribosomal operon (16S rRNA gene, 23S rRNA gene and the internal transcribed spacer (ITS) region between The progress in sequencing tools and the decrease in their costs make the 23S rRNA powerful tool to elucidate the taxonomic relationships (Pulawska et al, 2000; reviewed in Hunt et al (2006) and Pei et al (2009). Wolde-meskel et al (2005) investigated the genetic diversity among 195 rhizobial strains isolated from root nodules of 18 agroforestry species growing in diverse zones in southern Ethiopia using PCR–RFLP of the ribosomal operon (16S rRNA gene, 23S rRNA gene and the internal transcribed spacer (ITS) region between
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