Abstract
Thirty-two bacterial isolates were obtained from root nodules of Lupinus angustifolius growing in Northern Tunisia. Phylogenetic analyses based on recA and gyrB partial gene sequences grouped the strains into six clusters: four clusters belonged to the genus Bradyrhizobium (22 isolates), one to Microvirga (8 isolates) and one to Devosia (2 isolates), a genus that has not been previously reported to nodulate lupin. Representative strains of each group were further characterized. Multi-Locus Sequence Analysis (MLSA) based on recA and glnII gene sequences separated the strains within the genus Bradyrhizobium into four divergent clusters related to B. canariense, B. liaoningense, B. lupini, and B. algeriense, respectively. The latter might constitute a new Bradyrhizobium species. The strains in the Microvirga cluster showed high identity with M. tunisiensis. The Devosia isolates might also represent a new species within this genus. An additional phylogenetic analysis based on the symbiotic gene nodC affiliated the strains to symbiovars genistearum, mediterranense, and to a possibly new symbiovar. These results altogether contributed to the existing knowledge on the genetic diversity of lupin-nodulating microsymbionts and revealed a likely new, fast-growing, salt-tolerant rhizobial species within the genus Devosia as a potentially useful inoculant in agricultural practices or landscape restoration.
Highlights
The Leguminosae or Fabaceae family includes more than 19,700 species, many of which are agronomically important [1]
Effective nodules were collected from L. angustifolius roots growing wild or in soil collected from six different locations in Northern Tunisia: Mraissa, Takelsa, Borj Hfaied, Hammamet, Sejnane and Tabarka
Nodules were surface-sterilized with 95% ethanol for 1 min, 25% sodium hypochlorite for 3 min, rinsed several with sterile distilled water; they were individually crushed on sterile plates, and a loopful of nodule material was streaked onto yeast-mannitol agar (YMA) [36]
Summary
The Leguminosae or Fabaceae family includes more than 19,700 species, many of which are agronomically important [1]. The Genisteae tribe is presently considered to include. Lupinus is considered the largest Genisteae genus in terms of species number with around 270 species [3,4]. This genus may be divided into two groups, the first of which is centered in the Mediterranean Basin and the Canary Islands [5,6]. Comprises 13 Old World species with smooth and rough seeds [3,7]. The second group includes the New World species [8]. The New World species number ranges from 200 to 400 located in the Americas. L. angustifolius, commonly named narrow leaf lupin and blue lupin, grows wild in agricultural lands as well as in the wetlands of coastal plains in the Northern region of Tunisia
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