Halotolerant Bacillus Species as Plant Growth Promoting Rhizobacteria from Hyper – Arid Area of Algeria

Abstract

The aim of this study was to determine the diversity of aerobic halophilic and halotolerant Bacillus (AHHB) Plant Growth Promoting Rhizobacteria (PGPR), producing hydrolytic exo-enzymes and their inoculation effect in on two cowpea plants. Therefore, soil dilution plate technique was performed on Tryptic Soy Agar complemented with a thermal pretreatment to select Bacillus strains associated to Phoenix dactylifera rhizosphere growing in hypersaline and arid soil of Algeria (In Salah, Tamanrasset). The inoculation effect of these strains on cowpea plants growth was assessed based on biometric and physiological parameters. As results, thirteen halophilic, halotolerant and non-halophilic Bacillus strains were isolated. Upon screening, all strains are capable of producing at least two hydrolytic enzymes under saline conditions and most of the strains (n=10/13) showed at least two PGP traits. Strains were identified based on their phenotypic and biochemical characteristics as members of Bacillus genera. The inoculation of these strains in cowpeas had significantly improve biometrics and physiological growth parameters of inoculated plant. Based on general plant aspect, four strains are distinguished: RP 7 (B. coagulans), RP 8 (B. circulans), RP 10 (Paenibacillus polymyxa) and RP 12 (B. circulans). The isolation and characterization of halophilic and halotolerant Bacillus strains has increased knowledge of the rhizocompetent bacterial community associated with date palm in saline and arid soils. AHHB have proven to be highly effective strains to improve cowpea plant growth and development.