Effect of halotolerant rhizobacteria isolated from halophytes on the growth of sugar beet ( Beta vulgaris L.) under salt stress

<span class="paragraphSection"><div class="boxTitle">ABSTRACT</div>Utilization of rhizobacteria that have associated with plant roots in harsh environments could be a feasible strategy to deal with limits to agricultural production caused by soil salinity. Halophytes occur naturally in high-salt environments, and their roots may be associated with promising microbial candidates for promoting growth and salt tolerance in crops. This study aimed to isolate efficient halotolerant plant-growth-promoting rhizobacterial strains from halophytes and evaluate their activity and effects on sugar beet (<span style="font-style:italic;">Beta vulgaris</span> L.) growth under salinity stress. A total of 23 isolates were initially screened for their ability to secrete 1-aminocyclopropane-1-carboxylate deaminase (ACD) as well as other plant-growth-promoting characteristics and subsequently identified by sequencing the 16S rRNA gene. Three isolates, identified as <span style="font-style:italic;">Micrococcus yunnanensis</span>, <span style="font-style:italic;">Planococcus rifietoensis</span> and <span style="font-style:italic;">Variovorax paradoxus</span>, enhanced salt stress tolerance remarkably in sugar beet, resulting in greater seed germination and plant biomass, higher photosynthetic capacity and lower stress-induced ethylene production at different NaCl concentrations (50–125 mM). These results demonstrate that salinity-adapted, ACD-producing bacteria isolated from halophytes could promote sugar beet growth under saline stress conditions.</span>

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