Abstract

Drought stress has a significant challenge to crop growth, reproduction, and yield in arid regions. Microbes associated with
desert plants offer a promising solution by enhancing moisture and nutrient uptake, mitigating water stress, and ultimately
boosting crop growth and yield. In this study, the bacteria isolated from the rhizosphere of native plant Aerva javanica, found
in the Cholistan desert, were assessed for their effectiveness to promote chickpea seedlings growth. A total of 21 droughttolerant
rhizobacterial strains were isolated and characterized, with a focus on their ability to produce exopolysaccharide (EPS)
and 1-aminocyclopropane-1-carboxylic acid-deaminase (ACC-deaminase) under water-deficit conditions. These conditions
were simulated using polyethylene glycol (PEG) 6000 in the growth medium. Notably, strains CD23 and CD21 exhibited the
highest EPS production ability, yielding 10.9 and 10.4 mg L-1 of EPS, respectively, under PEG-induced drought stress however,
a minute reduction in EPS production was observed under normal conditions. Similarly, ACC-deaminase activity was
significant, measuring 3.2 and 3.2 μM mg-1 protein for strains CD23 and CD21, respectively. Further assessments were
conducted to evaluate the drought tolerance of these strains at various PEG-6000 levels in jar trials. The strains CD23 and
CD21 demonstrated promising results in enhancing chickpea growth. Subsequently, through partial gene sequencing of the
16S rRNA, these strains were identified as Acinetobacter sp. strain CD21 (accession number: MW829536) and Klebsiella sp.
strain CD23 (accession number MW829537). The production of ACC-deaminase and EPS by these desert rhizobacteria may
serve as crucial indicator for the development of inoculants that can promote chickpea growth under water-deficit conditions