This study aimed to isolate, characterize and assess the plant
growth-promoting traits of bacterial isolates inhabiting the rhizosphere of
Solanum lycopersicum L. (tomato) against three plants—Eruca sativa, Lepidium
sativum and Raphanus sativum—from Saudi Arabia's Al-Ahsa region.
Methodology: bacterial isolate designated as SLK10 was obtained
from the rhizosphere of tomato grown in the Al-Ahsa region, Saudi Arabia.
SLK10 was further characterized morphologically, biochemically and
genotypically using 16S rRNA gene sequencing. The roles in alleviating salt
stress effects on three important economic crops were also assessed by
implementing a cross-inoculation strategy.
SLK10 formed a circular, non-pigmented and raised colony with an entire
margin. The cells were rod shaped and Gram negative. SLK10 displayed multiple
plant growth-stimulating features, such as the solubilization of inorganic
phosphate and the production of phytohormones and acetoin. Comparative
sequence analysis of 16S rRNA gene revealed that SLK10 belonged to Pseudomonas
monteilii, to which it exhibited 99.86% sequence homology. SLK10
significantly promoted the length of primary root, stem and number of leaves
in Eruca sativa, Lepidium sativumand Raphanus sativus
growing under 1000 ppm salt stress. The number of leaves in L. sativum
and R. sativus growing under 2000 ppm salt stress was substantially
enhanced by SLK10.
Interpretation: SLK10 is a plant growth-promoting
bacterium and can be used as a green fertilizer to increase soil fertility
and plant productivity in the Eastern region of Saudi Arabia.
Key words: Pseudomonas species, Rhizobacteria,
Rhizosphere, Salt stress, Solanum lycopersicum