Pseudomonas sp. and Serratia odorifera: saline soil rhizoplane bacteria identified from Mamaghan (East Azarbaijan, Iran) that improve wheat seed germination under salinity stress.

Abstract

Salinity disrupts the germination and growth of seedlings in plants and reduces the population of soil microorganisms, especially bacteria. Scientists have found that each normal soil contains 600 million bacteria, consisting of 20,000 species, and their number is reduced to 1 million bacteria, consisting of 5000 to 8000 species, under salt stress. Many engineering methods are not practical. One of the biological methods is seed inoculation with plant growth-promoting rhizobacteria (PGPR). PGPR improves the morphological traits of plants, which include 1 - extracellular plant growth-promoting rhizobacteria)ePGPR( and 2 - intracellular plant growth-promoting rhizobacteria)iPGPR(. ePGPRs are present in the rhizosphere, on the rhizosphere, or in the spaces between the cells of the root cortex, while iPGPRs are present inside the specialized nodular structures of the root cells. The aim of this experiment was to investigate the effect of several rhizobacterial isolates obtained from the rhizoplane of saline soil in Momghan on seed germination and wheat seedling growth at different salinity concentrations. The experiment was conducted using a randomized complete block design. The first factor had five levels: control, 3, 6, 12, and 18 ds/m, while the second factor, involved seed inoculation with 10 bacterial isolates. The experiments were carried out in 3 replications. Isolates R₂ and R₇ promoted the growth index. At salinity levels of 3 and 6 ds/m, a significant difference was observed at the 5% level. At concentrations of 12 and 18 ds/m, morphological traits improved growth. The isolates were identified using biochemical and molecular 16s rRNA tests. Isolate R₂ was placed in the genus Pseudomonas sp. and isolate R₇ in the species Serratia odorifera.