Isolation of Rhizobacteria from Crocus Sativus L . Rhizosphere and Their Effects on Host-Growth Promotion

Corms serve as the primary mode of reproduction for saffron, which growth state determines the yield and quality of saffron under field cultivation conditions. In this study, fourteen rhizobacteria were isolated from the rhizosphere soil of C. sativus . The findings of this study indicate that all of the rhizobacterial isolates have the capacity to synthesize indole-3-acetic acid and gibberellic acid. Among the 14 rhizobacterial isolates, four isolates exhibited the capability to solubilize phosphate, six isolates showed nitrogen fixation ability, and four isolates were identified as effective producers of siderophore. Only one isolate exhibited the capability to degrade 1-aminocyclopropane-1-carboxylate. As indicated by the findings from the field trials, it was observed that SR144 ( Paenibacillus silvae ), SR163 ( Bacillus idriensis ), SR269 ( Pseudomonas sp.), SR307 ( Stenotrophomonas sp.), and SR383 ( Stenotrophomonas maltophilia ) had a positive impact on the fresh weight of corms and leaf length of C. sativus . Additionally, a reduction in the malondialdehyde content was observed, accompanied by an elevation in the antioxidant enzyme system in corms. Further research indicates that SR307 and SR383 cause an increase in the total bacterial count, resulting in elevated levels of microbial biomass carbon and nitrogen in rhizosphere soil, and the levels of soil sucrase, urease, dehydrogenase, catalase, and alkaline phosphatase activities were also increased. Only SR383 exhibits an increase in acid phosphatase activity. Finally, the correlation analysis showed that the positive effects caused by beneficial rhizobacteria were important for the increase of corms production.