Rhizosphere soil bacteria community vary and correlate with saffron quality at four locations

Saffron is the dried stigmas of Crocus sativus (Iridaceae) which is a highly prized aromatic culinary product. Soil microorganisms are a main factor affecting the production and quality of secondary metabolites and essential oils in culinary herbs, and medicinal plants. We hypothesized the microbial community between rhizosphere and quality indices of saffron (crocin, picrocrocin, and safranal) from Crocus sativus would differ between each location in the Ghayen (Iran) region, using a Metagenomic approach. Despite similar climatic conditions and agricultural practice, the quality of saffron at one location was higher than at the other locations. This can be related to different bacteria in the rhizosphere. Rhizosphere soil from four locations in Ghayen, known for its highest quality saffron, was sampled during harvesting time. From soil DNA the 16S rRNA gene sequence of each sample was obtained by RNASeq for analysis. The results indicated that rhizobacteria such as Kosakonia, Enterobacter, Salmonella, Plesiomonas, Pasteurella, Lactococcus, and Mitsuaria have a significant impact on increasing saffron quality. They are known to increase carbon source, nitrogen fixation, auxin synthesis, dissolved phosphate production, γ-aminobutyric acid (GABA) production, increase the activity of antioxidant enzymes and increase plant growth stimulants; and can improve the quality of plant secondary metabolites in saffron.