Improvement of saffron production using <em>Curtobacterium herbarum</em> as a bioinoculant under greenhouse conditions

Plant Growth Promoting Rhizobacteria (PGPR) are natural soil bacteria which establish a beneficial relationship with their host. This microbiota community exists in the rhizosphere and inside plant tissues and stimulates plant growth by a variety of direct or indirect mechanisms. These bacterial plant promoters are frequently present in different environments, and are associated with many plant species, both wild and agricultural. Saffron is the dried stigmas of Crocus sativus (L.) and is the most expensive spice in the world. Remarkably, saffron cultivation and collection is carried out by hand and does not involve the use of machines. Additionally, 150 flowers are needed to produce one gram of dried stigmas. Hence, a slight increase in the size of the saffron filaments per plant would result in a significant increase in the production of this spice. In this study, we report the improved production of saffron using Curtobacterium herbarum Cs10, isolated from Crocus seronitus subs clusii, as a bioinoculant. The bacterial strain was selected owing to its multifunctional ability to produce siderophores, solubilize phosphate and to produce plant growth hormones like IAA. Furthermore, the isolate was tested on saffron producing plants under greenhouse conditions. The results indicate that Curtobacterium herbarum Cs10 improves the number of flowers and significantly enhances the length of the saffron filaments and overall saffron production compared to the control treated plants.