Improved growth and quality of saffron (Crocus sativus L.) in the field conditions through inoculation with selected native plant growth-promoting rhizobacteria (PGPR)

The use of bioresources such as bio-fertilizers especially those containing plant growth promoting rhizobacteria (PGPR), may be a strategy for sustainable agriculture that respects the environment while ensuring optimal plant growth. The objective of this study was to investigate the effects of selected PGPR strains on the growth, yield and quality of saffron. The bacteria tested were isolated from the saffron rhizosphere and selected for important plant beneficial activities (phosphate solubilization, siderophore, and auxin production). The best strains were identified by 16S rRNA gene sequence analysis. Strains S11P1 and S11A1a were identified as Rahnella aquatilis, while strain S12S4 belonged to the species Variovorax paradoxus. An inoculation field experiment was conducted in a 1575 m2 field area in Taliouine (Morocco). Four different inoculants were set-up: the three single selected strains and their mixture. Using the PGPR isolates as inoculum affects positively different saffron plant parameters, such as the number of leaves (28.87 ± 6.1 vs. 22.47 ± 8.19 for control treatment) and chlorophyll content. Underground parts, in particular, daughter corms production was significantly increased about 1.91 times more than the control. In addition, the quality of inoculated saffron was in accordance with the category I specifications (Crocin > 200, Picrocrocin > 70 and Safaranal >20). Overall these results bode well the possibility of using these rhizobacteria, and specially the treatment T2 (Rahnella aquatilis S11P1), as effective biofertilizers for saffron organic cultivation.