Bacillus subtilis FZB24® affects flower quantity and quality of saffron (Crocus sativus)

The effect of Bacillus subtilis FZB24® on saffron (Crocus sativus L.) was studied using saffron corms from Spain and the powdered form of B. subtilis FZB24®. Corms were soaked in water or in B. subtilis FZB24 spore solution for 15 min before sowing. Some corms were further soil drenched with the spore solution 6, 10 or 14 weeks after sowing. Growth and saffron stigma chemical composition were measured. Compared to untreated controls, application of B. subtilis FZB24 significantly increased leaf length, flowers per corm, weight of the first flower stigma, total stigma biomass; microbe addition also significantly decreased the time required for corms to sprout and the number of shoot sprouts. Compared to the controls, picrocrocin, crocetin and safranal compounds were significantly increased when the plants were soil drenched with the spore solution 14 weeks after sowing; in contrast crocin was highest in untreated controls. Results of this study suggest that application of B. subtilis FZB24® may provide some benefit to saffron growers by speeding corm growth (earlier shoot emergence) and increasing stigma biomass yield by 12%. While some treatment conditions also increased saffron chemical composition, these were generally not the same treatments that simultaneously improved growth yields and thus, more study is required.