Effect of a flower-isolated yeast on seed germination and seedling growth of carrot and cauliflower

The study of growth-promoting microorganisms is vital due to their potential for developing agricultural technologies that enhance the sustainability of production systems. The identification, isolation, and production of these organisms can contribute to the generating new, high-value agricultural bioinputs. Therefore, this research aimed to evaluate the effect of treating vegetable seeds (carrot and cauliflower) with a yeast cell culture on seed quality and seedling production. The yeast strain used in the experiments (CHAP-208), isolated from Senna macranthera flowers, was identified as Rhodotorula sp. During cultivation, it produced ~ 2.8 mg/L of indole acetic acid (IAA). Subsequent germination and seedling growth experiments were conducted under laboratory conditions for both carrot and cauliflower, followed by seedling production trials in an agricultural greenhouse for cauliflower. Imbibing carrot seeds for 2 h in the Rhodotorula sp. CHAP-208 cell suspension enhenced seedling development under laboratory conditions. Soaking cauliflower seeds did not affect germination but increased plant emergence rates and root length in the greenhouse environment. This effect may be linked to the auxin-production capacity of Rhodotorula sp. CHAP-208, marking the first report of a yeast isolated from S. macranthera flowers with high plant growth-promoting activity. These findings suggest that Rhodotorula sp. CHAP-208 is a promising bioinoculant for promoting plant growth. Future studies should quantify IAA levels before and after seed soaking, as well as in samples from the resulting seedlings and plants.