Exploring the Biodiversity of Extremophilic Yeasts from Moroccan Ecosystems: Taxonomic Diversity and Plant Growth-Promoting Potential

Morocco's diverse extreme environments, including high-altitude mountains and arid deserts, harbor a rich yet poorly explored microbial biodiversity with considerable biotechnological potential. In this study, four yeast isolates were successfully recovered from contrasting Moroccan extreme habitats and identified through Internal Transcribed Spacer (ITS) sequencing. Molecular characterization revealed the presence of three taxonomic groups, including two isolates affiliated with the genus Naganishia, one isolate identified as Rhodotorula mucilaginosa, and one isolate belonging to the genus Candida. he isolates exhibited remarkable adaptation to harsh environmental conditions, tolerating up to 2 M NaCl and 60% polyethylene glycol (PEG 6000), indicative of strong salinity and drought stress resilience. Functional screening demonstrated multiple plant growth-promoting traits, including phosphate solubilization, indole-3-acetic acid production, siderophore production, and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, while selected isolates also showed potassium-solubilizing capacity. Greenhouse evaluation using Medicago sativa demonstrated that inoculation with the most promising yeast strains significantly improved plant growth and nutrient uptake compared with non-inoculated plants. These findings underscore the remarkable biodiversity of extremophilic yeasts inhabiting Moroccan ecosystems and highlight their functional versatility. Beyond expanding current knowledge of fungal diversity in underexplored environments, this work demonstrates the potential of indigenous yeast species as valuable genetic resources for the development of sustainable microbial inoculants and climate-resilient agricultural practices.