Hidden Helpers: Exploring Plant Growth-Promoting Activities of Endophytes and their Functional Diversity Across Different Organs of Saffron crocus (Crocus sativus L.).

This study addresses a critical knowledge gap by evaluating endophytes from Crocus sativus for a range of plant growth-promoting (PGP) activities and assessing their functional diversity using community-weighted mean (CWM) and functional diversity (FD) indices-an area that remains largely unexplored in plant-microbe interactions. We examined 84 potential endophytes for auxin production, ammonia and urease activity, phosphate solubilization, siderophore and amylase production, and antifungal properties. Endophytes belonging to Dothideomycetes exhibited only auxin production and urease activity, while members of other groups were positive for all assessed traits. FD indices varied significantly across sites and plant organs, with roots generally showing the highest values. The CWM of functional traits also differed among organs, with roots and corms displaying the highest values for auxin, ammonia, phosphate solubilization, and antifungal activity. Bacillus species, particularly B. cereus, were notable for auxin, amylase, and antifungal activities, while Streptomyces and Trichoderma strains also showed strong antifungal effects. Significant effects of site and organ type were observed for several functional traits, highlighting ecological variability across environments and plant parts. Additionally, endophyte responses to drought, temperature, and pH stress were assessed, with B. cereus, Streptomyces lydicus, and Trichoderma harzianum demonstrating superior growth under stress conditions. These findings advance ecological understanding of plant-endophyte interactions and suggest innovative strategies to enhance saffron yield and disease resistance in response to the growing challenges faced in saffron cultivation.