عنوان مقاله [English]
The aim of this study was to identification of the Fusarium species associated with root and corm of saffron and evaluation of extracellular enzymes activity of secreted by them. In order to study the species of Fusarium, a total of 53 root and corm samples were randomly collected from saffron fields of South Khorasan provinces during 2017 growing season. After washing the samples with sterile water and surface disinfested with 1% sodium hypochlorite, small pieces of root and corm were cultured on general and specific culture media. Purification of fungal colonies was performed using single spore and hyphal tip methods on 2% water agar medium. Identification of fungi based on the microscopic and morphological characteristics was performed with valid identification keys. According to morphological characters, the species F. oxysporum, F. graminearum, F. culmorum and F. proliferatum were identified. The results obtained from molecular analysis using species-specific primers confirmed the morphological identification. The results revealed that 22.6% of the saffron samples were contaminated by Fusarium species. Based on morphological and molecular observations, F. oxysporum was the predominant species with the highest isolation frequency in samples of 9.4% followed by F. culmorum (5.7%), F. proliferatum (3.8%) and F. graminearum (3.8%). Results showed that all Fusarium isolates were capable of producing cell wall degrading enzymes (CWDEs), mainly cellulase and xylanase. Levels of cellulase, xylanase and pectinase enzymes activity in this study was higher than lipase activity in all isolates examined. Activity trend analysis of CWDEs showed that for most of the isolates tested the maximum levels of cellulase, xylanase, pectinase and lipase activity were observed at 72, 96, 144 and 192 h post-culturing (hpc) on liquid medium, respectively. Then, the enzymes activities decreased gradually with time, until it remained at constant levels. Based on present literatures, F. graminearum, F. culmorum and F. proliferatum are first reported from saffron in Iran.