Evaluation of effect of seed-borne fungi on germination, health and quality of native Fennel seed populations

Seed-borne fungi can reduce reduce the quality and quantity of crop by affecting seed health.  The aim of this study were to evaluate the germination and vigor indices of native fennel seed populations, isolate and identify the seed-borne fungi and then pathogenicity, aggressiveness, and activity of cell wall degrading enzymes (CWDEs) produced by these isolates were investigated. In order to identify of seed-borne fungi of fennel seed populations from some fields in provinces of Golestan, Zanjan, Kurdistan and Hamedan were sampled according to the International Rules for Seed Testing (ISTA). After isolation and purification, fungal isolates were identified based on morphological and molecular characteristics. Then the enzyme activity of cellulase, xylanase, pectinase and lipase as the main virulence factors secreted by isolates were evaluated. Also, pathogenicity potential and the aggressiveness of isolates were evaluated by pathogenicity test on seedlings. A total of 33 isolates were identified based on morphological and molecular characteristics that belonging to species, Alternaria alternate and Fusarium oxysporum. The results of the standard germination test showed that there was a significant difference among the native seed populations studied in the germination and vigor indices. Seed infected by seed-borne fungi significantly affects germination and vigor indices and reduces seed quality. The results showed that the lowest in the germination and vigor indices were observed by the seed population of Golestan, followed by the seed populations of Hamedan, Zanjan and Kurdistan. The results of pathogenicity test showed that about 85% of the isolates were pathogenic and weakly pathogenic and 15% were non-pathogenic isolates. Also, different levels of pathogenicity and aggressiveness were observed for various isolates of Alternaria and Fusarium species. Analyzing the activity of CWDEs produced by isolates revealed that cellulase and xylanase activities were more than important than pectinase and lipase activities for the pathogenicity of isolates and enzyme activities affects levels of pathogenicity and aggressiveness of isolates. Therefore, these findings suggested that activity levels of cellulase and xylanase are correlated with variation in pathogenicity and aggressiveness of seed-borne fungal isolates on seeding. This is the first report on identify the seed-borne fungi of Iranian native fennel seed populations, together with the investigation of the relationship among the levels of pathogenicity, aggressiveness and the activity of CWDEs produced by isolates.