Abstract:

To determine the pathogenic species and biological characteristics of root rot in white clover （Trifolium repens） in Xinjiang， root fungi were isolated from symptomatic white clover roots collected from 11 counties （cities） in Xinjiang. The isolated fungi were identified through morphology and multi-gene sequences including ITS， EF1-α， and RPB2. Among the isolates obtained， Fusarium avenaceum accounted for 51.69%， Fusarium oxysporum 17.42%， Fusarium redolens 4.50%， and Fusarium equiseti 26.40%. Pathogenicity assays revealed all four Fusarium species to be pathogenic to white clover roots， with the following ranking of pathogenicity： F. oxysporum>F. redolens>F. equiseti>F. avenaceum. Biological characteristic results showed F. avenaceum grew well at 15-25 ℃， while the optimal mycelial growth temperature for the other three Fusarium species was 25 ℃. All four Fusarium species exhibited optimal mycelial growth at pH 7-9， with no significant differences observed under different light conditions. F. oxysporum and F. avenaceum showed optimal mycelial growth on potato dextrose agar and inulin， while F. redolens and F. equiseti grew better on Czapek's medium， with better utilization of polyol carbon sources. The optimal nitrogen source for F. avenaceum and F. equiseti was peptone， while the other two pathogens grew better on beef extract. Sporulation was best at 25-30 ℃ and pH 6-8 for all four Fusarium species. Under different light conditions， except for F. oxysporum and F. redolens showing significantly increased sporulation under 12-hour light-dark alternation， no significant differences were observed in sporulation among the species. Optimal sporulation media were potato saccharose agar for F. oxysporum and F. redolens， and oatmeal aga and corn meal agar for F. avenaceum and F. equiseti， respectively. Optimal carbon sources for sporulation were sorbitol， glucose， maltose， and soluble starch for F. avenaceum， F. oxysporum， F. redolens， and F. equiseti， respectively. The optimal nitrogen source for the former two pathogens was potassium nitrate， while for the latter two， it was yeast extract. The lethal temperature for F. oxysporum and F. redolens was 64 ℃ for 10 minutes， while for F. avenaceum and F. equiseti， it was 55 ℃ for 10 minutes. Except for F. oxysporum， the other three pathogens represent first-time occurrences on white clover and are considered newly recorded pathogens of that plant species.

Key words: Trifolium repens, Fusarium root rot, identification, biological characteristics