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Abstract
Chlamydospores are vital asexual resting cells, which allow most of the Fusarium pathogenic strains to retain their longevity, thus ensuring survival of viable reproductive cells. This study suggested that both abiotic – extreme temperature and growth media, and biotic – antagonistic Bacillus amyloliquefaciens SMCD 518 and mycoparasititic Acremonium strictum SMCD 504 are natural stressors able to shift chlamydospores formation in Fusarium graminearum and F. sporotrichioides under in vitro conditions. In F. sporotrichioides, Minimal Conversion Media (MCM) with mannitol supplement induced high chlamydospore size, and chain abundance at optimal 21°C and extreme 37°C temperatures, respectively. F. graminearum showed low chlamydospore formation on MCM–mannitol, even when exposed to 37°C under prolonged 5 days incubation. Generally, F. sporotrichioides has higher chlamydospore abundance, longer chlamydospore chain, and production rapidity compared to F. graminearum in both abiotic and biotic treatments. However, biocontrol bacteria and mycoparasite posed minimal effects on chlamydospore formation, as compared to abiotic stressors, thus controlling the Fusaria but not triggering them to generate chlamydospores as protection shields.
Acknowledgements
This research was financially supported by Natural Sciences and Engineering Research Council of Canada (NSERC) discovery grant. We would like to thank Bill Reid, Dinka Besic, and Sohail Qazi for statistical assistances. The authors would like to thank Dr de Freitas and Henry Chau for microscopy technical assistance and helpful discussions.
Notes
1. Biotic agents were assessed only on 21°C, because its exposition at 37°C for a prolonged incubation time – 5 days caused bacterium cells dead and mycoparasite restrained growth (data not shown).