Increased detection of Fusarium spp. and Bipolaris sorokiniana in seed by the addition of paraquat in the culture medium
Seed germination complicates seed health tests performed on agar culture media. The objective of this research was to identify an inhibitor of seed germination that does not affect recovery of Fusarium spp. and Bipolaris sorokiniana, two fungal pathogens that reduce seed germination and seed health. During preliminary assays, NaCl was rejected while paraquat was identified as the best candidate. Paraquat doses ranging from 0 to 80 mg L-1 were evaluated for the recovery of Fusarium spp. on peptone-PCNB (pentachloronitrobenzene) agar and for the recovery of B. sorokiniana on a PDA-benomyl medium. Seed lots of oat, wheat, and barley, infected at different degrees, were used for the trials. Contamination with both fungi as well as total and detrimental germinations were determined after 7 d. Doses of 40 mg L-1 for Fusarium spp. and 50 mg L-1 for B. sorokiniana detection were identified as the most efficient. We also noticed a reduction in some contaminants such as yeasts and Rhizopus spp. The addition of paraquat into culture media to detect these pathogens constitutes a significant improvement of the seed health testing techniques used in cereals.