First record of Hyphopichia burtonii isolated from the storage pest Sitophilus zeamais and its bioactivity against mycotoxigenic fungi

Abstract

Corn weevil (Sitophilus zeamais) is one of the most destructive pests of corn seeds during storage. The weevil may be a vector of mycotoxigenic fungi or yeast contaminating seed lots. In this study, an unknown yeast species was isolated from corn weevils found in stored corn seeds. We hypothesized that this yeast had an antifungal activity thereby inhibiting growth of mycotoxigenic fungi in corn seeds. The yeast species was identified as Hyphopichia burtonii, using combined morphological and molecular assays, and its potential inhibitory activity was assessed in vitro (spread plate and dual culture) against three known mycotoxigenic fungi, Fusarium verticillioides, Aspergillus niger and A. fl avus. Screening of the antagonistic activity of the yeast isolate showed 50 – 69% colony growth inhibition of three fungi when the yeast was spread plated on PDA but only slight inhibition (5.8 – 13.7% growth inhibition) in the dual culture assay. The sporulation of the fungi was also affected at 57 – 96% and 29 – 40% in spread plating and dual culture assay, respectively. In addition, volatile and non-volatile fractions also showed a reduction in mycelial growth. Variable responses were observed among the mycotoxigenic fungi. Further research would be interesting on the potential utilization of the antagonistic yeast to reduce fungal growth and sporulation, and possible mitigation of mycotoxin contamination in corn grains. To our knowledge, this is the first record of H. burtonii isolated from an insect, specifically S. zeamais.