Viability, Growth and Virulence of Harpophora maydis Isolates Preserved Under Different Storage Methods

Abstract

Two isolates of Harpophora maydis, the causal agent of maize late wilt, were evaluated for viability, morphological characters, radial growth and virulence using twenty storage methods for 3, 12 and 24 months. Colonized discs preserved in sterile distilled water at room temperature (RT) from 25 to 32°C (SDW.RT) was the best treatment since the two isolates were recovered from all samples during the storage periods, with 90, 90 and 82.5%, respectively with no negative effect on their radial growth, morphological characters and virulence compared with the original isolates. Also, storage in 30% glycerol at room temperature (G30%. RT) exhibited a good degree of survivability (from 60 to 90%) and the examined characters were not altered. Unfortunately, fungal isolates were not able to recover after three months of storage when preserved by the methods of potato dextrose yeast agar with paraffin oil at RT, G30%. 4°C, G30%. -20°C and silica gel at -20°C. Based on the statistical analysis of the obtained results, it could be concluded that SDW.RT is simple, reliable and economic preservation method for H. maydis, moreover preservation in G30%.RT could be used along with SDW.RT or as alternative method for the tested fungus.