Genetic variability and fumonisin-production by Fusarium proliferatum isolated from durum wheat in Argentina

PALACIOS S. A.; SUSCA A.; STEA G.; HAIDUKOWSKI M. ; RAMIREZ M.L. ; CHULZE, S.N; FARNOCHI M. C.; MORETTI A.; TORRES A.M.

Roterdam

Conferencia; 7th Conference of The World Mycotoxin Forum y XIII the IUPAC International Symposium on Mycotoxins and Phycotoxins; 2012

AOAC

Fusarium proliferatum is one of the main pathogens associated to maize ear rot worldwide and can produce fumonisins that contaminate this cereal.  However, this fungus has a wide range of host plants besides maize, such as wheat or barley among others. Recently, studies in our laboratory have detected natural fumonisins contamination in durum wheat kernels and have isolated mainly F. proliferatum from them. The objectives of this study were to analyze - the genetic variability throught a phylogenetic analysis and - the fumonisin-producing ability of F. proliferatum strains isolated from durum wheat in Argentina. The phylogenetic study was performed based on partial sequence of EF-1a and CL genes. The Fusarium species evaluated in this study (n= 62) were identified using morphological markers and were from diverse geographic origin, hosts (wheat and maize) and year of isolation. By molecular markers, strains of F. verticillioides (6) and F. proliferatum (51) were identified. To determine their fumonisin ability, the isolates were grown on autoclaved wheat grains. After 3 weeks of incubation in the dark at 25°C, grains were dried and ground. Non-inoculated wheat grains were used as controls. Quantitation of fumonisins (FB1, FB2 and FB3) was done by HPLC with o-phthalaldehyde precolumn derivatization. The phylogenetic study performed revealed the presence of two main clusters, one grouped all the F. proliferatum strains while the other contained 7 F. verticillioides strains. Moreover, F. proliferatum isolates were separated in groups showing a high intraspecific variability, however it was not observed a correlation to geographic origin, host or year of harvest. Out of 51 F. proliferatum strains evaluated for fumonisin production in durum wheat grains, 49 showed fumonisins production in levels ranging from 1.1 to 2072.4 ìg/g. Seven strains produced more FB2 than FB1 and 11 strains produced more FB3 than FB2. Six F. verticillioides strains produced fumonisins in levels ranging from 30.1 to 301.1 µg/g. Three of these strains produced more FB3 than FB1. These results indicate that, among the fumonisin producing species, durum wheat grains are contaminated mainly by F. proliferatum, however F. verticillioides could be also found it in this cereal, presenting a high risk for human and animal health.