Species diversity and geographical distribution of Fusarium species on winter wheat in two regions in Sweden

Abstract: Various Fusarium species causes some of the most common cereal diseases worldwide. Besides the yield losses that can be a result of these diseases, strains from several Fusarium species can produce mycotoxins, some very toxic. The aim of this study was to investigate which Fusarium species and how many that occurred in winter wheat grains from Mälardalen and Kalmar län, if there was any difference in the distribution of Fusarium fungi between the regions and the potential within species to produce mycotoxins belonging to the group trichothecenes. Winter wheat grains collected in 2009 from ten fields (unsprayed plots) in the two regions were analysed for Fusarium species. PCR was used to amplify the TEF region where after the samples were sequenced. The samples identified as Fusarium species were screened for the presence of the Tri5 gene necessary for trichothecene production. The results were compared with previously collected data on Fusarium spp. detected in the same ten fields using species specific primers as well as toxin analyses. In Mälardalen, Fusarium species were isolated from 234 out of 500 grains. The identified species were F. acuminatum, F. arthrosporioides, F. avenaceum, F. graminearum, F. poae and F. tricinctum. In the Kalmar area 43 of the 500 grains were infected with Fusarium species. Seven species (F. acuminatum, F. avenaceum, F. flocciferum, F. graminearum, F. langsethiae, F. poae and F. tricinctum) were identified. The differences between the amounts of infected grains in the two regions were thought to be due to humid weather conditions in Mälardalen during the time of flowering which favours Fusarium infection. In Mälardalen 132 strains of the Fusarium isolates carried the Tri5 gene and ten strains from the Kalmar area carried the gene. The majority of these strains belonged to the species F. poae. Questions arose concerning the isolates identified as F. avenaceum, F. tricinctum and F. flocciferum since some of them showed to have the Tri5 gene. These three species are not known to carry the Tri5 gene which gives reason to believe that the strains in fact belonged to other Fusarium species. It is also possible that strains from these species can carry the Tri5 gene but they have not been detected before or the gene has not been expressed. Further analyses are needed to confirm whether the Tri5 gene was present in strains from F. avenaceum, F. tricinctum and F. flocciferum. This could be made by rerunning PCR, sequencing and species identification.