Natural occurrence of trichothecene-producing Fusaria isolated from India with particular reference to sorghum

In this study a total of 167 isolates collected from different food materials (68.8% from sorghum and the remaining from various other food materials) were assayed by PCR for amplification of the tri 5 gene present in trichothecene-producing Fusaria. Amplification of the tri 5 fragment was observed in 45 isolates (39 isolates from sorghum and 6 isolates from vegetables). Isolates found positive for presence of the tri 5 gene were classified into different morphological groups based on their cultural and conidial characters; 11 of the tri 5 positive isolates from moldy grains of sorghum, one from each morphology group were selected for further analyses. Five deoxynivalenol producers and three deoxynivalenol and Fusarenon-X producers were detected by analysing culture filtrates of the 11 isolates using GC-MS. One isolate each were identified as producers of NIV alone, or NIV along with DON or DAS toxins. Identification of these isolates to the species level was carried out using spore morphology and sequence comparison of the translation elongation factor 1-alpha (EF-1α) gene against the database as well as using phylogenetic analyses. The isolates were identified as Fusarium proliferatum (6), F. nelsonii (2), F. equiseti (1), F. thapsinum (1) and F. sacchari (1). Amplified Fragment Length Polymorphism (AFLP) based grouping clustered the isolates of same species together. This is the first detailed study of trichothecene production by Fusarium spp. associated with sorghum grain mold in India and the identification of F. nelsonii and F. thapsinum as producers of trichothecenes.