|CERON-BUSTAMANTE, M - Postgraduate College|
|AYALA-ESCOBAR, V - Postgraduate College|
|NAVA-DIAZ, C - Postgraduate College|
|LEYVA-MIR, G - Autonomous University Of The State Of Mexico|
|VILLASENOR-MIR, H - Instituto Nacional De Investigaciones Forestales Y Agropecuarias (INIFAP)|
Submitted to: Plant Disease
Publication Type: Research Notes
Publication Acceptance Date: 4/7/2016
Publication Date: 8/1/2016
Citation: Ceron-Bustamante, M., Ayala-Escobar, V., Nava-Diaz, C., Ward, T.J., Leyva-Mir, G., Villasenor-Mir, H.E. 2016. First report of Fusarium meridionale causing Fusarium Head Blight of wheat in Mexico. Plant Disease. 100(8):1790.
Technical Abstract: Fusarium head blight (FHB), also known as scab, is a destructive disease of small grain cereals caused by several species belonging to the Fusarium graminearum species complex (FGSC). Members of the FGSC produce trichothecene toxins that represent a threat to human and animal health (1). Despite the global significance of FHB and trichothecene contaminated grain, little is known about the identity of FHB pathogens present in Mexico. During the growing seasons of 2013 and 2014, three wheat heads with symptoms of Fusarium Head Blight were collected from each of 40 localities in Tlaxcala, Puebla and Mexico states. Symptomatic seeds were surface-sterilized for 3 min in 3% sodium hypochlorite and rinsed three times with autoclaved distilled water. Fungi were isolated using the freezing blotter test (2). Isolated colonies that resembled Fusarium species were transferred to water-agar and sub-cultured on potato dextrose agar (PDA) plates using a single spore technique. Pathogenicity tests were performed in a greenhouse by using single-floret point inoculation of 45 day-old wheat with a 10 µL suspension of 105 macroconidia/ml. Inoculated heads were covered with a plastic bag for three days to insure infection, and fungi were re-isolated from wheat heads showing typical FHB symptoms after 6 days. Multilocus genotyping (MLGT), which uses a set of 52 species or trichothecene genotype-specific probes in a multiplexed allele specific primer extension (ASPE) assay (3), was used to determine the species identity and trichothecene type for each of the fungi recovered from the pathogenicity test. Three isolates were identified as F. meridionale with the nivalenol (NIV) trichothecene genotype. These isolates have been deposited in the ARS Culture Collection, Peoria, IL under NRRL accession numbers F644, F585 and F572. Species identifications were validated through BLAST analyses of EF1-a sequences from these isolates against the set of curated sequences available in FUSARIUM-ID (4). All EF1-a sequences showed 99.84% identity (643 of 644 bases identical) with sequences of F. meridionale in the database. The next closest matches had 638 of 644 (99.06%) bases identical. The isolates on PDA produced abundant brown aerial mycelium and formed red-brown pigments in media. On SNA media, macroconidia were abundant, falcate with the dorsal side more curved than the ventral, with four septae, 27-46 x 3-4 µm. Microconidia were not observed. FHB pathogens with the NIV toxin type are relatively rare in North America, with deoxynivalenol (DON) being far more common, however NIV is reported to be more toxic to humans and animals (5). To the best of our knowledge, this is the first report of F. meridionale in Mexico, or in any production field in North America. Although the isolates described here were obtained from wheat, F. meridionale have been frequently reported in association with maize and Fusarium ear rot, which is of great concern in Mexico because this cereal constitutes the major staple food in this country.