Fusarium head blight and nivalenol contamination by Fusarium cerealis in durum wheat.

DEL CANTO, A.; PALACIOS, S. A.; TORRES, A.M.

Wuhan

Conferencia; 2nd MYCOKEY International Conference Global Mycotoxin Reduction in the Food and Feed Chain; 2018

Mycokey Horizont 2020- IPP-CAAS

Abstract: Fusarium head blight (FHB) is a major fungal disease affecting wheat worldwide. It can severely reduce grain yield and quality and the infected grains could be contaminated with mycotoxins. The disease is caused mainly by species within the Fusarium graminearum species complex (FGSC). However, recently, some studies have reported the isolation of F. cerealis from scabby wheat heads. This fungus is a nivalenol producer. The objectives of this work were to evaluate the capacity of F. cerealis to cause FHB in durum wheat cultivars with different FHB resistance levels, under greenhouse conditions and to determine the nivalenol content of the infected spikes. Five durum wheat cultivars (Ciccio (S), Kofa (MR), Langdon (S), Langdon Dic3A (MR), Bonaerense INTA Carilo) were point inoculated (10 μl) at anthesis with a conidial suspension of F. cerealis (1 x 105 macroconidia/ml) previously isolated in our lab from durum wheat grains. The strain identity was confirmed comparing the partial translation elongation factor (TEF-1α, ~700 bp) gene sequence with those from GenBank Database (GenBank Accession No. KX359404). Disease severity was assessed at 21 days after inoculation. The spikes were collected at harvest time, and whole ears were finely grounded for mycotoxin extraction. Nivalenol was determined by HPLC. All wheat cultivars showed symptoms of the disease however the severity observed varied depending on the cultivar. The most affected cultivar was Ciccio with 66% of severity while the others presented less than 25%. The symptoms observed agree with those of FHB, all or portions of infected spikes prematurely whiten and in the cultivar Ciccio , which showed severe symptoms, the infected kernels were shriveled, discolored, and fungal growth was observed, besides the peduncle and portions of the rachis were also affected as they were discolored or turned dark brown. Fusarium cerealis was re-isolated from the infected heads, confirming it was the pathogen causing FHB. Regarding the mycotoxin analysis of infected spikes, nivalenol was detected in all cultivars in levels ranging from 22 to 1.3 mg/kg. There were significant differences (p≤ 0.05) in nivalenol accumulation among cultivars, being Ciccio the one with the maximum level detected. Fusarium cerealis was able to cause FHB in the durum wheat cultivars tested and to produce nivalenol in the inoculated spikes. This is the first report of F. cerealis causing FHB on durum wheat. This result should be considered when applying management strategies, because even though the incidence of F. cerealis is lower than other FGSC, the nivalenol produced contribute to the grain contamination. Especially given that nivalenol is more toxic than deoxynivalenol.