Survey of Freshly Harvested Oat Grains from Southern Brazil Reveals High Incidence of Type B Trichothecenes and Associated Fusarium Species

The current study investigated the fungal diversity in freshly harvested oat samples from the two largest production regions in Brazil, Paraná (PR) and Rio Grande do Sul (RS), focusing primarily on the Fusarium genus and the presence of type B trichothecenes. The majority of the isolates belonged to the Fusarium sambucinum species complex, and were identified as F. graminearum sensu stricto (s.s.), F. meridionale, and F. poae. In the RS region, F. poae was the most frequent fungus, while F. graminearum s.s. was the most frequent in the PR region. The F. graminearum s.s. isolates were 15-ADON genotype, while F. meridionale and F. poae were NIV genotype. Mycotoxin analysis revealed that 92% and 100% of the samples from PR and RS were contaminated with type B trichothecenes, respectively. Oat grains from PR were predominantly contaminated with DON, whereas NIV was predominant in oats from RS. Twenty-four percent of the samples were contaminated with DON at levels higher than Brazilian regulations. Co-contamination of DON, its derivatives, and NIV was observed in 84% and 57.7% of the samples from PR and RS, respectively. The results provide new information on Fusarium contamination in Brazilian oats, highlighting the importance of further studies on mycotoxins.

Survey of Freshly-Harvested Oat Grains from Southern Brazil Reveals High Incidence of Type B Trichothecenes and Associated Fusarium Species

Oats are a nutrient rich cereal used for animal feed and growing in human consumption. This cereal can be affected by Fusarium spp., causing the disease Fusarium Head Blight. This disease is caused mainly by species within the Fusarium graminearum species complex, and are also responsible for producing mycotoxins that are harmful to humans and animals. This study aimed to investigate fungal diversity in Brazilian oat samples, focusing on the Fusarium sambucinum species complex and the presence of type B trichothecenes (deoxynivalenol and its derivatives, and nivalenol) from two different regions; Paraná (PR) and Rio Grande do Sul (RS). The isolated fungi from oat grains were identified as species from the genera: Fusarium, Phoma and Alternaria. The majority of Fusarium isolates belonged to the Fusarium sambucinum species complex; identified as F. graminearum s.s., F. meridionale and F. poae. In the RS region, F. poae was the most frequent fungus, while FGSC was the most frequent in the PR region. The majority of F. graminearum s.s. isolates were of the 15-ADON genotype, while some 3-ADON genotypes were identified; however, F. meridionale and F. poae were all of the NIV genotype. Mycotoxin analysis revealed that 92% and 100% of the samples from PR and RS were contaminated with type B trichothecenes, respectively. The oats from PR were predominantly contaminated with DON, whereas NIV was predominant in oats from RS. Analysis showed that 24% of the samples were contaminated with DON at levels higher than Brazilian regulations. Co-contamination of DON, its derivatives and NIV was observed in 84% and 57.7% of the samples from PR and RS, respectively. The results provide new information on Fusarium contamination in Brazilian oats, highlighting the importance for further studies on mycotoxins.

Discovery of Three Novel Cytospora Species in Thailand and Their Antagonistic Potential

During an ongoing research survey of saprobic fungi in Thailand, four coelomycetous strains were isolated from decaying leaves in Chiang Mai and Phitsanulok Provinces. Morphological characteristics demonstrated that these taxa are typical of Cytospora in forming multi-loculate, entostromatic conidiomata, branched or unbranched conidiophores, with enteroblastic, phialidic conidiogenous cells and hyaline, allantoid, aseptate conidia. Multiloci phylogeny of ITS, LSU, ACT, RPB2, TEF1-α and TUB2 confirmed these taxa are distinct new species in Cytospora in Cytosporaceae (Diaporthales, Sordariomycetes), viz., Cytospora chiangmaiensis, C. phitsanulokensis and C. shoreae. Cytospora chiangmaiensis has a close phylogenetic relationship with C. shoreae, while C. phitsanulokensis is sister to C. acaciae. These three novel species were also preliminary screened for their antagonistic activity against five plant pathogenic fungi: Colletotrichumfructicola, Co. siamense, Co. artocarpicola, Co. viniferum and Fusarium sambucinum. Cytospora shoreae and C. phitsanulokensis showed >60% inhibition against Co. viniferum and F. sambucinum, while C. chiangmaiensis had moderate inhibition activity against all pathogens.

De novo Sequencing of Novel Mycoviruses From Fusarium sambucinum: An Attempt on Direct RNA Sequencing of Viral dsRNAs

An increasing number of viruses are continuously being found in a wide range of organisms, including fungi. Recent studies have revealed a wide viral diversity in microbes and a potential importance of these viruses in the natural environment. Although virus exploration has been accelerated by short-read, high-throughput sequencing (HTS), and viral de novo sequencing is still challenging because of several biological/molecular features such as micro-diversity and secondary structure of RNA genomes. This study conducted de novo sequencing of multiple double-stranded (ds) RNA (dsRNA) elements that were obtained from fungal viruses infecting two Fusarium sambucinum strains, FA1837 and FA2242, using conventional HTS and long-read direct RNA sequencing (DRS). De novo assembly of the read data from both technologies generated near-entire genomic sequence of the viruses, and the sequence homology search and phylogenetic analysis suggested that these represented novel species of the Hypoviridae, Totiviridae, and Mitoviridae families. However, the DRS-based consensus sequences contained numerous indel errors that differed from the HTS consensus sequences, and these errors hampered accurate open reading frame (ORF) prediction. Although with its present performance, the use of DRS is premature to determine viral genome sequences, the DRS-mediated sequencing shows great potential as a user-friendly platform for a one-shot, whole-genome sequencing of RNA viruses due to its long-reading ability and relative structure-tolerant nature.