Occurrence of Toxigenic Fusarium vorosii among Small Grain Cereals in Korea

Abstract

Fusarium graminearum species complex (FGSC) causes Fusarium head blight in small grain cereals. To date, four species (F. graminearum, F. asiaticum, F. boothii, and F. meridionale ) belonging to FGSC frequently occur in Korean cereals. In addition, we first reported the occurrence of additional species (F. vorosii ) within FGSC, which was isolated from barley, corn, and rice in Korea. Phylogenetic analysis of the Fusarium isolates of this group using combined multi-gene sequences confirmed species identification. Moreover, the macroconidia produced by these isolates were morphologically similar to those of the F. vorosii holotype. Chemical analysis indicated that the F. vorosii isolates produced various trichothecenes such as nivalenol and deoxynivalenol with their acetyl derivatives along with zearalenone. Pathogenicity tests demonstrated that all of the F. vorosii isolates examined were pathogenic on barley, corn, and rice with variation in aggressiveness. This study is the first report of F. vorosii in Korean cereals, their pathogenicity towards barley and corn, and their ability to produce trichothecenes and zearalenone.

Characterization of Nivalenol-Producing Fusarium asiaticum That Causes Cereal Head Blight in Korea

“…Fusarium isolates were retrieved from laboratory collections stored in 25% (v/v) glycerol at −80°C. All were single-spore isolates from barley, maize, rice, soybeans, or wheat grains collected from fields during 2014 and 2015 harvest, as previously described (Lee et al, 2016). For comparison with Korean strains, nine foreign F. asiaticum isolates were used.…”

“…For comparison with Korean strains, nine foreign F. asiaticum isolates were used. Seven of them were obtained from the Agriculture Research Service Culture Collection (ARS) and two were isolated directly from Japanese brown rice, as described previously (Lee et al, 2016). Freezedried ARS-isolates were revived on potato dextrose agar (PDA).…”

“…Species and Btype trichothecene genotypes were respectively determined based on PCR assays targeting the translation elongation factor 1-alpha (TEF-1α) and TRI12 genes, as described previously by Starkey et al (2007). Phylogenetic analyses were performed on three genes (TEF-1α, MAT1-1-3, and TRI101), as described previously by Lee et al (2016).…”

“…Mycotoxin analysis. Trichothecene and ZEA levels were prepared, harvested and measured in triplicate during fungal growth in rice medium as described previously (Lee et al, 2016) with minor modifications (6 ml water with 10 g long-grain rice). For NIV analysis, 2 g of ground rice cultures were extracted with 20 ml water at 300 rpm for 1 h, centrifuged at 3,600 rpm for 10 min, and filtered through Whatman No.…”

“…Disease assessment. Pathogenicity of fungal isolates was evaluated as previously described (Lee et al, 2016) using susceptible cultivars of wheat (cv. Keumkang), barley (cv.…”