First Report of Fusarium equiseti Causing Seedling Death on Sugar Beet in Minnesota, U.S.A.

Abstract

In May 2019, sugar beet (Beta vulgaris L.) seedlings with symptoms of wilting and root tip discoloration and necrosis were found in Moorhead (46.5507° N, 96.4208° W), Minnesota, USA. Roots of infected seedlings were surface sterilized with 10% bleach for 15 seconds, rinsed with sterile distilled water and cultured on water agar (MA Mooragar®, Inc, CA) for 3 days at 23 ± 2°C. Isolates were transferred to carnation leaf agar (CLA) and incubated at room temperature (22°C) under fluorescent light for 14 days. Abundant macroconidia were produced in sporodochia. Macroconidia were 5- to 7-septate, slightly curved at the apex, and ranged from 35 to 110 ×1.2 to 3.8 μm. No microconidia were produced. Chlamydospores with thick, roughened walls were observed in chains or in clumps, and were ellipsoidal or subglobose. Single spore was transferred from CLA to potato dextrose agar (HIMEDIA Laboratories, India) produced abundant white mycelium and was pale brown where the colony was in contact with the media. The morphological features of the isolates were consistent with Fusarium equiseti (Corda) Sacc. (Leslie and Summerell 2006, Li et al. 2015). Genomic DNAs (NORGEN BIOTEK CORP, Fungi DNA Isolation Kit #26200) of two representative isolates were used for polymerase chain reaction (PCR). The second largest subunit of RNA polymerase (RPB2) was amplified by PCR with primers 5f2/7cr (O’Donnell et al. 2010). The amplified PCR product was sequenced and deposited in GenBank (accession number MW048778). A BLAST search in Genbank and the Fusarium MLST database showed 100% sequence alignment to F. equiseti with accession MK077037.1 and NRRL 25795, respectively. Pathogenicity testing was done using three sugar beet seedlings (Hilleshög proprietary material, Hilleshög Seed, LLC, Halsey, OR 97348) at cotyledonary stage grown in a pot (4˝×4˝×6˝) with six replicates. Seedlings were inoculated with F. equiseti conidial suspension (104 conidia ml-1 for 8 minutes) by the root dip method (Hanson, 2006). Mock inoculated plants were dipped in sterile water. Inoculated and control plants were placed in the greenhouse at 25 ± 2°C, and 75 to 85% relative humidity. One week later, inoculated seedlings showed root tip tissue discoloration similar to those observed in the field and non-inoculated seedlings were symptomless. This study was repeated. The fungus was re-isolated from diseased roots and confirmed to be F. equiseti based on morphological characters. Fusarium equiseti was reported on freshly harvested and stored beet in Europe but was not found to be pathogenic (Christ et al. 2011). Strausbaugh and Gillen (2009) reported the association of F. equiseti and root rot of sugar beet but did not report pathogenicity. This pathogen is reported in several crops including edible beans that is grown in rotation with sugar beet in several production areas (Jacobs et al. 2018). The most important Fusarium species reported to cause significant economic damage to sugar beet include F. oxysporum and F. secorum (Secor et al. 2014, Webb et. al. 2012). The presence of another pathogenic Fusarium species in sugar beet will require monitoring to determine how widespread it is and whether current commercial cultivars are resistant. To our knowledge, this is the first report of F. equiseti causing disease on sugar beet seedlings in Minnesota, USA.

Dispensable genome and segmental duplications drive the genome plasticity inFusarium solani

“…Isolation, DNA Extraction, and Draft Genome Sequencing Procedures for isolation, DNA extraction, library preparation, and draft genome sequencing are available in Navasca et al, 2023. In brief, we isolated Fusarium solani from galled sugarbeet by excising and sterilizing small tissues with 0.5% v/v sodium hypochlorite for 10 minutes and washing with sterile distilled water. We extracted high-molecular-weight DNA from the mycelia of pure culture F. solani sugarbeet isolate strain SB1 grown in PDB for five days following the instructions of Liu et al (2021). Agilent TapeStation and Qubit 4.0 determined the DNA quality and quantity, respectively.…”

“…Recently, we reported F. solani as an opportunistic pathogen of sugarbeet (Navasca et al, 2023). This isolate, F. solani strain SB1, was recovered from dark galls of sugarbeets, with symptoms that differ from other Fusarium diseases in sugarbeets (Hanson, 2006; Rivera et al, 2008; Secor et al, 2014; Khan et al, 2021). Electron microscopy and sequencing work confirmed that the galls contain sugarbeet material.…”

Fungal signatures of oral disease reflect environmental degradation in a facultative avian scavenger

“…We identified distinct fungal signatures within the oral cavity of nestling black kites that were associated with oral disease or different environmental pressures. In particular, the oral disease-associated fungal signature (subcluster B) encompassed opportunistic pathogens of plants and, more rarely, of vertebrates (including humans), such as F. incarnatum-equiseti species complex (Khan et al, 2021), Penicillium brevicompactum (Caro-Vadillo et al, 2007), Alternaria sp. (Williams et al, 2008), Mucor irregularis (Tang et al, 2021), M. hiemalis (Desai et al, 2013) and R. oryzae (Doub et al, 2020).…”

<i>Fusarium equiseti</i> as one of the main <i>Fusarium</i><i></i> species causing wilt and root rot of chickpeas in Morocco

“…It was recently isolated from the seeds of the fragrant wallflower (Matthiola longipetala) showing rot (Ivanović et al, 2020). Khan et al (2021) noted that F. equiseti was responsible for seedling death in sugar beet.…”