Isolation and Characterization of Fusarium graminearum (NIFoS 14 strain) on Gastrodia elata

Gastrodia elata is an aphyllous and achlorophyllous orchid plant and has been known to need a symbiont necessary to the growth of G. elata under natural conditions. Root rot disease has a significant threat to the productivity of G. elata production. Fusarium graminearum has become one of the most studied phytopathogens in the world. Fungal samples were isolated from rot symptomatic tubers of G. elata in Anseong in May 2022. One of the fungal isolates (NIFoS 14 strain) grew fast on PDA, reaching 90 mm in 6 days at 25℃, compared with other Fusarium pathogens. Colonies were initially white with a red center, eventually covering the plate in a red mass. Microconidia were oval and fusiform, with zero or one septum ranging from 11.40 to 30.90 × 0.72 to 4.41 μm (avg. 19.06 ± 0.82 × 2.98 ± 0.11 µm, n = 30). Macroconidia were sickle-shaped from two to five septa; most had three septa, 21.44 to 42.99 × 1.80 to 4.55 μm (avg. 31.71 ± 0.91 × 3.37 ± 0.09 µm, n = 30). Based on morphological characters and multi-locus phylogenetic analysis of rDNA internal transcribed spacer (ITS), translation elongation factor 1- α (TEF1-α), and β-tubulin (TUB), the fungal isolate (NIFoS 14 strain) was identified as F. graminearum, causing root rot in many crops. With a pathogenicity test, NIFoS 14 strain showed an infection rate of 96.7%. Once F. graminearum infected, this pathogen rapidly spreads to entire tuber, thus it can cause fatal economic losses to G. elata production.