Verticillium klebahnii

General information about Verticillium klebahnii is provided below. Included are a morphological description, comments about morphologically similar species and phylogenetic affiliation. The data is from Inderbitzin et al. (2011) where additional information can be found. Host range data is from Inderbitzin and Subbarao (2014).

Species Description

Colonies on PDA after two weeks 4–6.5 cm diam, white at first, later yellow, reverse orange to yellow, then darkening due to the formation of brown-pigmented hyphae, chlamydospores and microsclerotia (Figures 8a, 8b). Aerial mycelium generally abundant, floccose, hyphae smooth-walled, 1–3.5 µm wide. Conidiophores erect or slanted (Figure 8c), generally determinate, branched or unbranched, formed disjointedly throughout the colonies, hyaline, verruculose surface ornamentation present at times, 130–700 µm in length, 3–5 µm wide, narrowing towards the apex to 2–3 µm, transversely septate, septa spaced more narrowly towards the apex. Conidiogenous cells are phialides, arranged in (1–) 2–7 (–8) whorls along conidiophores (Figure 8c). Whorls spaced 30–65 µm apart, closer towards the apex, consisting of (1–) 2–5 (–7) phialides (Figure 8c), arising below transverse septum. Apical whorls consisting of one apical and one to several lateral phialides (Figure 8c). Phialides subulate, tapering from 1.5–2.5 µm at the base to 1–1.5 µm at the tip, terminal phialides 30–60 µm long, lateral phialides 18–45 µm long (Figure 8c). Conidia hyaline, smooth-walled, cylindrical with rounded apices to oval (Figure 8d), tapering at times, (3.5–) 5.0 µm±0.5 µm (–10.0)×(1.5–) 2.5 µm±0.5 µm (–4.5) (l/w = (1.0–) 1.9±0.2 (–2.4), n = 73), accumulating at the tip of the phialides (Figure 8c). Resting mycelium, chlamydospores and microsclerotia present. Resting mycelium consisting of brown-pigmented hyphae, up to 8 µm wide (Figure 8e), chlamydospores solitary or in chains, up to 13 µm wide (Figure 8f), microsclerotia rounded or variously shaped, up to 80 µm diam and consisting of rounded to elongate cells, up to 9 µm wide (Figure 8g). Yellow-pigmented hyphal cells present, up to 7.5 µm wide, containing globules of yellow pigment, at times pigment accumulating as crystals outside the cell, up to 14 µm diam (Figure 8h).

Morphologically similar species

Verticillium klebahnii is morphologically indistinguishable from V. isaacii and V. tricorpus.

Figure 8. Morphological features of Verticillium klebahnii.

8a. Colony of strain PD659 after 10 days on PDA, frontal view. 8b. Colony of strain PD659 after 10 days on PDA, reverse view. 8c. Conidiophore of strain PD659 after 24 days on WA-p. 8d. Conidia of strain PD401 after 35 days on WA-p. 8e. Resting mycelium of strain PD657 after 32 days on WA-p. 8f. Chlamydospores of strain PD657 after 32 days on WA-p. 8g. Microsclerotia of strain PD401 after 32 days on WA-p. 8h. Hyphal cells of strain PD401 with yellow pigment and yellow crystals after 20 days on PDA. Scale bar: 8a, 8b = 2 cm; 8c = 50 µm; 8d–8h = 20 µm. Imaging method: 8a, 8b = DS; 8c, 8e–8h = BF; 8d = DIC.

Phylogenetic position

Verticillium klebahnii belongs to the group of Verticillium that produces yellow-pigmented hyphae (group Flavexudans). For a phylogenetic tree, see Figure 1 in Inderbitzin et al. (2011).

Host range and geographic distribution

These are inferred from GenBank ITS records, and most likely underestimate the current host range and geographic distribution of V. klebahnii.

SubstratesGeographic distribution# plant hosts / # countries
Artichoke (Cynara scolymus), Lettuce (Lactuca sativa) USA (CA, WA)2 / 1