Fusarium fredkrugeri Sandoval-Denis, Crous & W.J. Swart

Sandoval-Denis, Marcelo, Swart, Wijnand J. & Crous, Pedro W., 2018, New Fusarium species from the Kruger National Park, South Africa, MycoKeys 34, pp. 63-92 : 63

Fusarium fredkrugeri Sandoval-Denis, Crous & W.J. Swart sp. nov. Fig. 6

Diagnosis.

Differs from Fusarium dlaminii Marasas, P.E. Nelson & Toussoun by producing only one type of aerial conidia, shorter sporodochial conidia and the absence of chlamydospores.

Type.

South Africa, Kruger National Park, Skukuza, Granite Supersite, 25°06'48.6"S, 31°34'36.5"E, from rhizosphere soil of Melhania acuminata , 23 Mar 2015, W.J. Swart, holotype CBS H-23496, dried culture on OA, culture ex-holotype CBS 144209 = CPC 33747.

Description.

Colonies on PDA growing in the dark with an average radial growth rate of 4.7-5.8 mm/d and reaching 22-35 mm diam. in 7 d at 24 °C, filling an entire 9 cm Petri dish in 7 d at 27 and 30 °C. Minimum temperature for growth 12 °C, maximum 36 °C, optimal 27-30 °C. Colony surface at first white to cream coloured, later turning bay to chestnut with pale luteous to luteous periphery; flat, felty to cottony with abundant erect- aerial mycelium forming white patches; colony margins regular and filiform with abundant submerged mycelium. Reverse pale luteous, a blood sepia to chestnut coloured diffusible pigment is scarcely produced at 24 °C, pigment production is markedly enhanced at 27-30 °C, becoming greyish-sepia at 33 °C. Colonies on CMA and OA incubated at 24 °C in the dark reaching 65-67 mm diam. or occupying an entire 9 cm Petri dish in 7 d, respectively. Colony surface pale bay coloured, flat, felty to velvety, aerial mycelium scant, forming white to cream patches; margins regular. Reverse pale bay to pale vinaceous. Sporulation abundant from conidiophores formed on the substrate and aerial mycelium and from sporodochia. Conidiophores on the aerial mycelium straight or flexuous, erect or prostrate, septate, smooth- and thin-walled, often appearing rough by accumulation of extracellular material, commonly simple or reduced to conidiogenous cells borne laterally on hyphae or up to 200 μm tall and irregularly branched at various levels, branches bearing lateral and terminal monophialides borne mostly single or in pairs; phialides subulate, ampulliform, lageniform to subcylindrical, smooth- and thin-walled, (8.5 –)9.5–17.5(– 24.5) μm long, 2 –3(– 3.5) μm at the widest point, without periclinal thickening, collarets inconspicuous; conidia formed on aerial conidiophores, hyaline, obovoid, ellipsoidal to slightly reniform or allantoid, smooth- and thin-walled, 0-septate, (4.5 –)5–8.5(– 12.5) × (1.5 –)2–3.5(– 6) μm, clustering in discrete false heads at the tip of monophialides. Sporodochia pale orange to pink coloured, often somewhat translucent, formed abundantly on the surface of carnation leaves and on the agar surface. Conidiophores in sporodochia 26-46 μm tall, densely aggregated, irregularly and verticillately branched up to three times, with terminal branches bearing 2-3 monophialides; sporodochial phialides doliiform to subcylindrical, (9 –)11.5–15.5(– 18.5) × (2.5 –)3–4(– 4.5) μm, smooth- and thin-walled, with periclinal thickening and an inconspicuous apical collarette. Sporodochial conidia falcate, tapering toward the basal part, robust, moderately curved and slender; apical cell more or less equally sized than the adjacent cell, blunt to slightly papillate; basal cell papillate to distinctly notched, (1 –)3– 4-septate, hyaline, thin- and smooth-walled. One-septate conidia: 13 –17(– 18) × (2.5 –)3– 4 μm; two-septate conidia: 15 × 4.5 μm; three-septate conidia: (16 –)28.5–39(– 45) × (3 –)4–5(– 5.5) μm; four-septate conidia: 39.5 –40(– 41) × 4.5-5 μm; overall (13 –)27.5–39.5(– 45) × (3 –)3.5– 5.5 μm. Chlamydospores absent.

Distribution.

Madagascar, Niger and South Africa.

Etymology.

In honour and memory of Dr. Frederick J. Kruger, pioneer of forest hydrology, fynbos ecology and invasive species and fundamental for the collections included in this study.

Additional isolates examined.

Madagascar, from Striga hermonthica , unknown date, A.A. Abbasher, CBS 144210 = NRRL 26061 = BBA 70127. South Africa, Kruger National Park, Skukuza, Granite Supersite, 25°06'48.6"S, 31°34'36.5"E, from rhizosphere soil of Melhania acuminata , 23 Mar 2015, W.J. Swart, CBS 144495 = CPC 33746.

Notes.

This species is genetically closely related to F. dlaminii , both species having similar colonial morphology, optimal growth conditions and biogeography. Moreover, both species exhibit relatively short aerial phialides producing conidia in heads, somewhat resembling those produced by F. oxysporum rather than most members of the FFSC ( Leslie and Summerell 2006; Marasas et al. 1985). However, besides exhibiting much faster growth rates, F. fredkrugeri presents clearly distinctive morphological features such as the production of only one type of aerial conidia (vs. two types in F. dlaminii : allantoid to fusiform and 0-septate; and napiform 0-1-septate); orange to pink sporodochia, produced on carnation leaves but also abundantly on the agar surface (vs. orange sporodochia, produced only on the surface of carnation leaves in F. dlaminii ) ( Leslie and Summerell 2006). Additionally, F. fredkrugeri produces shorter and less septate sporodochial conidia ((1 –)3– 4-septate and up to 45 μm long in the latter species vs. mostly 5-septate and up to 54 μm long in F. dlaminii ) while chlamydospores are not produced. The latter feature, coupled with the somewhat more complex conidiophores also clearly differentiates F. fredkrugeri from F. oxysporum .