Fusarium madaense Ezekiel, Sand.-Den., Houbraken & Crous, 2020

Ezekiel, Chibundu N., Kraak, Bart, Sandoval-Denis, Marcelo, Sulyok, Michael, Oyedele, Oluwawapelumi A., Ayeni, Kolawole I., Makinde, Oluwadamilola M., Akinyemi, Oluwatosin M., Krska, Rudolf, Crous, Pedro W. & Houbraken, Jos, 2020, Diversity and toxigenicity of fungi and description of Fusarium madaense sp. nov. from cereals, legumes and soils in north-central Nigeria, MycoKeys 67, pp. 95-124 : 95

Fusarium madaense Ezekiel, Sand.-Den., Houbraken & Crous sp. nov. Figure 5

Diagnosis.

Different from F. thapsinum by the absence of napiform microconidia. Different from F. andiyazi , F. thapsinum and F. verticillioides by its lighter colony pigmentation, growth rates, microconidial septation, presence of true chlamydospores and secondary metabolite patterns.

Type.

Nigeria, Nasarawa, Mada Station, from groundnut ( Arachis hypogaea ), Sep. 2018, C.N. Ezekiel, holotype CBS H-24346, ex-holotype strain CBS 146669 = CPC 38344 = 12B(3)2.

Description.

Colonies grown in the dark at 24°C. On MEA and PDA with an average radial growth rate of 5.9-6.5 mm/d and filling an entire 90 mm Petri dish in 7 d. Surface white to pale rosy buff, flat, velvety to felty with abundant patches of white aerial mycelium; margin regular, filiform. Reverse pale saffron to peach, a pale bay diffusible pigment can be scarcely produced. On OA, occupying an entire 90 mm Petri dish in 7 d. Surface white to pale rosy buff, flat, velvety to felty with abundant patches of white aerial mycelium; margin regular. Reverse pale luteous to saffron. On SNA, reaching 24-25 mm diam. in 7 d. Surface white, velvety, with scarce aerial mycelium, margins filiform. Reverse white.

Conidiophores on aerial mycelium straight, erect, septate, smooth- and thin-walled, commonly simple or reduced to conidiogenous cells, borne laterally on hyphae or laterally branched at various levels, bearing terminal single monophialides; phialides subulate to subcylindrical, smooth- and thin-walled, (17-)25.5-39.5 μm long, (2-)2.5-3.5 μm at widest point, periclinal thickening and collarettes inconspicuous or absent; microconidia hyaline, clavate, smooth- and thin-walled, 0-3-septate, (7-)9-15(-21) × (2-)2.5-4(-5) μm, arranged in long chains at the tip of monophialides. Sporodochia pale to bright orange, formed abundantly on the surface of carnation leaves and on agar surface. Conidiophores in sporodochia, 21-60 μm tall, simple or irregularly and verticillately branched, bearing terminal, single monophialides or groups up 2-3 monophialides; sporodochial phialides doliiform to subcylindrical, (10.5-)13-18(-20.5) × (2.5-)3-4(-4.5) μm, smooth- and thin-walled, with conspicuous periclinal thickening and an often short apical collarette. Sporodochial conidia lunate to falcate, tapering towards apical and basal ends, moderately curved dorsiventrally or with an almost straight ventral part; apical cell more or less equally sized than the adjacent cell, apically slightly elongated to papillate; basal cell distinctly notched, (0-)1-5(-6)-septate, hyaline, thin- and smooth-walled. Aseptate conidia : (38-)38.5-42(-44) × 3.5-4.5 μm; one-septate conidia : (37.5-)40-48(-53) × 3.5-4(-4.5) μm; two-septate conidia : 43 × 3.7 μm; three-septate conidia : (29-)38-48.5(-61.5) × (3-)4-4.5(-5) μm; four-septate conidia : (45-)46.5-54(-59) × (3.5-)4-4.5(-5) μm; five-septate conidia : 47.5-55.5(-60) × 4-4.5 μm; six-septate conidia : 55.5 × 4.5 μm; overall (29-)38.5-50(-61.5) × (3-)4-4.5(-5) μm. Chlamydospores present on MEA, PDA and SNA, globose to subglobose, hyaline, smooth and thick-walled, (6-)6.5-8.5(-10) μm diam., terminal or intercalary in the aerial hyphae, solitary or in chains

Distribution.

Nigeria.

Etymology.

Name refers to Mada Station, a locality in Nasarawa State, Nigeria, where the species was found.

Additional isolates examined.

Nigeria, Mada Station, from groundnut ( Arachis hypogaea ), Sept 2018, C.N. Ezekiel, CBS 146648 = CPC 38321 = 12B(3), CBS 146656 = CPC 38330 = 12B(5); from sorghum, Jan 2019, C.N. Ezekiel, CBS 146651 = CPC 38324 = 7S(6).

Notes.

Although clearly recognisable based on genetic markers, Fusarium madaense is hardly distinguishable from its closer relatives, based on morphological features only. The novel species is characterised by abundant long, slender and slightly curved macroconidia, a morphology typical of the FFSC. The overall morphology of F. madaense is similar to that of F. andiyazi , F. thapsinum and F. verticillioides ; all species are characterised by clavate microconidia formed in long chains from relatively long monophialides. Moreover, the four mentioned species are known to be pathogenic on sorghum ( Leslie and Summerell 2006) and have been isolated here from the same geographical regions. Nevertheless, some morphological features of F. madaense can provide an indication of its identity. These include a pale saffron colony pigmentation on OA and PDA, not developing the intense purple colour typical of F. andiyazi and F. verticillioides , nor the yellow pigmentation of F. thapsinum ; the presence of up to 3-septate clavate microconidia vs. the up to 2-septate and aseptate microconidia of F. andiyazi and F. verticillioides , respectively; and the aseptate, but also rarely napiform microconidia of F. thapsinum ( Nirenberg 1976, Klittich et al. 1997, Marasas et al. 2001). In addition, F. madaense can be differentiated from F. andiyazi , its closest morphological and phylogenetic relative, by its slightly faster growth rates on PDA, somewhat wider macroconidia and the presence of true chlamydospores.

The proposal of the novel species F. madaense and its differentiation from F. andiyazi , F. thapsinum and F. verticillioides is also supported by secondary metabolite profiling of all the above-mentioned species, as found in this study. Fusarium madaense was the only beauvericin-producing species in our dataset. Nevertheless, it has been reported that F. verticillioides strains can produce trace levels of this toxin ( Leslie et al. 2004, Leslie and Summerell 2006). The alpha-pyrones deoxyfusapyron and fusapyron were produced only by F. madaense and its closest relative F. andiyazi ; by contrast, fusarin C was produced by F. madaense , F. thapsinum and F. verticillioides , but not by F. andiyazi .

Figures

Figure 5. Fusarium madaense sp. nov. (ex-type culture CBS 146669). A-C aspect of colonies on PDA, OA and SNA, respectively, after 14 d at 24 ° C in the dark D colony reverse on OA (up) and PDA (down) after 14 d at 24 ° C in the dark E-G, J aerial conidiophores and phialides H, I sporodochia formed on the surface of carnation leaves K, L sporodochial conidiophores M, N chlamydospores O, P microconidia Q sporodochial conidia. Scale bars: 100 μm (H, I); 20 μm (J); 10 μm (all others).