Fusarium clavum J.W. Xia, L. Lombard, Sand.-Den., X.G. Zhang & Crous, Persoonia 43: 199 (2019)

Index Fungorum number: IF 833468;  MycoBank number: MB 831833; Facesoffungi number: FoF 09578; Fig. 1

Saprobic on dead stalk of Sorghum bicolor. Sexual morph Undetermined. Asexual morph Sporodochia salmon to orange, formed abundantly on carnation leaf pieces. Conidiophores densely and irregularly branched. Conidiogenous cells monophialides, subulate to subcylindrical, smooth, thin walled. Conidia 25–35×3–4 μm, falcate, slender, curved dorsiventrally, tapering towards both ends, with elongated or whip-like curved apical cells, mostly 3-septate, hyaline, smooth-walled. Chlamydospores 6–12 μm diam., abundant, globose, subglobose to oval, subhyaline to yellowish-brown, smooth-walled, terminal or intercalary, solitary, in pairs or forming chains.

Culture characteristics – Colonies on PDA reaching 90 mm at 24 °C after 28 d; surface cinnamon, flat, velvety, with scant aerial mycelium; reverse cinnamon. On SNA and WA colonies sparse and flat, without colour, sporulation moderate on the surface of the agar and the carnation leaf pieces.

Material examined – AUSTRALIA, Brookstead, on dead stalk of Sorghum bicolor, 19 February 2018, N. Vaghefi, BRIP 70756a, new record.

GenBank numbers – CAL = MW403051, RPB1 = MW403052, RPB2 = MW403053, TEF1-α=MW403054.

Notes – Fusarium clavum belongs to the Fusarium incarnatum-equiseti species complex (Wang et al. 2019a; Xia et al. 2019). In a three-locus phylogeny (Fig. 2), the isolate (BRIP 70756a) was recovered in a well-supported clade (99% MLBS, 1.00 BYPP) with the type strain F. clavum (CBS 126202). Fusarium clavum has been reported from various plants, human organs, and soil in Africa, Europe, Asia, and the USA (Xia et al 2019; Matic et al. 2020). Although the isolate (BRIP 70756a) was isolated from stalk rot on S. bicolor, the pathogenicity of this isolate has not been established (Fig. 1). This is the first record of F. clavum on S. bicolor, and the first record of this fungus in Australia.

Figure 1 – Fusarium clavum (BRIP 70756a, new record). a, b Culture on PDA from surface and reverse. c, d Conidia and chlamydospores. Scale bars: a, b=1 cm, c, d=10 µm

Figure 2 – Phylogram generated from Bayesian analysis based on combined CAL, RPB2, and TEF1-α sequence data representing Fusarium incarnatum-equiseti species complex and related taxa. The second measure of branch support was obtained through Maximum Likelihood (ML) analysis of the same alignment using RAxML v. 8 (Stamatakis 2014) based on the GTR substitution model with gamma-distribution rate variation for each partition. Reference sequence were obtained from Xia et al. (2019). The tree is rooted to Fusarium concolor (NRRL 13459). The analysis was performed using MrBayes v. 3.2.4 (Ronquist et al. 2012) based on the K80, K80+G, and HKY+G nucleotide substitution models selected for CAL, RPB2, and TEF1-α, respectively, using PAUP v. 4.0 (Swofford 2003) and MrModeltest v. 2.3. (Nylander 2009). Maximum likelihood bootstrap support values (MLBS) greater than 80% are placed above the nodes and Bayesian posterior probabilities (BYPP) equal to or greater than 0.95. Branches with MLBS=100% and BYPP=1.00 are thickened. Scale bar indicates the number of substitutions per nucleotide. Ex-type strains are in bold and newly isolate is in blue