Diaporthe phaseolorum (Cooke & Ellis) Sacc., Syll. Fung. (Abellini) 1: 692 (1882).
Index Fungorum number: IF164797; MycoBank number: MB164797; Faceoffungi number: FoF 10638; Figs: 1, 2.
Pathogenic and associated with stem of Vigna unguiculata. Sexual morph: Not observed. Asexual morph: Conidiomata 105–192 µm high, 165–285 µm diam. x̄ =122×255 μm, n = 30, pycnidial, pyriform, initially immersed, erumpent at maturity, globose to pyriform, black, elongated neck, often with light yellowish white conidial cirrus extruding from ostiole. Pycnidial wall parenchymatous consisting of 3–6 layers of pale brown, thick-walled cells of textura angularis. Pycnidia globose locules and prominent beaks, which immersed in medium, black, solitary, discoid or irregular. Conidiophores 3.8–7.5×3.8–7.5 μm (x̄ =4.2×5.8 μm, n=30), ampulliform, straight to sinuous, unbranched, hyaline, smooth. Conidiogenous cells 8.2–12.8 × 1.6–2.5 μm (x̄ =9.8 × 2.2 μm, n=30), phialidic, terminal, cylindrical, slightly tapering towards the apex. Alpha-conidia 5.3–7.7×1.5–4.6 μm (x̄ =6.5×2.8 μm, n=30), aseptate, hyaline, smooth, ovate to ellipsoidal, guttulate. Beta-conidia 10.2–17.5×1.2–2.3 μm (x̄ =12.6×1.2 μm, n=30), hyaline, filiform, hamate.
Culture characteristics – On PDA, colonies with white, floccose, aerial mycelium were recorded after 7 days of incubation. Pure cultures obtained from the colonies expressed from infected pod and stem samples.
Material examined – India, Karnataka, Mysuru Doddamaragowdanahally, on infected stem of cowpea plants as pathogen, July, 2020, S. Mahadevakumar, Y.S. Deepika, N. Lakshmidevi (UOM-IOE 20/26), living cultures CPDp1, CPDp2.
Hosts – Wide host range, including Acer, Actinidia, Aeschynomene, Arctium, Aspalathus, Aster, Calopogonium, Cannabis, Caperonia, Capsicum, Centrosema, Clitoria, Cyphomandra, Desmanthus, Desmodium, Eriobotrya, Euphorbia, Glycine, Helianthus, Hylocereus, Ipomoea, Jatropha, Lablab, Lupinus, Lycopersicon, Macroptilium, Macrotyloma, Maytenus, Ocimum, Olearia, Panicum, Phalaris, Phaseolus, Pyrus, Stokesia, Vigna, Vitis and Zea (Farr and Rossman 2022; this study).
Distribution – Wide geographical range, including in Australia, Barbados, Brazil, Brunei Darussalam, Cameroon, Canada, China, Colombia, Cook Islands, Croatia, Cuba, Dominican Republic, Fiji, India, Italy, Jamaica, Korea, Maryland, Mauritius, Missouri, New Zealand, Papua New Guinea, Spain, South Africa, Switzerland, Thailand, Tonga, Trinidad and Tobago, United Kingdom, United States, Uruguay, Venezuela and West Indies (Farr and Rossman 2022; this study).
GenBank Numbers – CPDp1– MW737799 (ITS), OM934818 (tub2), OM934816 (tef1) CPDp2– MW737800 (ITS), OM934819 (tub2), OM934817 (tef1)
Notes – Morphologically our strain is similar to the extype strain of D. phaseolorum (Fig. 1). In the multigene phylogenetic analyses, our strain clustered with the ex-type strain of D. phaseolorum (Fig. 3). Pathogenicity tests were conducted and proved to be pathogenic on healthy cowpea plants. Diaporthe longicolla causes stem blight of cowpea while D. phaseolorum causes pod blight of the same host (Fig. 2). This is the first report of D. phaseolorum associated with cowpea from India and worldwide.
Figure 1 – Diagnostic features of cowpea stem blight and pod blight disease caused by Diaporthe phaseolorum and D. longicolla: a–b. field view of cowpea plants affected with Diaporthe stem blight and pod blight disease. c, d, g. Stem blight disease caused by D. longicolla. e,f,h,i. pod blight disease symptoms caused by D. phaseolorum
Figure 2 – Cultural and micromorphological characteristics of Diaporthe phaseolorum isolated from Cowpea: a–c. Pure cultures of D. phaseolorum on PDA (15 days old). d–f. Alpha conidia of D. phaseolorum. Scale bar: d–f=10 µm
Figure 3 – Phylogram generated from maximum likelihood analysis based on ITS, cal, his, tef1 and tub2 sequenced data of given Diaporthe species. Related sequences were obtained from GenBank, and 223 strains are included in the sequence analyses, with 2674 columns, 1972 distinct patterns 1439 parsimony-informative, 340 singleton sites, 894 constant sites. Diaporthella corylina (CBS121124) is used as the outgroup taxon. Bootstrap support values for ML ≥65%, BYPP ≥0.90 are given near the nodes. Type strains are in bold. Newly generated strains are in red bold
Figure 3 – (continued)