Diaporthe longicolla (Hobbs) J.M. Santos, Vrandečić & A.J.L. Phillips, in Santos, Vrandečić, Čosić, Duvnjak & Phillips, Persoonia 27: 13 (2011)

Index Fungorum number: IF 563213; MycoBank number: MB563213; Faceoffungi number: FoF 11682; Figs. 1, 2

Pathogenic and associated with stem of Vigna unguiculata. Sexual morph: Not observed. Asexual morph: Conidiomata 80–130 µm high, 230–320 µm diam. x̄ = 118 × 290 μm, n = 20, 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 4–7 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 4–7×4.1–7.3 μm (x̄ =4.4 × 6.3 μm, n=30), ampulliform, straight to sinuous, unbranched, hyaline, smooth. Conidiogenous cells 7.8–13.8 × 1.4–2.7 μm (x̄ =10.9 × 2.1 μm, n=30), phialidic, terminal, cylindrical, slightly tapering towards the apex. Alpha-conidia 5.1–7.5×1.2–3.4 μm (x̄ =6.1×2.6 μm, n=20), aseptate, hyaline, smooth, ovate to ellipsoidal, guttulate. Beta-conidia 5.8–7.5×2.5–3.5 μm (x̄ =6.4×2.8 μm, n=10), hyaline, filiform, hamate.

Cultural characteristics – On potato dextrose agar, the fungus initially produced white fluffy aerial hyphae, forming relatively dense concentric pattern colony, which subsequently exhibited light yellow pigmentation.

Material examined – India, Karnataka, Mysuru Doddamaragowdanahally, on infected stem of cowpea plants as pathogen. July, 2020, S. Mahadevakumar, Y.S. Deepika (UOM-IOE 20/25), living cultures CPDl21, CPDl22, MKSVu012.

Hosts – Wide host range, including Abutilon, Acer, Actinidia, Ambrosia, Arachis, Chamaesyce, Cucumis, Euphorbia, Glycine, Helianthus, Ipomoea, Kalanchoe, Phaseolus, Pisum, Pyrus, Rumex, Solanum, Trichilia, Vigna and Xanthium (Farr and Rossman 2022; this study).

Distribution – Wide geographical range, including in Argentina, Australia, Brazil, China, Croatia, Greece, India, Italy, Malaysia, Missouri, South Korea, US (Farr and Rossman 2022; this study).

GenBank Numbers – CPDl21—MW737797 (ITS), OM934823 (tub2), OM934820 (tef1) CPDl22–MW737798 (ITS), OM934824 (tub2), OM934821(tef1) MKSVu012– KT819767 (ITS), OM934825(tub2), OM934822 (tef1)

Notes – The symptoms were observed on stems of cowpea. Initial symptoms appeared as small lesions, more or less circular, later elongated, blackish-brown lesions, eventually pycnidia developed (Fig. 1). Stem girdling occurs and the shoot above the infected area wilts and dries up. Pathogenicity tests were conducted and proved to be pathogenic on healthy cowpea plants. Morphologically our strain shares similar morphology with the ex-type strain of D. longicolla (Fig. 2). In the multigene phylogenetic analyses, our strain clusters with D. longicolla with a high bootstrap support (Fig. 3). Previously, Phomopsis longicolla is known to be associated with cowpea seeds. However, no reports are available on the association of D. longicolla of cowpea in India. This is the first report of D. longicolla associated with cowpea from India.

Figure 1 – Micromorphological features of D. longicolla (CPDl21, new host record) a. Cowpea stem affected by Diaporthe longicolla. b. Stereo view of infected region showing pycnidial structures. c–d. Stereo view showing cirri of spores erupted from pycnidia. e. SEM image of pycnidium. f. Conidia of D. longicolla observed in SEM. Scale bars: b=10 mm; c– d=2 mm; e – f=10 µm

Figure 2 – Micromorphological features of D. longicolla: a–d. Conidial mass with spores observed under compound microscope. e–g Beta conidia of Diaporthe longicolla recorded on cowpea plant

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)