Alternaria guilanica Poursafar, Hashemlou, Ghosta, Salimi & Jav.

Poursafar, Alireza, Hashemlou, Esmaeil, Ghosta, Youbert, Salimi, Fatemeh & Javan-Nikkhah, Mohammad, 2021, Alternaria guilanica sp. nov., a new fungal pathogen causing leaf spot and blight on eggplant in Iran, Phytotaxa 520 (2), pp. 184-194 : 187-190

Alternaria guilanica Poursafar, Hashemlou, Ghosta, Salimi & Jav. -Nikkh., sp. nov. ( Figs. 1 , 2 )

Etymology: referring to the Iranian province from where the species was isolated.

Mycobank: MB838043

Description: Colonies on V8-A dark bluish green with off-white aerial mycelium, grey olivaceous at center with age, fast growing, 75 mm diam. after 7 days at 25ºC, loose cottony without conspicuous concentric zonation of growth and sporulation ( Fig. 2a ). Hyphae branched, septate, smooth or occasionally granular, hyaline to light brown to brown, superficial or submerged, 5–7.5 μm wide. Sporulation abundant, both from aerial hyphae or from hyphae growing directly on the agar surface ( Fig. 2b–c ). Conidiophores macronematous, solitary, straight or slightly curved, unbranched, septate, golden yellow to light brown to brown, 55–150 × 5–6 μm, with one or rarely two conidiogenous loci. Sometimes, hyphae coil up and form a hyphal ring-like structure bearing 3–5 conidiophores resulting in aggregated sporulation appearance under the stereomicroscope vision ( Fig. 2d–f ). Conidia enormous, solitary, rarely in a chain of two conidia, rostrate, straight or slightly curved, long narrow ellipsoid or mostly sub-cylindric, smooth or inconspicuously punctuate, golden to light brown to brown, with 5–11 (mostly 7–9) transverse disto- and eusepta, 0–3 longitudinal or oblique septa. Most conidia have only a single unbranched, hyaline, narrow-tapered beak, but rarely, the second shorter beak (10–80 µm in length) arise from the apical cell of the conidium. Mature conidium body reaches a size range of 50–135 × (10–)13–18(–20) μm. Beak length usually reaches into a range of (50–)70–180(–225) μm. Although the width of the base of the beak is ca 5–8 μm, it narrows to tips ca 2.5 μm. As long as only distosepta are present, the conidium body wall has no lateral constrictions, however it becomes moderately or conspicuously constricted at sites where the thickened and darkened transverse eusepta are formed ( Fig. 2g –z ). Sexual morph was not seen.

Typification: IRAN, Guilan province, Somehsara region , on Solanum melongena with leaf spot and blight symptoms, 12 Jul. 2019. M. Javan-Nikkhah, holotype IRAN 18093 F, ex-holotype culture IRAN 4220 C (GenBank accessions: MT 782297 , ITS; MT 786491 , GAPDH; MT 786497 , RPB2 ; MT 786500 , TEF1 -α; MT 786494 , Alt a 1) .

Additional specimens examined: IRAN, Guilan province, Somehsara region , on Solanum melongena with leaf spot and blight symptoms, 12 Jul. 2019. M. Javan-Nikkhah , IRAN 4221 C (GenBank accessions: MT 782298 , ITS; MT 786492 , GAPDH; MT 786498 , RPB2 ; MT 786501 , TEF1 -α; MT 786495 , Alt a 1). and IRAN 4222 C (GenBank accessions: MT 782299 , ITS; MT 786493 , GAPDH; MT 786499 , RPB2 ; MT 786502 , TEF1 -α; MT 786496 , Alt a 1) .

Notes: Alternaria guilanica is phylogenetically related to A. solani , A. grandis , A. protenta , A. dichondrae and A. paralinicola (formerly known as A. linicola ) ( Fig. 1 ). However, A. guilanica is differentiated morphologically from these species mainly by its mature conidia morphology including their size range, beak length/branching and the number of transverse septa (50–135 × 10–20 μm, beaks up to 225 μm with 0–1 branches and 7–9 transverse septa) compared to A. solani (conidia 80–115 × 16–26 μm, beaks up to 118 μm with 1–3 branches and 7–11 transverse septa), A. grandis (conidia 128–198 × 24–38 μm, beaks up to 200 μm commonly with 1–2 (–3) branches and 11–19 transverse septa), A. protenta (conidia 80–115 × 14–24 μm, beaks up to 135 μm commonly with 1–2 branches and 8–13 transverse septa), A. paralinicola (conidia 50–85 × 14–20 μm, beaks up to 160 μm with 1–3 branches and 5–12 transverse septa) and A. dichondrae (conidia 60–85 × 19–27 μm, beaks up to 110 μm with 1–4 branches and 7–10 transverse septa) ( Simmons 2007).

Pathogenicity test

The artificial inoculation of the eggplant leaves using mycelial plugs of three tested A. guilanica strains produced conspicuous necrotic lesions surrounded by chlorotic halos on the surface of leaves almost similar to the symptoms observed in the field ( Fig. 3a–g ). Re-isolation and re-identification of the inoculated strains confirmed the Koch’s postulates. No symptoms were formed on the controls ( Fig. 3h ).

Figures

FIGURE 1. Phylogenetic tree generated from Bayesian Inference (BI) based on the combined dataset of ITS-rDNA, GAPDH, RPB2, TEF1-α and Alt a 1 for 44 Alternaria strains. The Bayesian posterior probabilities (>0.75) and RAxML Maximum likelihood and Maximum parsimony bootstrap values (>50%) are given at the nodes (PP/ML/MP). The tree was rooted to A. gypsophilae CBS 107.41 and A. vaccariae CBS 116533 (Alternaria sect. Gypsophilae) and the newly identified strains are in bold.

FIGURE 2. Alternaria guilanica (IRAN 4220C). a. Colony on V8-A after 7 days. b–c. sporulation pattern on V8-A. d–f. Conidiophores. g–x. conidia. Bars = 20 μm.

FIGURE 3. a–g. Symptoms formed on eggplant leaves 7–10 days after inoculation in greenhouse conditions (a, b: strain IRAN 4220C; c–e: strain IRAN 4222C; f, g: strain IRAN 4221C) h. Control treatment.