Alternaria dongshanqiaoensis Lin Huang, Jiao He & D.W. Li, 2024

He, Jiao, Li, De-Wei, Cui, Wen-Li & Huang, Lin, 2024, Seven new species of Alternaria (Pleosporales, Pleosporaceae) associated with Chinese fir, based on morphological and molecular evidence, MycoKeys 101, pp. 1-44 : 1

Alternaria dongshanqiaoensis Lin Huang, Jiao He & D.W. Li sp. nov.

Fig. 4

Holotype.

China, Jiangsu Province, Nanjing City, Dongshanqiao Forest Farm, 31°51'11"N, 118°46'12"E, isolated from leaf spots of Cunninghamia lanceolata , May 2017, Wen-Li Cui, (holotype: CFCC 59353). Holotype specimen is a living specimen being maintained via lyophilisation at the China Forestry Culture Collection Center (CFCC). Ex-type (DSQ2-2) is maintained at the Forest Pathology Laboratory, Nanjing Forestry University.

Etymology.

Epithet is after Dongshanqiao Forest Farm, Nanjing City, Jiangsu Province where the type specimen was collected.

Host/distribution.

from C. lanceolata in Dongshanqiao Forest Farm, Nanjing City, Jiangsu Province, China.

Description.

Mycelium superficial on the PCA, composed of septate, branched, smooth, thin-walled, white to pale brown hyphae. Conidiophores macronematous, mononematous, solitary and relatively short, pale brown, smooth, 1-3 septate, (8.1-)16.4-60.2(-100.5) × (2.4-)3.2-4.6(-5.6) μm, (mean ± SD = 38.3 ± 21.9 × 3.9 ± 0.7 μm, n = 30), arising mostly at right angles from undifferentiated hyphae. Conidiogenous cells apical or subapical, cylindrical, light brown, smooth, (3.8-)5.2-13.7(-20.2) × (2.8-)3.5-4.6(-5.2) μm, (mean ± SD = 9.4 ± 4.2 × 4.0 ± 0.5 μm, n = 36), mono- or di-tretic, with conspicuous scars at the loci of sporulating after conidia have seceded. Each conidiogenous locus bears a primary chain of 5-9 conidia; rarely with lateral branches or occasionally a sole secondary conidium. Conidial bodies brown to dark brown, ellipsoid to obclavate, smooth to verruculose, (16.4-)21.1-32.9(-40.1) × (10.2-)11.4-16.8(-22.2) μm, (mean ± SD = 27.0 ± 5.9 × 14.1 ± 2.7 μm, n = 48), with 1-4 (mostly 3) transverse and 1-4 longitudinal septate. Secondary conidia commonly produced by means of a short apical or lateral secondary conidiophore, but rarely by conidia through an inconspicuous apical conidiogenous locus. Secondary conidiophores (false beaks) at the apical end and median of conidium, short, mostly single-celled, (1.4-)2.2-9.4(-20.0) × (1.9-)2.8-4.0(-5.2) μm, (mean ± SD = 5.8 ± 3.6 × 3.4 ± 0.6 μm, n = 33). Beakless conidia mostly with a conical cell at the apex. Chlamydospores not observed.

Culture characteristics.

Colonies on PCA incubated at 25 °C in the dark growing at 7.8 ± 0.2 mm/d; aerial hyphae cottony, greyish-green, with grey margins; reverse centre black, with white margins.

Additional materials examined.

China, Jiangsu Province, Nanjing City, Dongshanqiao Forest Farm, 31°51'11"N, 118°46'12"E, isolated from leaf spots of Cunninghamia lanceolata , May 2017, Wen-Li Cui, DSQ2-2-1, DSQ2-2-2, DSQ2-2-3, DSQ2-2-4 ; Hunan Province, Yiyang City, Longqiao Town , 28°27'24"N, 112°29'7"E, isolated from leaf spots of C. lanceolata , May 2017, Wen-Li Cui, HN 43-6-1, HN43-6-1-1, HN43-6-1-2, HN43-6-1-3, HN43-6-1-4 .

Notes.

The isolates of A. dongshanqiaoensis were phylogenetically close to A. citri (ex-epitype, CBS 107.27), A. cinerariae (ex-epitype, CBS 612.72), A. kikuchiana (ex-holotype, CBS 107.53) and A. tenuissima (Kunze) Wiltshire (ex-epitype, CBS 620.83) (Fig. 2 ). Between A. dongshanqiaoensis isolates and A. citri (ex-epitype, CBS 107.27), there were 2/453 differences in Alt a1, 4/510 in ITS, 2/401 in endoPG, 1/757 in RPB2 and 2/996 in SSU. Between A. dongshanqiaoensis isolates and A. cinerariae (ex-epitype, CBS 612.72), there were 2/453 differences in Alt a1, 4/510 in ITS, 2/401 in endoPG, 1/757 in RPB2 and 2/996 in SSU. Between A. dongshanqiaoensis isolates and A. kikuchiana (ex-type, CBS 107.53), there were 2/453 differences in Alt a1, 4/510 in ITS, 8/664 in OPA10-2, 3/401 in endoPG, 2/757 in RPB2 and 2/996 in SSU. Between A. dongshanqiaoensis isolates and A. tenuissima (ex-epitype, CBS 620.83), there were 1/453 differences in Alt a1, 6/510 in ITS, 8/664 in OPA10-2, 3/401 in endoPG, 1/757 in RPB2 and 6/996 in SSU. The PHI analysis showed that there was no significant recombination between A. dongshanqiaoensis isolates and its related species (Φw = 0.1647) (Fig. 2A ). Distinguishing characteristics of this new species and other related species of Alternaria spp. are shown in Table 2 . Morphologically, conidia in chains of the A. dongshanqiaoensis isolates were more than those of A. citri CBS 107.27 (ex-epitype) (5-9 conidia vs. 3-6 conidia) ( Pierce 1902). Conidia of the A. dongshanqiaoensis isolates were significantly different from those of A. cinerariae CBS 612.72 (ex-epitype) (21.1-32.9 × 11.4-16.8 μm vs. 18-295 × 8-63 μm) ( Nishikawa and Nakashima 2020). Longitudinal septa of conidia of the A. dongshanqiaoensis isolates were less than those of A. kikuchiana CBS 107.53 (ex-holotype) (1-4 vs. 1-10 longitudinal or oblique septa) ( Nishikawa and Nakashima 2019). Conidia of the A. dongshanqiaoensis isolates were different from those of A. tenuissima CBS 620.83 (ex-epitype) (beakless vs. with a narrow-taper beak) ( Wiltshire 1933). In conclusion, the phylogenetic and morphological evidence support this fungus as being a new species within the Alternaria alternata species complex.

Figures

Figure 2. Splitgraphs showing the results of the pairwise homoplasy index (PHI) test of newly described taxa and closely-related species using both LogDet transformation and splits decomposition A the PHI of Alternaria xinyangensis sp. nov. and A. dongshanqiaoensis sp. nov. with their phylogenetically related isolates or species B the PHI of A. shandongensis sp. nov., A. kunyuensis sp. nov., A. hunanensis sp. nov. and A. longqiaoensis sp. nov. with their phylogenetically related isolates or species C the PHI of A. cunninghamiicola sp. nov. with their phylogenetically-related isolates or species. PHI test value (Φw) <0.05 indicate significant recombination within a dataset. * indicates strains of this study. T indicates the ex-type strains, ET indicates the ex-epitype strains, HT indicates the ex-holotype strains.

Figure 4. Alternaria dongshanqiaoensis (DSQ 2 - 2) A colony on PCA after 6 days at 25 ° C in the dark B, C sporulation patterns D conidiophore and conidiogenous cell E conidia. Scale bars: 50 μm (B, C); 10 μm (D, E).