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

Fig. 5

Holotype.

China, Hunan Province, Yiyang City, Longqiao Town, 28°27'24"N, 112°29'7"E, isolated from leaf spots of Cunninghamia lanceolata , May 2017, Wen-Li Cui, (holotype: CFCC 59356). Holotype specimen is a living specimen being maintained via lyophilisation at the China Forestry Culture Collection Center (CFCC). Ex-type (HN43-10-2) is maintained at the Forest Pathology Laboratory, Nanjing Forestry University.

Etymology.

Epithet is after Longqiao Town, Yiyang City, Hunan Province where the type specimen was collected.

Host/distribution.

From C. lanceolata in Longqiao Town, Yiyang City, Hunan Province, China.

Description.

Mycelium superficial on the PCA medium, composed of septate, branched, smooth, thin-walled, white to light brown hyphae. Conidiophores macronematous, mononematous, solitary, subcylindrical, branched or unbranched, straight or geniculate, (12.7-)18.4-41.8(-65.0) × (2.5-)3.3-4.7(-5.2) μm, (mean ± SD = 30.1 ± 11.7 × 4.0 ± 0.7 μm, n = 45). Each conidiogenous locus bears a primary chain of 3-7 conidia; each chain usually has a secondary chain of 1-2 conidia. Conidiogenous cells apical or subapical, cylindrical, light brown, smooth, (2.9-)4.6-9.5(-13.6) × (1.8-)3.0-4.5(-6.3) μm, (mean ± SD = 7.0 ± 2.5 × 3.8 ± 0.8 μm, n = 46), mono- or polytretic. Newly developed conidia subhyaline or pale greyish, ellipsoidal or subacute, thin-walled, with few or no protuberance. Mature conidia pale brown to brown, ovoid or ellipsoid to long-ellipsoid, pyriform, usually smooth. Conidial bodies (10.0-)16.7-28.8(-39.3) × (5.9-)8.2-12.6(-14.8) μm, (mean ± SD = 22.7 ± 6.0 × 10.4 ± 2.2 μm, n = 49), with 1-4 transverse and 0-2 longitudinal septa. 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, (2.8-)2.9-21.7(-41.7) × (2.5-)2.8-4.3(-6.2) μm, (mean ± SD = 12.3 ± 9.4 × 3.5 ± 0.7 μm, n = 37). Conidial beakless 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 ± 0.1 mm/d; aerial hypha cottony, pale gray to greyish-green, with white to pale grey margins; reverse centre brownish to dark green with pale grey margins; sporulation sparse; diffusible pigment absent.

Additional materials examined.

China, Hunan Province, Yiyang City, Longqiao Town , 28°27'24"N, 112°29'7"E, isolated from leaf spots of Cunninghamia lanceolata , May 2017, Wen-Li Cui, HN 43-10-2-1, HN43-10-2-2, HN43-10-2-3, HN43-10-2-4 .

Notes.

The isolates of A. hunanensis were phylogenetically close to A. longqiaoensis (this study, HN43-14), A. vaccinii (ex-type, CBS 118818), A. platycodonis (ex-type, CBS 121348), A. rhadina E.G. Simmons (ex-type, CBS 595.93), A. citriarbusti (ex-type, CBS 102598) and A. tomaticola (ex-type, CBS 118814) (Fig. 2 ). Between A. hunanensis isolates and A. longqiaoensis HN43-14, there were 2/453 differences in Alt a1, 3/510 in ITS, 2/401 in endoPG, 2/757 in RPB2 and 18/996 in SSU. Between A. hunanensis isolates and A. vaccinii (ex-type, CBS 118818), there were 4/453 differences in Alt a1, 2/499 in GAPDH, 3/510 in ITS and 3/401 in endoPG. Between A. hunanensis isolates and A. platycodonis (ex-type, CBS 121348), there were 1/453 differences in Alt a1, 2/499 in GAPDH, 3/510 in ITS and 2/401 in endoPG. Between A. hunanensis isolates and A. rhadina (ex-type, CBS 595.93), there were 1/453 differences in Alt a1, 2/499 in GAPDH, 3/510 in ITS and 2/401 in endoPG. Between A. hunanensis isolates and A. citriarbusti (ex-type, CBS 102598), there were 1/453 differences in Alt a1, 2/499 in GAPDH, 3/510 in ITS and 2/401 in endoPG. Between A. hunanensis isolates and A. tomaticola (ex-type, CBS 118814), there were 3/453 differences in Alt a1, 2/499 in GAPDH, 3/510 in ITS and 2/401 in endoPG. The PHI analysis showed that there was no significant recombination between A. hunanensis isolates and its related species (Φw = 0.3502) (Fig. 2B ). Distinguishing characteristics of this new species and other morphologically related species of Alternaria spp. are shown in Table 2 . Morphologically, sporulation patterns of the A. hunanensis isolates were different from those of A. longqiaoensis HN43-14 (one secondary chain of 1-2 conidia vs. 1-3 further branching chains (secondary, tertiary and quaternary chains) of 3-4 conidia). Conidia in chains of the A. hunanensis isolates were less than those of A. vaccinii CBS 118818 (ex-type) (3-7 vs. 8-10 conidia) ( Simmons 2007), A. platycodonis CBS 121348 (ex-type) (3-7 vs. 8-10 conidia) ( Zhang 2003), A. rhadina CBS 595.93 (ex-type) (3-7 vs. 9-15 conidia) ( Simmons 1993) and A. tomaticola CBS 118814 (ex-type) (3-7 vs. 10-15 conidia) ( Simmons 2007). Transverse septa of conidia of the A. hunanensis isolates were less than those of A. citriarbusti CBS 102598 (ex-type) (1-4 vs. 6-11 transverse septa) ( Simmons 1999). Thus, the phylogenetic and morphological evidence supports 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 5. Alternaria hunanensis (HN 43 - 10 - 2) A colony on PCA after 6 days at 25 ° C in the dark B, C sporulation patterns D, E conidiophores and conidiogenous cells F conidia. Scale bars: 50 μm (B, C); 10 μm (D-F).