Phyllactinia sennae R. Gregorio-Cipriano, Ramos & D. González, 2025

Gregorio-Cipriano, Rosario & Ramos, Antero, 2025, Phyllactinia passiflorae-adenopodae, and Phyllactinia sennae (Erysiphaceae), two new powdery mildew species found in Mexico, Phytotaxa 711 (2), pp. 183-194 : 188-189

Phyllactinia sennae R. Gregorio-Cipriano, Ramos & D. González , sp. nov. ( Figs. 4 , 5 ).

MycoBank: 856060

Diagnosis: Phyllactinia sennae resembles to Ovulariopsis leucanae but it is easily differentiated by having wider primary conidia, (11–)13–19(–22) μm, and conidiophores with strongly helicoidal basal cells, and a basal septum elevated more than 9 µm.

Etymology: Epithet derived from host genus, Senna .

Holotype:— MEXICO, Veracruz, Xalapa, Botanical Garden Francisco Javier Clavijero, on Senna didymobotrya ( Fabaceae ), 1895 m elev., 19°51'18.36"N, 102° 3'15.58"W, September 1, 2023, Gregorio 711 (XAL); Isotype EBUM 28791. GenBank accession number: PQ427273 (ITS).

Description: Mycelia internal and external, external mycelium amphigenous, effuse, forming a thin white or greyish layer. Colony associated with a central necrosis, seen in the upper side of the leaf. Superficial hyphae straight to sinuous, branched, septate, 3–8 μm wide, hyaline, thin walled. Hyphal appressoria solitary, nipple-shaped, oblong, hooked to lobed, 4–6 μm diameter. Conidiophores arising from superficial hyphae, position usually not in the middle between two septa of the mother cell, erect, basal septum mostly elevated over the junction with the supporting hypha, about 9–17 μm. Foot cells (41–)68–165(–182) × 4–7 μm, mainly helicoidal, sometimes slightly sinuous to flexuous or rarely straight, followed by 2–3(–4) shorter cells, 35–66(–71) μm long; forming conidia singly. Conidia dimorphic, primary conidia lanceolate to narrowly ellipsoid or ellipsoid-obovoid, apex pointed to rounded, base truncate to rounded, (43–)52–78(–82) × (11–)13–19(22) μm; secondary conidia clavate, rarely ovoid-clavate, apex broadly rounded, base almost truncate, (48–)58–71 × 12–15(–17) μm. Germ tubes near the base or apex, filiform, short to moderately long, straight to sinuous, two lobed at the tip.

Teleomorph not found.

Additional Material examined:— MEXICO, Michoacan, Chilchota, Ichán, on S. didymobotrya , 1895 m elev., 19°51'18.36"N, 102°3'15.58"W, November 10, 2020, Gregorio 699 (XAL). GenBank accession number: PQ427274 (ITS).

Comments:— Ph. sennae is the first Phyllactinia species reported infecting Senna in Mexico. There are three Phyllactinia species known to infect three other genera of Fabaceae in the country ( Table 3). Only Phyllactinia cassiae-fistulae U. Braun & Y.S. Paul , of about 20 species of Phyllactinia infecting legumes worldwide, have been found on Senna siamea (Lam.) H.S. Irwin & Barneby in Southeast Asia ( Braun & Cook 2012, Monkhung et al. 2013, Meeboon et al. 2018).

Figures

FIGURE 4. Phyllactinia sennae on Senna didymobotrya. A Conidiophores, B–C Conidia. Bars = 25 µm.

FIGURE 5. Phyllactinia sennae. A Primary conidia, B Secondary conidia, C Conidiophores, D Conidium germination, E Hyphal appressoria. Bars = 10 µm.