Meliola konniensis Jacob Thomas & G. N. Gokul, 2022

Gokul, Gopinathan Nair & Thomas, Jacob, 2022, A New Species of Black Mildew Causing Fungus Meliola konniensis (Meliolales) from Agasthyamalai Biosphere Reserve, India, Phytotaxa 545 (2), pp. 224-228 : 227

Meliola konniensis Jacob Thomas & G. N. Gokul sp. nov. ( Figs 1 , 2 ) MycoBank No.: MB 839626

Type:— INDIA, Kerala: Pathanamthitta, Konni forest division, Manneera , on the living leaves of Aglaia perviridis Hiern (Meliaceae) , 29 December 2018, Gokul & Jacob Thomas, MTCHT 231 (holotype) ; CATH 18004 (isotype) .

Colonies epiphyllous, very thin, scattered, up to 2 mm in diameter. Hyphae straight to substraight, branching opposite at acute angles, loosely reticulate, cells 11–28 × 4–7 μm (x̅ = 20.12 × 5.93 μm, n = 50). Appressoria opposite, rarely alternate, antrorse, 13–17 μm (x̅ = 14.61, n = 50) long; stalk cells cylindrical to cuneate, 1.8–5.5 μm (x̅ = 2.95, n = 50) long; head cells ovate, entire, attenuated at the apex, 9–14 × 5–9 μm (x̅ = 11.80 × 6.92 μm, n = 50). Mycelial setae very few, arise from subiculum, simple, straight, acute to variously dentate at the tip, up to 260 (x̅ = 184.23 μm, n = 50) μm long. Sexual morph: Perithecia scattered, up to 150 μm (x̅ = 113.24 μm, n = 50) in diameter; ascospores oblong cylindrical, four-septate, slightly constricted at the septa, 30–37 × 10–16 μm (x̅ = 32 × 13.09 μm, n = 50). Asexual morph: Phialides mixed with appressoria, few, opposite, ampulliform, 13–22 × 4–8 μm (x̅ = 16.82 × 6.21 μm, n = 50).

Etymology:—Named after the study area.

Notes: — Zeng et al. (2017) listed the association of four species of Irenopsis , 10 species of Asteridiella and 57 Species of Meliola with members of Meliaceae . In the present collection the arrangement of appressoria are strictly opposite hence the characteristics of the specimen are compared with the most allied species reported on Meliaceae having opposite appressoria ( Table 1 ). In M. aphanamyxidis Hosag. , M. arkevermae Hosag. & Sabeena , M. dysoxyli Hansf. and M. reinwardtiodendri Hosag. appressoria and ascospores are larger in size and setae are longer with obtuse to acute apex. The present collection is comparable to M. thomasii Hansf. in dentate to bifid nature of setae but differs because of having significantly short setae and smaller size of perithecia and ascospores. In M. ekebergiae Hansf. appressoria are crowded and longer, hyphae are broader and setae are numerous with acute apex. Meliola amoorae Yates is having appressoria with cylindric head cells which are rounded at apex, setae are very long with acute at the tip and ascospores slightly smaller, ellipsoid in shape.

Eight species of Meliola so far reported infecting Aglaia are Meliola aglaiicola Hansf. , Meliola aglaiae Syd. (synonymised to Meliola parvula Syd. ), Meliola aglaina Hansf. , Meliola aglaiae-edulis Jana et al. , Meliola obvallata Syd. , Meliola sairandhriana Hosag. & Archana , Meliola savarkarii Hosag. et al. , and Meliola vazhachalensis Hosag. & Jacob Thomas ( Hansford 1961, Hosagoudar 1996, 2008, 2013, Hosagoudar & Sabeena 2014, Zeng et al. 2017). Among these M. aglaina reported from Philippines, M. sairandhriana and M. vazhachalensis reported from India are having strictly opposite appressoria ( Table 1 ). The specimen differs from M. vazhachalensis in having longer straight setae which is variously dentate at the apex, appressoria antrorse with apex of head cells attenuated and phialides strictly opposite in distribution. Mycelial setae of M. vazhachalensis are uncinate to slightly coiled and acute at the apex. In M. sairandhriana the size of perithecia and ascospores are larger, mycelial setae are longer, curved to uncinate at the apex and tip of the setae are obtuse to bifid. The head cells of the appressoria are clavate, mycelial setae are longer with acute apex and phialides develop opposite and alternate in M. aglaina (3112.3221). In the present collection mycelial setae are variously dentate, head cells of the appressoria are attenuated at the apex, phialides show opposite development only and the Beeli formula is 3132.3221. Hence the specimen is proposed as a new species.

Figures

FIGURE 1. Meliola konniensis. a. Surface mycelium. b. Appressoriate hypha. c. Hypha with phialides and appressoria. d. Hypha with ascoma initial and appressoria. e. Mycelial seta. f. Apex of mycelial setae. g. Mature ascospores. Illustration by G.N. Gokul.

FIGURE 2. Meliola konniensis. a. Infected leaves. b. Surface mycelium and mature perithecia. c. Appressoriate hypha. d. Hypha with phialides and appressoria. e. Mycelial seta. f. Apex of mycelial setae. g. Mature germinating ascospores. Photographs by G.N. Gokul.