Merugia palicoureae Rogerson & Samuels
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Authority
Samuels, Gary J. & Rogerson, Clark T. 1990. New ascomycetes from the Guayana Highland. Mem. New York Bot. Gard. 64: 165-183.
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Family
Lasiosphaeriaceae
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Scientific Name
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Description
Species Description - Stroma superficiale, tenue, crustosum, nigrum, usque 1 mm diam., annulis concentricis. Perithecia centralia, ovoidis vel subglobosa, non papUlata, nigra, verrucosa, cuqusque 2-5. Asci cylindrici, 125-170 x 12-13 µm, apice annulo chitinoideo provisi. Ascosporae filiformes, 98- 120 X 3-4.5 Mm, 0-6-septatae, hyalinae. Pycnidia prope stromatis marginem immersa; cellulae conidiogenae iis Chalarae-similis, in hymenio basali productae; conidia clavatae, dacryoidae, vel oblongae, 6.2-7.4(-8.7) x 2.8-3 fim, unicellulariae, hyalinae. Stroma superficial, ca. 135 µm at thickest point in the middle, crustose, easily removed from the substrate, black, to 1 mm diam., with concentric rings; stromal surface ca. 20 fim wide, of dichotomously branched, short-celled, 5-7 µm wide, darkly pigmented hyphae; cells immediately below the surface angular, ca. 7.5 µm across, darkly pigmented, forming a region ca. 40 iim wide; stromal cortex ca. 75 µm wide at the widest
Distribution and Ecology - Guyana, known only from the type collection.
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Discussion
Habitat. O n stems and petioles of Palicourea sp.
Etymology of the Specific Epithet. Refers to the host plant.
TYPE. GUYANA: Mt. Wokomung, at base of exposed rock wall of main peak, 05°05'N, 59º50'W, elev. 1540-1570 m, on petioles and stems of Palicourea sp. (Boom 9211), 15 Jul 1989, Samuels (6552), Boom & Bacchus (holotype N Y , isotype BRG).
Notes. We have referred Merugia palicoureae to the Lasiosphaeriaceae because the ascal ring, which is inamyloid and chitinoid, resembles the apical ring of other members of that family (Lundqvist, 1972; Eriksson & Yue, 1989), and because of the persistent, apically free paraphyses, and long, colorless ascospores. The asci are freed from the hymenium and are presumably discharged intact; very few discharged ascospores were seen.
The anamorph, with conidia formed within collarettes of Chalara-like phialides, is not inconsistent with the Phialophora anamorphs attributed to some species of Lasiosphaeria (Gams & Holubova-Jechova, 1976). A n attempt to germinate ascospores of Merugia palicoureae on commeal dextrose agar at 20°C was unsuccessful. The intimate association ofthe pycnidia with the perithecia leaves no doubt that the two morphs are part of the same life-cycle. This anamorph cannot be identified to any ofthe genera included by Sutton (1980), but it can be accommodated in the anamorph order Phialidales suborder Phialostromatineae, as defined by Sutton (1980).
Stromata of Merugia palicoureae are not erumpent; they are easily removed from the substrate. There is no evidence of direct penetration of the apparently healthy tissues of the Palicourea. However, the dark porose cells that form in a single layer at the stromal base adjacent to the host tissue (Fig. 7) are reminiscent of appressoria formed by species of Colletotrichum (Sutton, 1980: fig. 320)