Proliferobasidium heliconiae
Proliferobasidium heliconiae J.L. Cunn. 1976, in Cunningham, et al., Mycologia, 68(3), 640-654 (1976).
Diagnosis: Infection originally appearing on lower surface of the leaf, causing broadly elliptic brown spots with erumpent, pale yellow to brown fungus fruiting masses formed as minute, central, discrete, flattened pustules, which later become confluent; brown spots developing also on the upper surface of the leaf, without fungus fruiting masses; injury restricted to infected spots and adjacent regions of affected leaves. Fungus developing in the spongy parenchyma of the host as intercellular hyphae, erumpent from a small subepidermal stroma through the epidermis and stomata of the lower leaf surface as sorus-like masses of hyphal tips, forming thin, discrete, then coalescent fruiting masses which are gelatinous-waxy when moist, drying waxy. Hyphae colorless or pale yellow, thin-walled or moderately thin-walled, branched, septate, without clamp connections, 2 pm broad. Basidia originating by transformation of hyphal tips to form persistent probasidia which are pale yellow, narrowly clavate, and thick-walled when well-developed, attaining a size of (20-)34--68(-1,320) X 5-6 µm, erupting apically to produce a metabasidium; metabasidia cylindrical or filiform, thin-walled, up to 40-60 X 4-5 µm, terminally divaricate and forming two stout, apically truncate sterigmata 4-8 X 2-4 µm, from which spicula develop at maturity; metabasidium and sterigmata collapsing after spore production and remaining as a frayed vestige at the probasidial apex, with successive basidia regenerating by internal proliferation from the base of the persistent probasidial wall and erupting apically or occasionally laterally. Basidiaspores colorless, smooth, thin-walled, ellipsoid to allantoid-ellipsoid, non-septate, or becoming septate on germination, (10-) 12-20( -26) X ( 3-) 4-5 ( -6) µm, often produced successively in several pairs, commonly adhering laterally in one or several pairs when discharged, germinating by formation of germ tubes or blastospores ; blastospores colorless, smooth, thin-walled, globose, one celled, 3.5-4.5 µm diam.
Index Fungorum Number: IF321003
Figures 1-5. Proliferobasidium heliconiae. 1. Lesion on lower surface of a leaf of Heliconia bihai, X 5.5. 2. Metabasidium with sterigmata, erumpent from thick-walled probasidium, X 600. 3. Blastospore formation, X 440. 4. Percurrent proliferation of new basidia from within persistent probasidial walls, X 600. 5. Group of older basidial remnants, X 600.
Figures 6-9. Proliferobasidium heliconiae, X 1,000. 6. Basidiospores, showing septation and blastospore formation. 7. Germinating basidio~pores. 8. Stages of basidial development. 9. Basidial remnants after repeated episodes of proliferation.
Reference:
Cunningham, J. L., Bakshi, B. K., Lentz, P. L., & Gilliam, M. S. (1976). Two new genera of leaf-parasitic fungi (Basidiomycetidae: Brachybasidiaceae). Mycologia, 68(3), 640-654.
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