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Description type:Original description 
Description:PERENNIPORIA PHLOIOPHILA Gilbn. et M. Blackwell, sp. nov.
Typus: on Quercus virginiana Mill., Louisiana State Univ., Baton Rouge, East Baton Rouge Parish, LA, R. L. Gilbertson 13308, Aug. 27, 1981 (BPI) .
Basidiocarps resupinate to slightly reflexed, perennial, developing as small single units 0.7-6 cm wide or becoming confluent and up to 1 meter in largest dimension, conforming to the topography of the bark; pore surface cream-colored to pale buff, the pores circular to angular, 3-5 per mm; dissepiments thick, entire; context white to cream colored, less than 1 mm thick; tube layer indistinctly stratified, up to 2 mm thick, older layers often stuffed with white mycelium.
Hyphal system trimitic; generative hyphae (Fig. 3a) 2-4 µm in diam, inconspicuous and difficult to discern, thin-walled, with clamps; binding hyphae (Fig. 3b) 2-4 µm in diam, thick-walled, nonseptate, with frequent branching, negative in Melzer's reagent; skeletal hyphae (Fig. 3c) mostly 2.5-5.5 µm in diam but some slender skeletals 1-2 µm in diam also present, thick-walled, with occasional branching, nonseptate, dextrinoid in Melzer's reagent; cystidioles (Fig. 3e) 16-20 x 6-8 µm, fusoid, thin-walled, not projecting basidia (Fig. 3d) 16-28 x 8.5-11 µm, broadly clavate, 4-sterigmate, with a basal clamp; basidiospores (Fig. 3f) 7.5-11 x 6-8 µm, ellipsoid, smooth, thick-walled, with a thin-walled truncate apex, hyaline in KOH, dextrinoid in Melzer's reagent.
Perenniporia phloiophila is perhaps most similar to P. medullapanis (Fr.) Donk, a widely distributed species on dead hardwoods throughout the temperate regions of the world. However, P. phloiophila is morphologically distinct because of its larger basidiospores (7.5-11 x 6-8 µm as compared to 5-7 x 3-5 µm for P. medulla-panis) and specific habit and host relationship. Furthermore, it is genetically isolated from P. medulla-panis with homokaryons from the two species completely incompatible. Perenniporia fraxinophila (Pk.) Ryv. has basidiospores
more like those of P. phloiophila but differs in producing large pileate basidiocarps and occurring mainly on ash. Perenniporia fraxinophila is also genetically isolated from P. phloiophila.
Perenniporia phloiophila commonly fruits profusely on bark of large living branches and main stems of trees that show no dieback or other symptoms of deterioration. Sections of branches infected with P. phloiophila show that mycelium is usually restricted to the dead, nonconducting outer bark. However, in one instance, damage of bark by insects and birds apparently resulted in invasion of underlying wood by the fungus, and subsequent develoµment of a uniform white rot. Isolates of P. phloiophila from bark and decayed wood of this collection were identical with isolates obtained from mass basidiospores.
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