Archivio Journal of Plant Pathology

Abstract:

Gymnosporangium sabinae (Dickson) G. Winter (syn. G. fus- cum DC.), the causal agent of European pear rust disease, can se- verely reduce yield of cultivated pear (Pyrus communis). This fun- gus, an obligate parasite that alternates between species of Junipe- rus and Pyrus to complete its lifecycle, is heteroecious and causes perennial infections on juniper and annual infections on pear (Laundon, 1975). In October 2011, leaves of cultivated pear trees of cv. Coscia, heavily attacked by a rust were collected in two or- chards located, respectively, in Baskinta [Mount Lebanon (33°56’39’’ N, 35°47’15’’ E)] and in Basloukite [north Lebanon (34°18’28’’ N, 35°58’02’’ E)]. Based on morphologic features (Parmelee, 1971; Laundon, 1975), the pathogen was identified as Gymnosporangium sabinae. On the upper side of the leaf, there were irregular, bright orange-red spots, which contained compact conglomerations of spermogonia. These structures were dark- brown to black, hemispherical, protuberant, 3-4 mm in diameter, had many receptive hyphae and produced at maturity a large number of oblong hyaline spores (spermatia) measuring 5.1- 7.2×1.2-1.8 μm. On the lower side of the leaf, there were loose conglomerations of horn-like aecia located on protruding tissue outgrowths. From these aecia, pale-brown pseudo-peridia arose as small groups of 2-4 mm-long filaments, composed of irregular- ly prolate peridial cells with inner and lateral walls extremely thickened, ornamented with cylindrical warts, which produced 24-30×23-28 μm subgloboid, ellipsoid aeciospores, with 4-5.5 mm thick orange-brown walls. Symptoms on surrounding Junipe- rus spp. were not observed. To our knowledge, this is the first re- port of G. sabinae on cultivated pear in Lebanon.