A study of Taphrina entomospora, leaf pathogen of Nothofagus

HANSEN P., BIANCHINOTTI M.V., RAJCHENBERG M.

MYCOLOGICAL RESEARCH

Elsevier

Año: 2007 vol. 111 p. 592 - 598

0953-7562

Background and Aims: Taphrina taxa are biotrophic fungi that produce infections and diverse symptoms on leaves, stems or fruits on a wide range of plants. Few Taphrina species have been described on native plants of the Southern Hemisphere, and these are still relatively unknown and poorly studied. Little is known about Taphrina entomospora, one of the few leaf pathogens known on Nothofagus pumilio. Our objectives were to study the anatomical changes that Taphrina entomospora produces in N. pumilio leaves, the host/parasite relationship and the morphology, cytology and cariology of the pathogen. Methods: For foliar anatomy and host/parasite relationship studies, sections of healthy and diseased leaves were dyed with safranine-fast green. For vegetative mycelium detection, sections were dyed with toluidine blue and orange G. Morphology of the pathogen was studied from free hand sections mounted in KOH 5% and dyed with Trypan blue. Caryological studies plus the ascogenous and ascospore developments of the fungus were done and followed with materials dyed with Heidenhain´s haematoxylin. Key results: The fungus is a perennial species, hibernating as mycelium in the foliar buds and infecting all the forming leaves from the beginning, for which reason the whole limb develops the disease symptoms. Leaves become chlorotic and thicker except the veins, with the intervenial limbs becoming roundish or as if blister-like. Histologically it was corroborated that the mycelium grows between the cuticle and the epidermis. The pathogen causes the palisade parenchyma to dissapear and the spongy parenchyma develops packed, roundish, isodiametric cells that leave little space between them. The pathogen’s mycelium growing in the abaxial side developed ascogenous hyphae; the latter divided transversely to form a dikaryotic ascogenous cell and a foot cell. After karyogamy, meiosis and a mitotic division, 8 nuclei were formed. Stages with 2, 4 and 8 nuclei were seen. Immature ascospores were ovoid to subglobose and hyaline but soon developed two apical buds and 2-4 lateral ones at each budding point; meanwhile the central cell was devoid of cytoplasm. The life cycle of T. entomospora is compared vis a vis other representative taxa in the genus and a discussion is presented regarding the distribution of this pathogen.