RESUMO
Leaves, young branches, and fruits of Acacia farnesiana (L.) Willd. (Fabaceae) that were distorted because of hypertrophy causing witches' brooms and other abnormal growth were collected in the area surrounding the Panteón da Liberdade e da Democracia, Brasilia, Brazil, during August 2005. Uredinia and telia were observed in the symptomatic areas. The uredinia were small on leaflets and rachis and on pods in confluent groups as much as 1 cm in diameter, subcuticular becoming erumpent, and cinnamon-brown; paraphyses were mostly clavate and colorless. Urediniospores were 17 to 28 × 12 to 16 µm, ellipsoid to obovoid, with a wall 1.5 to 2 µm thick at the sides and 2 to 3 µm at the apex, cinnamon-brown, with hub and spoke pattern of ornamentation, and pores in two bands of four each above and below the equator. Telia were small, erumpent, on rachis and small branches, and dark cinnamon-brown. Teliospores were 84 to 100 × 65 to 90 µm in diameter, chestnut-brown, (4) 5 to 6 probasidial cells across, and smooth; cysts were globoid, same number as peripheral probasidial cells; pedicels were colorless, multihyphal, and deciduous. The rust was identified as Ravenelia spegazziniana J.C. Lindq, on the basis of the comparison with specimens deposited at the Instituto Spegazzini (LPS) and U.S. National Fungus Collection (BPI), as well as with published descriptions (2). R. spegazziniana has been reported on species of Acacia from Central, North, and South America, and Hawaii (1). A. farnesiana is probably native to tropical America, but it is naturalized and cultivated all over the world where it has become invasive in disturbed areas in some Pacific islands. This species is economically important for fuel wood, flowers used in the perfume industry, and bark and fruits used for tannin production. In Federal District (DF), Brasilia, Brazil, A. farnesiana is commonly used in urban forestation as an ornamental and shade tree. To our knowledge, this is the first report of R. spegazziniana in Brazil. The voucher specimen has been deposited in the herbarium of the Faculty of Biology of Porto Alegre from the Universidade Federal do Rio Grande do Sul as ICN 139085. References: (1) D. F. Farr et al. Fungal Databases. Systematic Botany and Mycology Laboratory. On-line publication. ARS, USDA, 2006. (2) J. R. Hernandez and J. F. Hennen. Mycol. Res. 106:972. 2002.
