Levantamento de doenças foliares de natureza fúngica em áreas de plantio de Acacia mangium e Eucalyptus urograndis no município de Itacoatiara - AM.

Abstract

Acacia mangium and Eucalyptus urograndis, Mimosaceae and Mirtaceae families, respectively, are exotic, natural forest species from Australia. These tree species stand out for their high wood potential and silvicultural versatility, and have been used as energy sources in the ceramic industries in the Amazon. A. mangium is reported as a multipurpose species, also used in the recuperation of degraded areas. In order to characterize parasitic fungi in these forest species, a survey was carried out in 2017 in forest plantations owned by Litiara Indústria Cerâmica da Amazônia Ltda, located at Km 19 of Highway AM-010 (direction ITA-MAO), in the municipality of Itacoatiara. Were are isolated and identified the fungi Cylindrocladium sp., Colletotrichum sp., Phomopsis sp., Macrophoma sp. and Pestalotia sp., associated with distinct leaf spots in the acacia mangio species, and two unidentified fungi in the eucalyptus species. A total of 15 isolates of A. mangium and 01 isolates of E. urograndis were used for assesment of the growth rate (TCMD), using colonies purified from tissue fragments presenting typical symptoms of disease. Among the isolates of A. mangium, the highest TCMD was observed for isolate 2027A (A12, Col. 1.1). Among the fungi identified and tested for pathogenicity, the 03 isolates of Pestalotia sp. together with Macrophoma sp., presented the highest growth rates (above 5.48 cm on day 6). Cylindrocladium sp., the only isolate with positive reaction in pathogenicity tests, had the lowest growth rate (5.34 cm on day 6). Pathogenicity tests were carried out on detached and healthy leaves from the terminal branches of the acacia mangio and eucalyptus species, from the colonies stored in glass flask by the Castellani method. The test was carried out in plastic trays in the laboratory, depositing 5 mm diameter BDA (Potato-Dextrose-Agar) discs, with and without the fungus, on the abaxial and adaxial faces of the leaves, previously scarified with a histological needle and in intact leaves. The leaves were kept in a humid chamber for 48h. Four days after inoculation, symptoms similar to leaf spot with and without scarification were observed, only for 03 isolates of Cylindrocladium sp. For the other fungi, no typical symptoms were observed on leaves of acacia mangio and eucalyptus. The fungus Cylindrocladium sp. was reisolated of the spots and again cultivated in BDA, completing the Koch Postulates. This is the first report of the occurrence of leaf spot caused by Cylindrocladium sp., in A. mangium in Brazil.