Caracterização morfológica, molecular e controle alternativo da ferrugem da teca (Olivea neotectonae) com óleos essenciais

Abstract

The area planted with teak (Tectona grandis L.f) has increased in Brazil and in recent years in the state of Tocantins. However, research related to phytosanitary problems of the species have not yet been developed, especially for the fungus Olivea neotectonae causal agent of rust teak, one of the fungal diseases of major economic importance in this forest species. Given this fact, the work was developed with the following objectives: In Chapter I, the morphological and molecular characterization of O. neotectonae, causal agent of teak rust was conducted. To this end, teak sheets featuring yellow and powdery pustules on the abaxial surface, characteristic of the teak rust were collected in the municipalities of Gurupi and Lagoa da Confusão in the state of Tocantins. In the observation by an optical microscope, they were viewed and measured fungal structures by scanning electron microscopy was observed pathogen structures and the penetration mode through the stomata. PCR amplification of the ITS region of rDNA O. neotectonae using pairs of primers ITS1-ITS4 was successful, obtaining a 600 bp fragment. Direct sequencing of the PCR product from ITS O. neotectonae region, suggested it is a species belonging to the family Chaconiaceae. Based on these results and of morphology observed was confirmed O. neotectonae as the causal agent of teak rust. In Chapter II, due to the absence of fungicides registered for the control of this disease in teak and the search for alternative methods of disease control that are not harmful to the environment, to evaluate the effect of the essential oils of lemongrass (Cymbopogon citratus L.), citronella (Cymbopogon nardus L.), mastruz (Chenopodium ambrosioides L.) and noni (Morinda citrifolia L.) on germination urediniospores O. neotectonae; assess the phytotoxic effect of these essential oils in teak seedlings; and evaluate the use of essential oils in control of the teak rust when applied preventive and curative manner. It was found that essential oils of noni and lemongrass inhibited 100% germination of urediniospores. However, when applied to plants at higher doses, the essential noni and lemongrass oils phytotoxicity caused plants. The majority chemical constituents were identified in the essential oil of lemongrass leaves the geranial (41.46%) and neral (32.43%), the grass citronella citronellal (30.07%) in matruz the α- terpineol (41.97%) and essential oil extracted from mature noni fruit was octanoic acid (64.03%). The preventive control was more effective in controlling the disease than curative application, both for lemongrass oil as for noni. When comparing the two oils in the curative control were found lower values of the Area Under the Rust Progress Curve when using the essential oil of lemongrass.