Patogenicidade e transmissão de fungos associados às sementes de teca e progresso temporal da ferrugem causada por Olivea Neotectonae

Abstract

Teak (Tectona grandis L.f.) is an arboreal species widely used in reforestation areas and is the third species among the most planted tropical hardwoods in the world. Throughout their vegetative cycle, teak can be affected by a large number of diseases having in fungi the main phytopathogenic agents. Among the diseases that occur in culture, rust caused by Olivea neotectonae T.S. Ramakr. & K. Ramakr (=Chaconia tectonae T.S. & K. Ramark), stands out as the most important. The production of teak seedlings is mainly through seeds, which is an important vehicle for transmission of various pathogens. Due to the scarcity of information related to health of teak seeds used in Brazil for its cultivation, the aim of chapter I was to identify and quantify the fungi associated with teak seeds, the pathogenicity of these microorganisms to seedlings and seed-seedling transmissibility. For sanity test were utilized seeds acquired in TO, GO and SP states, the treatments were disinfested seeds and without disinfestation and seeds with and without mesocarp. We conducted the test using a filter paper method (Blotter test). To pathogenicity test in seedlings, we utilized the isolates of Fusarium sp., Botryodiplodia sp., Alternaria sp. and Plenodomus sp. To evaluate the fungal seedling-transmission were used 100 seeds of each location. Overall, it was possible to identify the following genera of fungi in seeds: Fusarium, Trichoderma, Botryodiplodia, Aspergillus, Penicillium, Rhizopus, Cladosporium, Alternaria and Plenodomus. There was a higher occurrence of fungi in the seeds of Goiás and São Paulo states. Only the Fusarium sp. and Botryodiplodia sp. were pathogenic to teak seedlings. There was low seed-seedling transmissibility, and only the pathogenic genera Fusarium sp. and Alternaria sp. were transmitted. In chapter II, was performed an epidemiological study of teak rust with the analysis of the temporal dynamics of disease in adult trees, correlating the disease behavior of climate variables, to understand the epidemic's behavior and thus establish alternatives to appropriate management. The disease was monitored every seven days at ten plants randomly chosen to evaluate the incidence and severity, this being quantified with assistance of a grade scale. With these data were obtained the disease progress curves by adjusting the mathematical models monomolecular, logistic and Gompertz. The area under the disease progress curve (AACPD) was calculated for incidence and severity. The incidence and severity data was correlated with the climatic variables, precipitation, temperature and medium relative humidity. The rust incidence was verified from the earliest evaluations, exponentially increasing until 98 days of evaluation. Higher index of severity was detected with 147 days, with a severity greater or equal to 75%. A higher AACPD was observed for the incidence. There was a negative and significant correlation between the severity with the minimum temperature. It is inferred, with this result, a tendency of increasing of severity of teak rust with the decreasing of temperature in the evaluated conditions. The Gompertz model was the best adjusted to the data severity of the teak rust.