Fisiologia, componentes do monociclo da podridão de Neonectria ditissima em frutos e sobrevivência de patógenos em ramos de macieira

The southern region of Brazil stands out in the production of apples (Malus domestica). In 2012, the Ministry of Agriculture, Livestock and Supply (MAPA) confirmed cases of European Canker (Neonectria ditissima, anamorph Cylindrocarpon heteronema) in the states of Rio Grande do Sul and Santa Catarina, and in Paraná were reported only in the region of Palmas. The lack of information about the behavior of the pathogen under Brazilian conditions, especially with regard to infection in fruits, compromises the control of the disease in the field. In addition, there is no literature on the survival of this and other pathogens in apple tree twigs in dormancy and bud break in production areas. Therefore, this work was divided into two chapters. In the first chapter, we studied the effects of different temperatures and wetness periods on physiological processes of the imperfect stage of Neonectria ditissima in vitro, as well as infection, colonization and reproduction in fruits. The pathogen presented potential of germination, mycelial growth and sporulation in a wide temperature range. For the germination the best temperature tested was 20 °C, and wetness periods of more than 12 hours were sufficient for the germination of 70% of the conidia in the temperature range between 10 and 30 °C. The optimum estimated temperature for the mycelial growth of the isolates varied between 16,6 and 18,42 °C. Production of microconidia was higher at 20 °C, whereas for the production of macroconidia the temperatures of 15 and 20 °C were better. Isolates collected at different times and/or places did not present differences in the aggressiveness on ‘Gala’ apple fruits. Although the presence of N. ditissima is not yet detected in Campo Largo and Porto Amazonas, the climatic conditions of these regions are as favorable as those in regions of Rio Grande do Sul in which the disease in fruits has already been observed. The cultivar Eva does not differ from the cultivar Gala in relation to the susceptibility to fruit rot by N. ditissima. The second chapter evaluated the presence and survival of pathogens in apple tree twigs as inoculum potential on bud break. Several pathogenic fungi genera were detected: Neonectria ditissima, Colletotrichum sp. , Botryosphaeria sp. , Alternaria sp. , Fusarium sp. Aspergillus sp. , Penicillium sp. and Rhizopus sp. Winter treatments were efficient for reducing the inoculum of the genera Colletorichum, Aspergillus, Penicillium and Rhizopus. It was observed a high incidence of the genera Botryosphaeria, Alternaria and Fusarium in the sprouting period that can become a phytosanitary problem if specific control measures are not directed to the reduction of the primary inoculum. N. ditissima was detected in the Palmas PR areas, even after winter treatments, being a potential source of inoculum for infection during sprouting. The pathogens N. ditissima, Colletotrichum sp. , Botryosphaeria sp. , Alternaria sp. and Fusarium sp. isolated from apple tree twigs were pathogenic to ‘Gala’ apple fruits. Specific control measures for primary inoculum reduction should be studied to minimize the impact of field epidemics. Key-words: Neonectria ditissima; Malus domestica; monocycle; disease; survival; twigs.