The effect of cultivation conditions on growth, sporulation and formation of morphological structures of Topospora myrtilli (Feltg.) boerema

Abstract

The growth of Topospora myrtilli isolates, obtained in the years 2001-2003, was studied on PDA medium at -10, +2, +6, +12, +18, +22 and +28°C. The growth and sporulation of the isolates were observed at +22°C on the following culture media: PDA, maltose - MA and mineral - MSA, as well as on two versions of oat media, one containing 20 g of oat flakes per litre (OA-20), and the other containing 50 g of oat flakes per litre (OA-50). The observations of the linear growth of colonies of the studied strains were carried out during a period of 21 days, whereas the formation of morphological structures until the 52^nd day of cultivation. It was found that T. myrtilli can grow and sporulate in a wide range of temperature, even at +2°C. The pathogen growth activates with the increase of temperature, up to the optimal temperature, i.e. from +18°C to +22°C. The increase of temperature to +28°C did not favour the mycelium growth and prevents pathogen sporulation. PDA, OA-20, OA- 50 and MA media can be considered to be the most suitable for the growth and development of T. myrtilli, due to the intensive growth and formation of typical macro- and microscopic features. It is necessary to emphasise the great usefulness of oat medium, especially OA-50, for the cultivation of Topospora myrtilli, in the aspect of sporulation of the fungus. It was found that mineral medium is unsuitable due to the formation of mycelium with an untypical structure and colouration as well as late conidial sporulation.