Temperature and light intensity interaction on Cercospora coffeicola sporulation and conidia germination

Interação da temperatura e intensidade luminosa na esporulação e germinação de conídios de Cercopora coffeicola

ABSTRACT

Difficulty in obtaining abundant sporulation in culture of many species of Cercospora may be the limiting factor for studies of biology, systematics, and inoculation of the genus. Therefore, it is necessary to understand the nutritional and environmental requirements that influence mycelial growth, sporulation and germination. As it is difficult to obtain conidia of Cercospora coffeicola in vitro, different temperatures (17, 22, 27, and 32 °C) and light intensities (80, 160, 240, and 320 μmol m^-2 s^-1) were evaluated to optimize pathogen sporulation and assess favorable conditions for spore germination, aiming for a strategy of disease control. The dark treatment (0 μmol m^-2 s^-1) was added for sporulation. A significant interaction was found between temperature and light intensity for both variables. The highest sporulation rate of C. coffeicola occurred at a light intensity of 240 μmol m^-2 s^-1 and air temperature of 22 °C, reaching 5.9x10⁶ con mL^-1. Germination was higher at temperature 17 °C and light intensity of 320 μmol m^-2 s^-1, reaching 52%. Interaction between light intensity and temperature proved to influence the processes of sporulation and germination of C. coffeicola.

Index terms:
Environmental variables; Cercospora leaf spot; Coffea arabica