Effects of solar radiation and relative humidity on germination of Botryosphaeriaceae species conidia

Abstract

Viability and germination of conidia of three Botryosphaeriaceae species, which are important grapevine pathogens, were significantly affected by exposure to different levels of sunlight and relative humidity (RH). After 7 h exposure to non-filtered sunlight (+UV), filtered sunlight (-UV) and shade, germination differed between light levels, being 35, 57 and 81%, respectively, and after 70 h exposure it was 0, 21 and 65%, respectively. Non-germinated conidia were unable to germinate when placed in a moist environment, indicating that they had been killed. High RH favoured germination since 91 and 70%, respectively, germinated after 3 h in 100 and 97% RH. However, in 93% RH, only 44% germinated by 24 h and in 84% RH no conidia germinated. The inhibition of germination was temporary since replacement in a moist environment caused conidia to germinate. Light and RH effects were similar for the three species.