Effects of temperature, pH and water potential on mycelial growth, sporulation and chlamydospore production in culture of <em>Cylindrocarpon</em> spp. associated with black foot of grapevines

Abstract

The effects of temperature, pH and water potential (Ψs) on mycelial growth, sporulation and chlamydospore production of Cylindrocarpon liriodendri, C. macrodidymum and C. pauciseptatum isolated from grapevines was studied. Three isolates per species were incubated on potato dextrose agar (PDA) under different temperature, pH, and Ψs conditions. All isolates were able to grow over a range of temperatures from 5 to 30ºC, with an optimum temperature between 20 to 25ºC, but they did not grow at 35ºC. Active mycelial growth was observed over a range of pHs, from 4 to 8. Regarding the effect of Ψs, in general, mycelial growth was greater on amended media at -0.5, -1.0 or/and -2.0 MPa compared with that obtained on nonamended PDA (-0.3 MPa), and was reduced at Ψs values lower than -2.0 MPa. Most of the Cylindrocarpon spp. isolates were sporulated at all temperatures, pHs and water potentials tested. In all studied conditions, C. liriodendri had the greatest sporulation capacity compared with C. macrodidymum and C. pauciseptatum. In general, chlamydospore production was not much affected by temperature, pH and Ψs. Chlamydospores were observed in PDA cultures of all isolates at all pH values studied, while some isolates did not produce chlamydospores at 5 and 10ºC or -4.0 and/or -5.0 MPa. These results improve understanding of the biology of these important grapevine pathogens.