Epidemiological survey on esca disease in Umbria, central Italy

Esca is a grapevine disease occurring in all vine-growing areas, including Italy. Multiple fungi that have been associated with esca spread by releasing aerial spores that infect pruning cuts and wounds. The aim of the study was to determine the occurrence of the most common fungi associated with esca in Umbria (central Italy) and to fi nd under what weather conditions they release their spores. Disease incidence was also determined in the summers of 2006 and 2007 on ten grapevine cultivars (Cabernet Sauvignon, Grechetto, Sangiovese, Trebbiano toscano, Pinot bianco, Trebbiano spoletino, Ciliegiolo, Montepulciano, Chardonnay and Merlot) growing together in the same vineyard. Visual inspection of the vines showed that all cultivars were susceptible to esca, but that esca incidence differed in intensity between cultivars. In both years, esca incidence was higher with Cabernet Sauvignon, Sangiovese and Trebbiano toscano, and lower with Montepulciano and Merlot. Disease incidence went up in summer. Phaeomoniella chlamydospora was isolated from vine samples showing dark wood streaking, and Fomitiporia mediterranea from samples with white rot, confi rming that these fungi are involved in esca. Spores of P. chlamydospora were trapped from March to December 2007. Spore release was affected by weather parameters (rain and temperature)

Histological, physiological and biochemical interactions between vesicular-arbuscular mycorrhizae and Thielaviopsis basicola in tobacco plants

Interactions between the mycorrhizal fungus Glomus monosporum and the root rot pathogen Thielaviopsis basicola and their effects on tobacco plants were investigated over a 4 week period. Mycorrhizal tobacco plants, obtained by preinoculation with G. monosporum, showed a better tolerance to T. basicola than non-mycorrhizal seedlings. Root and leaf dry weights of mycorrhizal plants were greater than those of controls. Mycorrhizal plants inoculated with T. basicola showed higher root and leaf dry weights than non-mycorrhizal infected plants, but lower values than mycorrhizal plants which were not infected. No appreciable differences in free aminoacid composition were observed among the different treatments with two exceptions: proline content was higher in infected and mycorrhizal infected plants compared to control and mycorrhizal plants; arginine content was higher in mycorrhizal plants than in all the other treatments