Infection of grapevines by different propagules of the black foot pathogens, Ilyonectria/Dactylonectria spp., in soil

Abstract

Black foot disease is a major disease of grapevines worldwide, causing the decline and eventual death of young vines. The causal agents are reported to be soilborne pathogens from several genera including Cylindrocarpon, Dactylonectria and Ilyonectria (1). A survey of symptomatic vines in New Zealand identified Ilyonectria liriodendri, Dactylonectria macrodidyma and species within the I. radicicola – complex as being the main species associated with the black foot disease complex (2,3,4). These pathogens are reported to infect grapevines from soil borne inoculum produced on infected belowground host tissue, which can remain in soil after removal of infected plants, or spread through movement of soil and water (5). Most Dactylonectria and Ilyonectria species produce conidia and chlamydospores, however the relative pathogenicity of the propagules including mycelium has not been well studied. Further, black foot disease has also been reported to develop preferentially in poorly drained heavy soils (6). This study aimed to determine the relative pathogenicity of the different Ilyonectria/Dactylonectria species propagules in soil, and whether soil type influences infection of grapevine cuttings by these propagules.