Colonization of wheat seedling leaves by Fusarium species as observed in growth chambers: a role as inoculum for head blight infection?

Abstract

Fusarium species involved in the Fusarium head blight complex in Western Europe were investigated for their potential to infect and colonize non-damaged wheat leaves and to produce conidia on senescing wheat leaves incubated at high relative humidity. Fusarium avenaceum, Fusarium culmorum, Fusarium graminearum, Fusarium poae and Fusarium tricinctum did not directly penetrate the leaf tissue after conidia germination on the leaf surface. Germ tubes grew on the host surface for 24–36 hr forming a mycelial network. After invading the host, some species formed runner hyphae between cell wall layers or underneath the cuticular layer. Macroscopic symptoms developed on leaves and stems from 7 d post inoculation. Inside leaf tissues, hyphae thickened in diameter and were both inter- and intra-cellular. Fusarium tricinctum formed sporophores which erupted through the leaf surface releasing numerous conidia. Incubation of senescing leaves at 100 % relative humidity for 48 hr resulted in sporulation of all Fusarium spp.