Survival and seed to seedling transmission of Alternaria linicola on linseed

Abstract

Alternaria linicola survived as thick-walled chlamydospores in hyphal or conidial cells on infected linseed stem debris, either on the soil surface or buried in the soil, during the period between the harvest of linseed and sowing of the following crop (September - April). Conidia produced on these debris under favourable conditions were not only viable but also pathogenic to young linseed seedlings. Infected stem debris increased the incidence of infected seedlings which emerged from infected seed (incidence of A. linicola 1% to 28%), especially if the debris was on the soil surface rather than buried. A. linicola also survived between successive linseed crops on infected volunteer linseed plants which survived the low temperatures in winter and on the weed Veronica persica. A. linicola was more effectively transmitted from infected seeds to seedlings at temperatures 15-25 degrees C than at 10 degrees C. The incidence of the disease on seedlings which emerged from infected seed was positively correlated with the amount of seed-borne inoculum, whereas the proportion of seedlings which emerged was negatively correlated with the incidence of A. linicola on the seed.