Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

In vitro effects of temperature and wet periods on infection of oilseed rape by Alternaria brassicae.

Abstract

The influence of temp. and duration of wet periods on infection of rape by A. brassicae was studied on detached leaves and pods, leaf discs and intact seedlings. Infections increased with age of leaf and the interaction between temp. and leaf age was highly significant (P<0.001). On older leaves infection was opt. at 25°C. There were also many infections at 15, 20 and 29° but relatively few infections at 10°. On pods most infections were observed at 20°, the highest temp. studied. Infection at each temp. increased progressively with duration of surface wetness. The min. wet periods for infection of leaves were 3 h at 20-25°, 4 h at 15°, 6-9 h at 10° and 12-24 h at 5° and for infection of pods, between 6 h and 9 h at 10° and 6 h (or less) at 15° and 20°. On leaves, dry periods interrupting wet periods limited lesion development to that obtained with the initial wet period only; on pods some further infections developed when pods were re-wetted. Dry periods of 3 h and 6 h following the inoculation of pods reduced subsequent infection but there was no further reduction by longer periods of drying to 48 h.