Alternaria brassicae in seeds of rapeseed and mustard, its location in seeds, transmission from seeds to seedlings and control.

Using the component plating technique, Alternaria brassicae was found predominantly in the seed coat and rarely in embryos of rapeseed (Brassica campestris L. var. toria) and mustard (Brassica juncea). The fungus sporulated profusely in the hilum region when tested by the deep-freeze blotter method. Field experiments conducted in 1991 and 1992 showed that the seed-borne inoculum of the fungus produced lesions on the cotyledonary leaves and then in first true leaves. In most cases A. brassicae sporulated within diseased tissues. The relationship between seed infection and disease transmission to seedlings was significant in the field trials of both years. Seed-borne inoculum of A. brassicae was controlled most effectively by sced treatment with iprodione (Rovral), thiram (Thiride), mancozeb (Dithane M-45) and captan also gave significant control. The paper discusses the implications of the survival of inoculum in stored seeds at low temperature and movement of infected seeds from gene banks to within a country or in other countries of the world.