Response of Alternaria alternata and A. brassicicola to sulphur dioxide in vitro

Abstract: Sulphur dioxide at 100 (except 3 h for Alternaria alternata) and 200 ug m? suppressed the radial growth ofA.alternataand A. brassicicola, the growth being lowest at 200 ug m? for 12 h. The sporulation of A. brassicicola wassignificantly enhanced at 100 ug S02 rrr', but inhibited at 200 ug m? (6-12 h). Sporulation of A. alternata was significantlygreater at 100 1!g S02 m? (3-6 h) and at rest of the doses it was inhibited. S02 at 100 ug rn? significantly stimulated spore germination of A. alternata (3-9 h) and A. brassicicola (3-6 h). At rest of the treatments, the germinationwas suppressed. Length of spores and number of cells/spore were increased as a result of exposure to 100 ug S02 rn", while remained uninfluenced at 200 ug. Septation (tranverse and longitudinal) of spores of the Alternariaspecies also showed varied response