TOXICITY LEVEL OF SO_2 FUMIGATION ON SPORE GERMINATION OF ALTERNARIA ALTERNATA UNDER DRY AND WET CONDITIONS

摘要

Alternaria alternata, the leaf spot pathogen of sunflower was exposed under dry and wet conditions of different concentrations of SO, ranging from 10 to 500 ppm. Sulphur dioxide impaired the spore germination of the pathogen under both conditions. The adverse effect increased with the increasing pollutant concentrations. The spore germination of A alternata declined by 15.6% at 50 ppm, 30.3% at 100 ppm and 70% at 500 ppm concentration of SO_2 in dry conditions. Under the wet conditions of treatment as much as 95.5% spores were rendered non-viable at 500 ppm. Even 10 ppm of SO_2 impaired 12.3% spore germination. Keeping 50 ppm SO_2 concentration as constant, exposure inhibited 16.3 and 20.4% of spore germination under both the conditions, respectively. The inhibitory influence increased with increasing exposure periods. The exposure period of 6 h at this concentration inhibited 69.8% spore germination in dry condition, where as all the spore rendered non-viable at this exposure dose under wet condition.