TOXIGENIC POTENTIAL OF ALTERNARIA-MACROSPORA PATHOGENIC TO COTTON

Alternaria macrospora Zimm. causing leaf spots on cotton, was grown on three culture media viz. Czapek-Dox liquid medium (CD), CD with 0.5% peptone and CD with 0.5% yeast extract for testing its toxigenic poten tial. The culture filtrates of the pathogen exhibited phytotoxicity ag ainst cotton (host), tomato and bajra (non-hosts) as well as antibacte rial activity. The culture filtrates collected from CD with 0.5% pepto ne were more toxic to the test plants than the other two. The toxic ef fects of culture filtrates gradually increased with aging of the cultu res in the three cases. Analysis of the crude toxin revealed the prese nce of two phytotoxic compounds, of which one was identified as tenuaz onic acid.