Acquired resistance of Alternaria solani and Sclerotium rolfsii to polyoxin-D.

Acquired resistance to the antibiotic polyoxin-D was studied in two phytopathogenic fungi, Alternaria solani Sorauer, and Sclerotium rolfsii Sacc. The ED50 value of the antibiotic for A. solani was 100 ftg/ml and S. rolfsii 200 fig/ml. A. solani and S. rolfsii could be trained to tolerate concentrations up to 1.000 (Ag/ml and 2.200 Hg/ml respectively. The acquired resistance in both cases was not lost on continued subculturing in fungicide-free media. On transfer to fungicide-free media, Polyoxin-resistant strains of both the fungi showed faster growth rate and appreciable reduction in sporulation compared to the original strains. The adapted strain of A. solani showed cross-resistance to Cycloheximide and Difolatan but not to Hinosan and Bayleton. [ABSTRACT FROM AUTHOR]