ABSTRACT
Three streptomyces isolates causing potato common scab disease [i.e., S1, S2 and S3] were successfully isolated and identified from the growing areas at Menia. Pathogenicity tests, either in the laboratory or pots, revealed that potato cultivars Alpha, Diamont and Spunta could be infected by all three S. scabies isolates. The tested isolates caused lesions on the root tips of radish, software, soybean, squash, tomato, turnip and wheat seedlings. Only isolate S2 induced lesion on the root tips of cowpea, Nicotiana glutinosa, and sunflower seedlings. None of the S. scabies isolates infected maize seedlings or storage roots of carrot and sweet potato. However, storage roots of radish were infected by the highly pathogenic isolate S2. S. Scabies isolates produced phytotoxic substances with most produced after five days at 25C