Disease severity and diversity among Actimycests isolated from diseased potato

Actinomycests are soil habitant which among them Streptomyces are plant pathogens. They were isolated from potato scab lesion complex collected from crop growing area. Pathogenicity on mini-tuber and plants were done and they were tested for: the presence of nec1 gene, diversity and differences in disease severity induction. Results indicated that most of the strains harbor nec1 and they were belong to five groups similar to S. scabies, S. acidiscabies, S. turgidiscabies, S. caviscabies and Streptomyces sp. Severity disease induction trial showed significant differences with scale ranged from zero to 10 . They induced raised or pitted lesion in three levels: strong, mild and weak. Diversity and disease severity spectrum could be due to introduction of mother potato tuber from different area and courtiers. Continuing of this strategy result emergence of new pathogenic strains as pathogenicity genes reside on a large mobile pathogenicty island in some potato pathogenic Streptomyces spp. Keywords— nec1, Pathogenicity island, Raised symptoms, Streptomyces