Identification and Characterization of Actinomycetes for Biological Control of Bacterial Scab of Streptomyces scabies Isolated from Potato

Abstract

A novel strain of Streptomyces in Egypt (known asStreptomyces scabies) was isolated from a scabby potato field in different regions of Egypt. The taxonomy of the organism was determined by morphology, biochemistry, and  physiological characteristics. Two bacterial strains (actinomycetes) which were  isolated from soil sample and showed antagonistic activity towards potato scab were identified using specific polymerase chain reaction (PCR) of 16S rDNA gene. The 16SrDNA sequence analysis showed that  the 1^st strain belongs to the genus Streptomyces, with closest similarity to Streptomyces avermitilis MA-4680 (100% similarity). Sequence similarities between the 1^st strain  and other Streptomyces species in the same subclade ranged from 98% (with Streptomyces griseus NBRC 13350 and Streptomyces sp. Wigar10). Keyphenotypic characteristics as well as chemotaxonomic features of the actinomyces were congruent with thedescription of the genus Streptomyces. On the basis of phenotypic and phylogenetic analyses. The 2^nd strain identified as Actinomyces odontolyticus ATCC 17982(100% similarity). Sequence similarities between the 2^nd strain  and other Actenomycetes species was 98% (with Actinomyces odontolyticusC 505).

The two identified strains showed a high level of antibiosis against pathogenic organism (Streptomyces scabies) and achieve a significant control of disease as no sign of disease symptoms are shown on the tested varieties of potato ( Cara and Diamond)

Keywords: Actinomycetes, biological control, Streptomyces scabies.