In vitro effect of the crude extract of a potato common scab streptomycete in Sinaloa, Mexico

A strain isolated from potato common scab superficial lesions in El Fuerte Valley in northern Sinaloa, Mexico, was identified by 16S rRNA and morphological methods. Moreover, the effects of the crude extract of strain V2 was evaluated on radish and potato. The isolate was similar to Streptomyces acidiscabies in its morphological properties; however, the 16S rRNA gene sequence of strain V2 was neither 100% identical to this species nor to the streptomycetes previously reported in Sinaloa, Mexico. Strain V2 did not amplify any specific PCR products for genes nec1 and tomA, which have been found and reported in S. acidiscabies. Strain V2 produced a PCR product for the txtAB operon, which is related to the production of thaxtomin. In vitro assays using crude thaxtomin extract and a spore suspension of the organism caused necrotic symptoms on radish and potato, which were highly virulent in potato. This study reports that Streptomyces sp. V2 has a toxigenic region (TR) that is associated with the thaxtomin gene cluster.