Streptomyces scabiei is largely accepted as
the causal organism of common scab on potato in
South Africa, and other Streptomyces species associated
with common scab are not often considered. This study
therefore aims to determine the diversity and prevalence
of Streptomycetes associated with common scab on potatoes
in South Africa. Isolates from 11 of the 16 potato
producing regions in South Africa were characterized
morphologically, physiologically and genetically.
Most isolates resembled S. scabiei based on
morphology and physiology. Most pathogenic isolates
were S. scabiei and S. stelliscabiei, and no
S. acidiscabies or S. turgidiscabies isolates were found.
All three pathogenicity/virulence genes (txtAB, nec1,
tomA) were found in South African isolates.
Pathogenicity could not be linked to the presence of a
single one or any combination of two of the three genes.
These results represent the most comprehensive published
survey of Streptomycetes isolated from common
scab lesions on potatoes in South Africa.