DIVERSITY WITHIN STREPTOMYCES-IPOMOEAE BASED AN INHIBITORY INTERACTIONS, REP-PCR, AND PLASMID PROFILES

Streptomyces soil rot is a destructive disease of sweetpotato (Ipomoea batatas) that causes yield loss resulting from decay of the feeder ro ot system and reduced quality due to the presence of necrotic lesions on the storage roots. it is managed by the use of resistant cultivars, but variability of the pathogen has not been previously assessed. Thi s study compared 36 strains of the pathogen Streptomyces ipomoeae from different locations in the United States and Japan. The strains could be separated into three groups on the basis of their ability to inhib it the growth of one another in in vitro assays. Although some strains contained plasmids of approximately 18, 42, or 270 kb in size, plasmi d profiles did not correspond to inhibition grouping. Fingerprinting b y repetitive element-based polymerase chain reaction (rep-PCR) using o utwardly facing primers for the BOX, enterobacterial repetitive interg enic consensus (ERIC), and repetitive extragenic palindromic (REP) seq uences indicated relatively high genomic homogeneity within S. ipomoea e. However, cluster analysis of similarity coefficients among strains using rep-PCR data revealed clusters that correlated with the inhibiti on grouping. The neotype strain of S. ipomoeae had lower similarity va lues by rep-PCR than any of the other strains and could not be grouped by inhibitory interactions.