DNA isolated from Fusarium lateritium Nees: Fr.-infected `Jewel' sweetpotato [Ipomoea batatas (L.) Lam.] plants was compared to F. lateritium-free `Jewel' plants for differences in random amplified polymorphic DNA (RAPD) marker products. Differences in RAPD marker products were detected. Amplified DNA isolations from F. lateritium-infected `Jewel' plants generated additional, unique DNA fragments not found in amplified DNA isolations of F. lateritium-free `Jewel' plants. These unique amplified DNA fragments were consistent with those obtained from amplified DNA isolations of the F. lateritium isolate, 91-27-2, used for inoculation. We found that F. lateritium DNA successfully competes with sweetpotato DNA in the polymerase chain reaction for priming sites in a 3: 1 ratio of sweetpotato DNA to F. lateritium DNA. Our results indicate the importance of avoiding plant material infested with pathogens to avoid spurious marker bands.
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