A new system of comparing PCR primers applied to ISSR fingerprinting of potato cultivars

Commercial scale fingerprinting of potato cultivars is made difficult by th e need for speed, reliability and the ability to distinguish between large numbers of genotypes. There are also problems in extrapolating the results of small experimental studies to predict the performance of techniques or p rimers for larger applications. The potential of ISSR-PCR for fingerprintin g purposes was evaluated using four primers on 34 potato cultivars. The com plex band profiles generated were reproducible between repeat PCRs, DNA ext ractions, electrophoreses and gel scorings. Two primers were each able to d istinguish all cultivars. The combined use of any two of the four primers a lso allowed complete diagnosis. It is concluded that ISSR-PCR provides a qu ick, reliable and highly informative system for DNA fingerprinting that is amenable for routine applications. Two possible correlates of the ability o f primers to distinguish between genotypes were then examined. Marker Index failed to correlate significantly with genotype diagnosis, but a strong an d seemingly linear relationship was observed between Resolving Power of a p rimer and its ability to distinguish genotypes (r(2) = 0.98). Resolving Pow er of one or a pair of primers was found to provide a moderately accurate e stimate of the number of genotypes identified. Possible implications for fu ture studies on DNA fingerprinting are discussed.