Molecular characterization and genetic relatedness among walnut (Juglans regia L.) genotypes based on RAPD markers

The potential use of the Randomly Amplified Polymorphic DNA (RAPD) technique for characterization and assessment of genetic relationships was investigated in nineteen walnut (Juglans regia L.) genotypes used as parents or released as cultivars from the breeding program of the University of California at Davis. Most of the 72 decamer primers used yielded scorable amplification patterns based on discernable bands. The results obtained produced a unique fingerprint for each of the walnut genotypes studied. Cluster analysis separated the 19 walnut genotypes into two main groups whose differences were related to their pedigree. Genotypes sharing common parents tend to group together and with at least one of the parents. Thus, RAPD markers can detect enough polymorphism to differentiate among walnut genotypes, even among closely related genotypes, and the genetic similarity based on RAPDs appears to reflect the known pedigree information. RAPD technology can be useful in current walnut breeding programs, allowing the identification of new cultivars as well as the assessment of the genetic similarity among genotypes which will help in selecting the best parents to obtain new genetic combinations. This revised version was published online in July 2006 with corrections to the Cover Date.