F.P. Nicese, J.I. Hormaza, G.H. Mc Granahan
Characterization of English walnut (Juglans regia L.) cultivars is of great importance, both for the evaluation of the effects of selection over time and for the development of crossing schemes in walnut improvement programs. The introduction of molecular biology techniques, such as DNA-based markers, has provided a new opportunity for genetic characterization, allowing the direct comparison of diverse genetic material without environmental influences on the results obtained. One of these techniques is the RAPD analysis which has proven to be valuable in genotype characterization as well as in population and pedigree analysis in many species. However, studies in tree crops are still meager and to date restricted to few species.

In this work we use RAPDs to distinguish 19 walnut cultivars whose pedigree is well known. RAPD profiles were scored visually as present or absent. A similarity matrix, based on the proportion of shared amplification fragments between two genotypes, was generated. A dendrogram was constructed based on the similarity data by applying unweighted pair group method with arithmetic averages (UPGMA) cluster analysis.

The results obtained produced a unique fingerprint for each of the walnut cultivars studied. UPGMA cluster analysis of the similarity matrix separated the 19 walnut cultivars in three main groups whose differences were basically determined by the original sources of the genotypes used as initial parent cultivars in the breeding program. Cultivars sharing common parents tend to group together and with at least one of the parents.

From the data obtained in this study we can conclude that RAPD technique can detect enough polymorphism to differentiate among walnut cultivars, even among genotypes closely related because of their common parentage. As a consequence, 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 different genotypes which will help in selecting the best parents to obtain new genetic combinations

Nicese, F.P., Hormaza, J.I. and Mc Granahan, G.H. (1997). CHARACTERIZATION OF WALNUT (JUGLANS REGIA L.) CULTIVARS USING RAPD. Acta Hortic. 442, 53-62
DOI: 10.17660/ActaHortic.1997.442.5

Acta Horticulturae