Revealing genetic diversity and association mapping among Palaz hazelnut (Corylus avellana L.) clones in the East Black Sea region by morphological and ISSR/SRAP markers

This study aimed to determine the yield, nut traits, and genetic diversity of promising and phenotypically distinct Palaz hazelnut clones, as well as the markers associated with these traits. Principal component analysis (PCA) showed that the yield and nut traits could effectively explain the variability among the Palaz clones, which exhibited wide variation in terms of morphological traits. Broad-sense heritability was determined to range from 0.18 (rotten kernel) to 0.99 (trunk cross-sectional area). Key agronomic traits, including husk length (h² = 0.87), yield efficiency (h² = 0.86), nut yield per plant (h² = 0.83) and nuts per cluster (h² = 0.73), revealed strong genetic control and high selection efficiency, independent of environmental factors. Molecular characterization using ISSR and SRAP markers identified 95 loci, 89 of which were polymorphic. Principal coordinate analysis (PCoA) effectively distinguished between the clones, especifically P-3 and P-20. These clones were genetically different from the standard Palaz cultivar and the other clones. This indicates that they probably have been originated from a seedling. Of these, P3 yielded notable results in terms of yield and nut traits. It can be used to develop new cultivars in hazelnut breeding programs. In the association mapping, 67 loci were related to investigated traits. Important traits for hazelnut breeding programs were associated with pleiotropic loci [(AG)7YC-900], which could help breeders to select superior accessions regarding yield and nut traits. In conclusion, the identified loci could be useful for breeders to select individuals with the desired traits in hazelnut breeding programs. The obtained data will be a valuable resource for future breeding efforts and contribute to the conservation and sustainability of hazelnut genetic resources.