Similarities of leafing and leaf fall date of 'Pedro' walnut variety with its progenies in breeding programs

In this research, 'Pedro' walnut variety (maternal parent) was open pollinated. Offspring genotypes were compared with their maternal parent in terms of morphological and molecular features. Leafing and leaf fall dates were measured as two phenological traits. Genetic differences were identified by molecular fingerprinting using twelve Inter Simple Repetitive Sequence Polymorphism (ISSR) primers. In some progenies, leafing and leaf fall occurred later than the maternal parent ('Pedro'). Progenies were grouped according to their similarities with the maternal parent regarding leafing date. Specifically, 14.44% of the progenies were 'Very close' to the parent, 16.66% were 'Close', 30.00% 'Far' and 38.89% 'Very far'. Regarding the leaf fall date, 7.78% of the progenies were 'Very close' to the parent, 28.88% were 'Close', 36.66% 'Far' and 26.67% 'Very far'. A total of 43 bands were obtained in molecular analyses. These bands were largely polymorphic (95.34%). The average number of the alleles was 3.90, while the polymorphism information content varied between 0.14 and 0.91 among the genotypes. Genetic distances were tested according to the UPGMA (Unweighted Pair Group Method with Arithmetic Average) and by The Structure Analysis. The UPGMA dendrogram divided the genotypes into two main clusters and the similarity coefficient of the genotypes varied between 0.61 and 0.99. This study revealed that 'Pedro' can be used as an excellent parental variety in hybridization programs which prioritize late-leafing in walnut breeding. Furthermore, ISSR primers can be safely used for fingerprinting walnuts in general.