Morphological Variation, Heritability and Phenotypic Correlation of Traits Related to the Vigor in Persian Walnut (Juglans regia L.)

Considering frequent observation of low vigor (dwarf) and precocious walnut seedlings in some of Iran nurseries, and in order to understand genetic causes of this phenomenon and the effect of parental genotype on the seedling vigor and precocity, two half–sib family tests were conducted using open pollinated seeds of Persian walnut (Juglans regia L.) trees with different vigor and bearing habit. Based on the results, significant variations were found within- and between-families in terms of seedling height and diameter, number of nodes and length of internodes in both 45-day-old and one year old seedlings. Moderate to high narrow-sense heritability (0.39-0.88) was estimated for all of the traits, both by between family variance and parent-offspring regression methods. Seedling height had positive correlation with other vigor related traits indicating that measuring only seedling height is adequate to identify families that produce low vigor seedlings. In conclusion, we suggest a simultaneous recurrent selection program for both dwarfing and rooting ability (selection of dwarf/semi-dwarf as well as easy-to-root clones) to utilize their advantages in a high-density orchard system.