Genetic evaluation of Paradox (a valuable walnut hybrid) resources in Iran based on leaf morphological traits

Walnut (Juglans L.) is one of the most important plant resources for the edible nuts and high-quality wood production. Paradox is a famous rootstock in the walnut industry for fast growth and resistance to some diseases that raised and described by Luther (۱۸۹۳,۱۸۹۸) in California. The samples of this hybrid collected from California and planted in Kamalshahr research station of the Horticultural Research Department. The genetic background of Paradox that commonly refers to black walnut-Persian walnut hybrid is not generally known. The results of Sue et al (۲۰۱۲) study based on nuclear sequences (IGS۸-ETS۱) indicated that Persian walnut(Juglans regia) and six black walnut species, Juglans hindsii, Juglans californica, Juglans major, Juglans nigra, Juglans microcarpa, Juglans hirsuta, are involved in the genetic formation of Paradox hybrids. Leaf morphological traits have a special place in the classification of plants. Based on McGranahan et al (۱۹۸۷) study, Paradox hybrids are readily distinguished from their black walnut parents by their leaf morphology, which is intermediate between balck and Persian walnuts. Morphological study and genetic evaluation of valuable sources of paradox seems necessary. In this study, with the aim of genetic evaluation of Paradox resources in Iran, eight leaf morphological features of these specimens including total leaf length, leaflet length, leaflet width, leaflet number, leaflet hairs, leaflet margins, leaflet shape, leaflet bases, in comparsion to Persian walnut (J. regia) and black walnut species (section Rhysocaryon) have been examined. Based on PCA and PCoA analysis, the Paradox samples are placed in an intermediate position between Persian walnut (J. regia) and California black walnut (J. californica). Therefore, J. californica is the most likely species of black walnuts that is involved in the genetic formation of these specimens. The use of molecular markers can be effective in defining and confirming the genetic background of paradox sources in Iran.

کلیدواژه ها:

Morphological features ، Genetic background ، Paradox hybrid ، Walnut