Relationship between Clone Age and Selection Trait Expression in Mature Walnuts

Abstract

Data on 15 traits collected from 30 walnut selections were analyzed for changes in relation to both clone and rootstock age. Data collection began at first flowering (age 3 or 4) and continued annually for up to 28 years on each clone. Significant correlations were found between seasonal timing of the expression of phenological traits and clone age. The general trend was towards earlier leafing, bloom, and time of nut maturity as the clone aged. Correlations with rootstock age were lower than with clone age for phenological traits. Shell and kernel trait expression was more highly correlated with rootstock age than clone age, suggesting that changes may be due to vigor and other effects of grafting rather than aging per se. Estimates of the age of stabilization for phenological traits ranged between 9 and 18 years from germination. It is suggested that changes in leafing, bloom, and nut maturity dates be considered prior to commercial release of walnut cultivars.

Morphological and pomological assessments of seedling-originated walnut (Juglans regia L.) trees to select the promising late-leafing genotypes

“…The date of leafing and flowering of the studied genotypes was evaluated. Since phenological traits show diversity due to differences in environmental conditions [ 23 ], the data related to these traits were adjusted based on a standard genotype. Accordingly, the earliest-leafing genotype was considered as control or reference standard and it was given the code zero and for other trees, the number of days after control or reference tree was recorded.…”

Characterisation of the agroforestry performance of 12 walnut (Juglans sp.) genotypes grown in two locations of Catalonia

“…Actualmente, en la UE sólo en Grecia existen amplias poblaciones de nogal todavía explotables, si bien por poco tiempo, ya que la superficie de nogal asilvestrado está disminuyendo muy rápidamente. Como consecuencia, la mayoría de la madera utilizada en Italia, el primer procesador mundial de nogal común, procede de Irán y Turquía y, recientemente, de algunas repúblicas centroasiáticas como el Kirguizistán (Rouskas et al, 1995;Jay-Allemand et al, 1996;Hemery, 1998;MAPA, 1999).…”