Juglans regia L. is typical of Juglandaceae in that it is monoecious, wind-pollinated, and self-compatible. Despite its self-compatibility, breeding and research programs have encountered difficulties acquiring sufficient quantities of pollen
Kourosh Vahdati, Naser Lotfi, Bahman Kholdebarin, Darab Hassani, Reza Amiri, Mohammad Reza Mozaffari, and Charles Leslie
seed or by grafting on rootstocks ( Vahdati, 2003 ). Hence, there is huge genetic diversity among rootstock traits. For example, there are many old Persian walnut ( Juglans regia L.) trees in Iran that have been planted on the banks of rivers. The long
Javiera Morales, Ximena Besoain, Italo F. Cuneo, Alejandra Larach, Laureano Alvarado, Alejandro Cáceres-Mella, and Sebastian Saa
). The high N inputs used in walnut production ( Gupta et al., 2012 ; Simorte et al., 2001 ; Weinbaum and Van Kessel, 1998) and the high susceptibility to P. cinnamomi reported in Juglans regia L. ( Guajardo et al., 2017 , 2019 ) highlight the need
Wilbur Reil, David Ramos, and Ronald Snyder
Two management systems were initiated in a 10 year old Juglans regia cv. Hartley orchard planted 8 m. × 8 m. in 1977. Annual dormant selective pruning was practiced for the next 8 years on all trees within one treatment (pruning) compared to dormant severe pruning on alternate temporary trees with no pruning on adjacent permanent trees (thinning). Temporary trees were removed in the thinning treatment in 1985.
Yield, trunk cross sectional area, pruning weight and nut quality factors were evaluated each year from the 5 replicate, completely randomized trial.
Yield and nut quality factors did not differ between the two treatments during the 15 years.
In 1990 the pruned trial was again pruned causing a 20% drop in production (p=.06). With no additional pruning yield returned to slightly above the thinned treatment in 1991.
This trial demonstrates that Hartley walnut trees (terminal bearing habit) continue to produce satisfactory crops under crowded canopy management but a tree thinning program offers other advantages which also should be considered.
Robert G. Fjellstrom, Dan E. Parfitt, and Gale H. McGranahan
RFLP markers were used to study genetic diversity among California walnut (Juglans regia L.) cultivars and germplasm collected worldwide. 16 of 21 RFLP markers were polymorphic in the 48 walnut accessions tested. Seven RFLP markers permitted unique identification of all walnut cultivars. All genotypes were heterozygous at approximately 20% of the loci for both California and worldwide germplasm. California walnut germplasm contained 65% of the worldwide allelic diversity. Cluster analysis of genetic distance between accessions and principal component analysis of allelic genotypes showed two major groups of walnut domestication. California germplasm was associated with germplasm from France, Central Europe, and Iran, and had less genotypic similarity with germplasm from Nepal, China, Korea, and Japan.
Daniel Potter, Fangyou Gao, Giovanna Aiello, Charles Leslie, and Gale McGranahan
The utility of intersimple sequence repeat (ISSR) markers for identification of English or Persian walnut (Juglans regia L.) cultivars was explored. Four cultivars were screened with 47 ISSR primers; eight of these primers, which generated reproducible and informative data, were selected for further study. Two individuals from each of 48 cultivars, including many currently important in the California walnut industry as well as accessions from Europe and Asia, were then examined with the eight ISSR primers. Polymerase chain reaction (PCR) products were separated on agarose gels and stained with ethidium bromide. Fifty-four bands were scored as present or absent in each cultivar; of these, 31 (57%) were polymorphic among the 48 cultivars. Combined data from the eight ISSR primers provided a unique fingerprint for each of the cultivars tested. Fifteen of the cultivars could be distinguished from all others with just one primer, 31 with a minimum of two primers, and two required three primers. Pairwise genetic distances between the cultivars were calculated and a dendrogram was generated using the neighbor-joining algorithm. Some of the groupings in the dendrogram corresponded to groups which, based on known pedigrees, are genealogically closely related. Others included accessions from diverse genetic and/or geographic origins. These results can be attributed to a combination of the limitations of the ISSR method for inferring genetic relationships, on the one hand, and the complex history of walnut cultivar development involving extensive exchange and breeding of germplasm from different geographic regions, on the other.
R.G. Fjellstrom, D.E. Parfitt, and G.H. McGranahan
RFLP markers were used to investigate genetic diversity among California walnut (Juglans regia) cultivars and germplasm collected worldwide. Sixteen of 21 RFLP markers were polymorphic in the 48 walnut accessions tested. RFLP markers were useful for identifying walnut cultivars. All genotypes were heterozygous at ≈20% of the loci for both California and worldwide germplasm. California walnut germplasm contained 60% of the worldwide allelic diversity. Cluster analysis of genetic distance between accessions and principal component analysis of allelic genotypes showed two major groups of walnut domestication. California germplasm was associated with germplasm from France, central Europe, and Iran and had less genotypic similarity with germplasm from Nepal, China, Korea, and Japan.
Zhan Shu, Xue Zhang, Dianqiong Yu, Sijia Xue, and Hua Wang
each tree was preserved in silica gel and taken to the laboratory for storage at −80 °C until DNA extraction and molecular marker analyses. Fig. 1. Nut morphology of Juglans cathayensis , Juglans regia , and putative hybrid. Grooves of the putative
Rohollah Karimi, Ahmad Ershadi, Kourosh Vahdati, and Keith Woeste
The family Juglandaceae consists of seven genera, comprising ≈60 monoecious tree species. The genus Juglans contains 20 species, all producing edible nuts. Among these, the English or Persian walnut ( Juglans regia ) is the most widely cultivated
Qingguo Ma, Junpei Zhang, and Dong Pei
English (or persian) walnut ( Juglans regia ) is an economically important tree species throughout temperate regions of the world as a result of its nutrient-rich nut and high-quality timber. China is considered one of the most important countries