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Walnut (Juglans regia L.) is one of the most common nuts in the world. There are a wide walnut variety of genotypes that differ in forestry, physical and chemical properties. Most of the walnut genotypes, which are natural resources have been evaluated as promising and germplasm sources for breeding. Walnuts are high in many beneficial biochemical compounds, so they have a useful profile for many people in relation to disease risk. Therefore, the demand for production and consumption of walnut is increasing day by day. In the present study, fatty acid and tocopherol profiles of 156 F1 genotypes belonging to Chandler × Kaplan-86 walnut population and their parents were investigated. Fatty acids and tocopherol isomers (α, β, γ) were determined by GC/FID (gas chromatography/flame lonizing detector) and HPLC (high-pressure liquid chromatography) techniques, respectively. The fatty acid content of F1 walnut genotypes and their parents were found to be 0.00%-3.34% for myristic acid, 5.86%-10.05% for palmitic acid, 0.01%-4.46% for stearic acid, 0.00%-0.89% for palmitoleic acid, 10.00%-20.89% for oleic acid, 45.36%-66.20% for linoleic acid and 9.04%-20.55% for a-linolenic acid. The content of a-tocopherol, ß-tocopherol and γ-tocopherol from the walnut population were determined to be 1.61-23.65 µg/g, 1.90-12.57 µg/g, 90.22-394.96 µg/g, respectively. The Chandler × Kaplan-86 F1 hybrid walnut population showed a significant variation in terms of the fatty acids and tocopherol contents. This research contains up-to-date scientific data on very wide walnut genetic resources and composition. Our data show that 156 F1 walnut genotypes have a potential source of monounsaturated fatty acids and tocopherols and the results are very important for future breeding studies on walnut. [ABSTRACT FROM AUTHOR]

The pollen grains of 32 different walnut cultivars and types were tested in vitro to determine their viability, germination ability, and pollen production level. Viability of pollens was determined by TTC and FDA tests. The hanging drop method and agar in petri method were used for pollen germination. Pollen production of the cultigens was determined with the hemacytometric method. The rate of pollen viability of all the investigated cultigens was high (> 80%). The germination rate of the pollens ranged from 33.28% to 50.19% and the Van 4 cultivar had the highest pollen germination rate. Although similar results were obtained with the 2 germination tests, higher sucrose concentration (15%) resulted in better germination percentages. Pollen production of the walnut cultivars and types were higher than in previous reports. The range of total pollen grain production of the walnut trees was estimated to be 5-100 billion. [ABSTRACT FROM AUTHOR]

Marass 12: A Walnut Cultivar with Cluster-bearing Habit. Walnut, Juglans regia, walnut breeding, cultivars, Marasx 12, cluster bearing. [Extracted from the article]

Breeding studies in walnut (Juglans regia L.) are usually time consuming due to the long juvenile period and therefore, this study aimed to determine markers associated with time of leaf budburst and flowering-related traits by performing a genome-wide association study (GWAS). We investigated genotypic variation and its association with time of leaf budburst and flowering-related traits in 188 walnut accessions. Phenotypic data was obtained from 13 different traits during 3 consecutive years. We used DArT-seq for genotyping with a total of 33,519 (14,761 SNP and 18,758 DArT) markers for genome-wide associations to identify marker underlying these traits. Significant correlations were determined among the 13 different traits. Linkage disequilibrium decayed very quickly in walnut in comparison with other plants. Sixteen quantitative trait loci (QTL) with major effects (R2 between 0.08 and 0.23) were found to be associated with a minimum of two phenotypic traits each. Of these QTL, QTL05 had the maximum number of associated traits (seven). Our study is GWAS for time of leaf budburst and flowering-related traits in Juglans regia L. and has a strong potential to efficiently implement the identified QTL in walnut breeding programs. [ABSTRACT FROM AUTHOR]

Walnut, Juglans regia L., has been cultivated for its edible nut and timber since ancient times. It is one of the most valuable and widely cultivated horticultural commodities in the world. Simple sequence repeats (SSRs) have a wide range of applications in plants, and there is still a necessity to develop novel SSR markers for each plant species. Bacterial artificial chromosome-end sequences (BES) are good sources to generate novel SSR markers. In pursuit of this objective, a total of 558 BES-SSR primer pairs were designed for J. regia . Of them, 507 (91%) had amplifications, and 307 were polymorphic when tested in eight walnut cultivars. A total of 1097 alleles were generated from 307 polymorphic SSR loci, ranging from two to eleven, with an average of 3.6 per locus. Polymorphism information contents (PIC) varied from 0.11 to 0.88 with an average of 0.46. Di-nucleotide motifs had higher polymorphism and genetic diversity values than the other motif types. The rate of polymorphism increased with the repeat length, therefore, class I SSRs are useful source of polymorphic DNA markers in walnut. Novel SSR markers developed in this study may possess potential applications such as fingerprinting, marker-assisted breeding, germplasm characterization and genetic linkage mapping in walnut and other species of Juglans . [ABSTRACT FROM AUTHOR]

Juglans regia L. is the only commercially grown species for nut consumption within the Juglans genus. Simple sequence repeats (SSRs) are the markers of choice, especially when constructing genetic linkage maps for plants. There are only a limited number of simple sequence repeat (SSR) markers in the literature for J. regia that can be used to construct a SSR based genetic linkage map. Therefore, genomic libraries enriched with CA, GA, AAC, and AAG repeats were constructed using genomic DNA from J. regia cv. ‘Maraş-18’ to develop SSR markers for walnut. A total of 624 clones were sequenced; 516 had repeats and 94 were duplicates. Two-hundred and seventy-six primer pairs were designed, and 246 generated PCR products and 185 polymorphic loci were obtained by characterizing 15 walnut cultivars. The number of alleles ranged from two to ten among the 185 polymorphic loci with an average of 4.3. The GA-enriched library was the best among the four libraries in terms of number of alleles, polymorphism, productivity, and information content. A higher number and frequency of SSRs were obtained from the dinucleotide-enriched libraries than from the trinucleotide libraries. The SSR markers developed in this study may help genetic studies on J. regia and related species, especially when constructing and integrating maps. [ABSTRACT FROM AUTHOR]

Abstract: Turkey has a rich walnut germplasm that has arisen from populations of naturally grown seedlings over many years. Despite this enormous genetic potential, only a few studies on molecular characterization studies have been carried out so far. In this study, the genetic relationships among 59 walnut genotypes and cultivars of international and Turkish interest were analyzed by 25 RAPD primers, 25 ISSR primers, and 16 SSR primer pairs. Among the molecular assays tested, SSR provided a very high polymorphism rate of 99.1%, while ISSR and RAPD results showed similar to each other but lower polymorphism (71.1% and 69.1%, respectively). The dendrogram constructed divided the genotypes into three main groups: ‘Group A’ included mainly genotypes originating from the Kahramanmaras and Yalova provinces, while ‘Group B’ contained genotypes originating from the Kırsehir, Tokat and Corum provinces of Turkey. ‘Group C’ contained only cultivars originating from the USA and France. According to the clustering in the dendrogram genotypes grouped largely in accordance with their geographical origin, although certain exceptions were present. The pairs of ‘Akca-2’ with ‘Karabodur’ and ‘Yalova-1’ with ‘Yalova-3’ were the most closely related walnut genotypes in this study. In conclusion, our study indicated that molecular markers are useful tools for use in to determining genetic relationships among walnut genotypes. The results will provide valuable information to walnut cultivar breeding programs for use in parental selection. [Copyright &y& Elsevier]

Walnut (Juglans regia L.) is the most important species in the genus Juglans due to the high commercial value of its nuts and timber. Simple sequence repeats (SSRs) are considered as the markers of choice owing to their codominant nature. Since very few SSRs have been developed in walnut, this study aimed to develop numerous polymorphic SSRs from Class I repeats by using DNA sequences of the Chandler cultivar. In all, 800 SSRs were designed and tested in 8 Turkish, 3 French, and 5 US walnut cultivars, of which 88 (11%) did not produce bands, 161 (20.1%) were monomorphic, and 551 (68.9%) were polymorphic. In all, 2696 alleles were produced by the 551 polymorphic SSR loci in the 16 walnut cultivars, ranging from 2 to 14 alleles per locus with an average number of 4.9. Polymorphism information content ranged from 0.21 to 0.89 with an average of 0.62. Cluster analysis produced a very robust dendrogram. The walnut cultivars were separated into two main groups: all Turkish cultivars were included in one group, whereas the US and French cultivars were included in the other group. A set of 20 SSRs was selected for their high genetic diversity values to be used in further genetic studies in walnut. The novel SSR markers developed in this study could be used in future studies for constructing a genetic linkage map, analyzing population genetics, identifying parents, and conducting marker-assisted breeding, fingerprinting, and germplasm characterization in walnut. [ABSTRACT FROM AUTHOR]