Research Article
Fruit Characteristics of Some Turkish Walnut Genotypes and Cultivars (Juglan regia L.)
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A. Kazankaya
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A. Gun
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M.A. Askin
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H.I. Oguz
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F. Celik
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Turkey is the oldest place for settlement to many civilizations and the motherland of many fruit species because of geographic locations, diverse climatic conditions and soil types. Walnut is an important crop species among them and an ancient species originating in Turkey. Anatolia plays bridge role in extending of walnut to many Western countries[1]. Among Juglandaceae in the world, 21 species have known. The most popular walnut species spread out throughout the world that have commercial value are Juglans regia L.[1,2]. Walnuts grown in Anatolia belong to these species and produced from seedling. Because of continuous seed propagation a great number of seedling walnut trees have occurred creating valuable walnut genetic resources[1,3]. Factors used for selecting of promising genotypes vary depending on the researchers[1,3-5]. In walnut production, it is important to use standard varieties and local promising selections for commercial production. In recent years, walnut genotypes obtained from the selection propagated also by grafting. In this study, walnut genotypes and standard cultivars selected according to selection criteria grown from Denizli Province of Turkey were evaluated with regard to fruit traits.
Standard walnut trees grown naturally from seedling originated in the center of Denizli Province and subordinate villages were used. Denizli lies in west part of Turkey having 37°46N latitude and 29°04E longitude. The region was searched thoroughly during 2003 and 2004. Samples were taken from 9 expected healthy genotypes and 7 standard healthy cultivars. For measurements and evaluations, thirty samples of fruits were chosen randomly from the each tree. The evaluated fruit traits were nut weight (g), kernel weight (g), kernel yield (%)- (kernel weight/nut weight), length and width of nut (mm), cheek, color of shell and kernel, shell thickness (mm), roughness of shell, kernel fullness, kernel defect, shell breakage, shell streak, shriveled kernel (%)[1,4,6]. The average values for each trait were reported.
Good kernel quality is desirable and important properties for walnut cultivar improvement. Walnut fruit traits varied in nut size and kernel yields depending on genotypes and cultivars (Table 1 and 2).
Table 1: | Nut traits of studied walnut varieties in Denizli Province |
Table 2: | Nut traits of studied walnut varieties in Denizli Province |
Nut traits of the genotypes ranged from 8.62 (DE 83) to 15.70 g (DE 64) for nut weights; from 3.84 (DE 03) to 8.36 g (DE 80) for kernel weights; from 34.07 (DE 03) to 61.83% (DE 80) for kernel yield. The genotypes had a range of 35.36 (DE 83) to 43.19 mm (DE 101) for nut lengths, 29.82 (DE 01)-35.78 mm (DE 44) for nut width, 30.40 (DE 01)-38.16 mm (DE 64) for check and 1.12 (DE 83)-2.02 mm (DE 03) for nut shells(Table 1 and 2).
In standard cultivars, nut weights varied from 7.82 (Altınova) to 24.34 g (Kaplan 86), kernel weights from 4.10(Altınova) to 10.30 g (Kaplan 86), kernel yield from 39.44 (Yalova 2) to 61.55% (Şebin), fruit lengths from 31.43 (Altınova) to 54.40 mm (Kaplan 86), fruit width from 27.00 (Altınova) to 45.48 mm (Kaplan 86), cheeks from 28.91(Altınova) to 45.50 mm (Kaplan 86), shell thicknesses from 1.34 (Yalova 4) to 2.04 mm (Yalova 2)(Table 1).
Harvest period of genotypes and standard cultivars extended from early September to mid-October as (Table 2). Most genotypes had fruit ripening period from mid-September to late-September. Ripening period of native standard cultivars was mostly late-September. In general, genotypes and standard cultivars had no shriveled and bruised kernel. The kernels were removed as whole and the shell colors were moderate. Shell breakage was mostly easy. The selections had also no shriveled and bruised kernels.
Differences were found in fruit and kernel weight and kernel yield among the standard cultivars in the earlier study[3]. Fruit weights of Yalova 1, Yalova 2, Yalova 3, Yalova 4 and Şebin as standard cultivars were 15.5, 16.5, 12.1, 12.9 and 9.4, respectively. Kernel weights were 7.5, 7.6, 6.4, 6.8 and 6.6, respectively. The highest ratio obtained in Şebin with 63%, Yalova 3 and Yalova 4 followed that with 53%. Yalova 2 and Yalova 1 had the ratio of 46 to 48%, respectively. In this study, Şebin also had the highest kernel yield with 61.55%, Yalova 3 and Yalova 4 followed that with 59.56 and 54.43%. In another study accomplished in the Malatya with the same standard cultivars, from the high to low kernel ratios were belong to Şebin, Yalova 1, Yalova 3 and Yalova 2 with the value of 58.7, 49.6, 47.1, 39.7%. Şebin had the lowest nut weight (8.2 g), but the highest kernel yield[7]. The performance of Yalova 1, 2 and 3 cultivars in Denizli was better than that grown in the other locations. Yalova 4 and Şebin had the similar fruit traits as performed in the other location. In the study carried out in Çameli and Bozkurt districts of Denizli Province nut weights were found between 12.56 and 18.40 g, kernel weights between 7.61 and 9.92 g, kernel yield between 53.49 and 64.27%, shell thickness between 0.83 and 1.36 mm[8]. In terms of kernel attributes, kernel weight over 7 to 8 g, kernel yields over 50% and light colored kernels are desirable in the selection of walnut varieties. Selection for high nut quality should include increased kernel weight and increased kernel yield and low shell weight.
Several studies on walnut genotypes in Turkey yielded various findings. The most important consideration from these studies is that Turkey has rich population in terms of walnut genotypes. In one study accomplished in Bahçesaray of Van Province in Turkey, nut weight varied from 9.7 to 17.6 g, kernel weight from 5.35 to 8.09 g, kernel ratio from 47 to 66%, shell thickness from 1.00 to 1.90[9]. In another study carried out in Çatak of Van for determination of walnut fruit traits, nut weights changed from 4.21 to 11.31 g, kernel weight from 1.47 to 5.23 g, kernel ratio from 24 to 57%, shell thickness from 0.76 to 2.06 mm; nut weight at the second year from 6.54 to 13.45 g, kernel weight from 2.13 to 5.80 g, kernel yield from 27 to 57%, shell thickness from 0.98 to 2.20 mm[10]. Similar results from native selection studies were obtained by some other researchers[1,11-14].
In one another study carried out in the east black sea region of Turkey, 15 native genotypes were found as promising. The genotypes had a range of 11.8 to 18.7 g for nut weight, 6.25 to 9.23 g for kernel weight, 48 to 60% for kernel yield[15]. In another selection study performed in the district of Gevaş located in the Lake Van Region of Eastern Anatolia, selections had nut weight between 10.38 to 17.04 g, kernel weight between 5.85 to 7.88 g, kernel ratio 45.09 to 59.27%, shell thickness between 0.86 to 1.75 mm and light colored[16].
The study revealed that native walnut genotypes from this location were found as promising in terms of fruit traits. Nut traits of genotypes and cultivars selected for the study found similar to that of walnuts grown in the other regions of Turkey or even better. Among the samples, kernel yields over 55% indicate the superiority of 6 genotypes used in the study. Because walnut production is under relatively high genetic control further information on the nature and degree of genetic diversity present in walnuts in the area would help to identify the valuable trees to produce uniform nuts and kernels of desirable quality.