ABSTRACT
This study was conducted on Siirt Pistachio variety (Pistacia vera L.) grown in five different locations (Kahramanmaraş, Pazarcık, Gaziantep, Ceylanpınar and Siirt) for two years (2017 and 2018). Phenological (bud burst, beginning of flowering, full-bloom, and beginning of leafing end of flowering), pomological (fruit size, fruit weight, and color parameters), physical (split, unsplit fruit ratios, empty and full fruit ratio) and biochemical (total phenolics, flavonoids, antioxidant activity, and fatty acids) analyses were conducted. Total protein contents varied between 18.55% (Ceylanpınar) and 19.45% (Gaziantep); fatty acid contents between 52.80% (Siirt) and 54.25% (Gaziantep); saturated fatty acid ratios between 10.44% (Gaziantep) and 11.58% (Pazarcık); unsaturated fatty acid ratios between 88.42% (Pazarcık) and 89.56% (Gaziantep); saturated fatty acid/unsaturated fatty acid ratios between 7.64% (Pazarcık) and 8.58% (Gaziantep); total phenolics between 18.91 (Ceylanpınar) and 23.04 mg GAE/g; total flavonoids between 7.34 (Ceylanpınar) and 10.23 mg QE/g; antioxidant activity values between between 1.65 (Siirt) and 3.25 IC50 µg/ml (Kahramanmaraş). Principal component analysis revealed that four components had eigenvalues greater than 1. The first two components explained 64.6% of total variation. Oleic (−0.98) and linoleic (0.91) acids were the most effective parameters on the first component and kernel weight, a*, protein, arachidic, gonolic acids, Mg, P and Zn were the most effective parameters on the second component. Present findings can guide new studies to be done with this species.
Introduction
Pistachio (Pistachio vera L.) belongs to Anacardiaceae family and is a dioecious, deciduous and wind-pollinated species. This family includes cashew (Anacardium occidentale L.), ambarella (Spondias dulcis Forst.), mango (Mangifera indica L.), purple mumbin (Spondias purpurea L.), pepper tree (Schinus spp.), poison ivy and poison oak (Toxicodendron spp.) and sumac (Rhus coriaria L.) species (Hormaza and Wünsch, Citation2007). Pistacia species can be cultivated economically in places between 30 and 45 latitudes of the northern and southern hemispheres and in microclimates at these latitudes (Bilgen, Citation1973). Near East (high altitudes of Asia Minor, Iran and Turkmenistan) is the homeland and important gene sources of pistachio. Pistachio species are quite rich in nutrients and can be grown in dry, stony and poor soils. Therefore, they are also so called as “Golden Tree,” “Green Gold,” “King of Fruits” and “Fruit of Kings” (Ayfer, Citation1959). Culture of pistachio species dates back to ancient times. It is known that pistachios were first cultivated by Hittites who settled in the Southeastern Region of Anatolia and were consumed at the king’s tables at that time (Lemaister, Citation1959). Pistachios were first brought to European continent by Vitellius, the Governor of Syria in the 1st century (Idem, Citation1994). While pistachio spread to Spain, Italy, Sicily, France and North Africa, it was also known in countries such as Iran, Afghanistan and India where wild trees were abundant. Pistachio was introduced to the USA in the second half of the 20th century (Hormaza and Wünsch, Citation2007).
Southeastern Anatolia region of Türkiye is an important gene center of pistachio. It is where pistachio was first cultivated and its unique ecology has enabled the successful cultivation and spread of this fruit (Ayfer, Citation1959). Pistachio is a thrifty plant in all respects and is resistant to poor conditions and drought (Spiegel-Roy et al., Citation1977). These characteristics have made it possible to grow pistachios economically in rocky, stony, poor and calcareous soils of the Southeastern Anatolia Region (Ayfer et al., Citation1986). Commercial pistachio varieties are pomologically divided into two groups as Long (Long, Red, Halebi) and Round (Siirt, Ohadi). In Türkiye, mostly long pistachio varieties have been cultivated for a long time. Long pistachios are more flavorful than round pistachios, but show more alternate bearing (periodicity) (Tekin, Citation1990).
In this study, phenological (bud burst, beginning of flowering, full-bloom, beginning of leafing, end of flowering), pomological (fruit size, fruit weight, color analyses) and physical (yield, percentage of cracking) analyses were carried out on Siirt pistachio variety grown in five different locations (Kahramanmaraş, Pazarcık, Gaziantep, Ceylanpınar and Siirt) in Southeast Türkiye for 2 years (2017–2018). Fruit development was monitored in four different pre-harvest periods (between 29 May and 19 July) in 2018, and location-based course of fruit development was also followed.
Materials and Methods
Materials
Siirt pistachio variety, which has an important place in pistachio production and trade of Türkiye, was used as the material of this study. Siirt pistachio variety is mostly grown in Siirt and Şanlıurfa provinces. The tree has a semi-erect appearance and strong growth. Young shoots are light brown in color. Fruit buds are oval and light brown. Flowers are cream colored. It is a medium-late variety with a chilling requirement of 700 h and a total temperature requirement of 4106 days-degree. Leaves are large, thick and light green in color and defoliation is late. Clusters are sparse and fruits are easily removed from the cluster. Fruits are large and oval, with pinkish cream outer color and bone-colored hard skin. Ripening time is middle-late period and seed color is yellow. Alternate bearing tendency (periodicity) is low (Ak, Citation1992).
Methods
Phenological and Pomological Analyses
Phenological, fruit development (2018 only), pomological and physical characteristics of Siirt variety grown in Kahramanmaraş (altitude 930 m), Pazarcık (720 m), Gaziantep (860 m), Ceylanpınar (400 m) and Siirt (1000 m) locations in southeast of Türkiye () were determined. Soil analysis results for the locations are presented in . The dates of bud burst, beginning of flowering, full-bloom, beginning of leafing and end of flowering were recorded as phenological observations. In 2018, nut and kernel growth were measured 4 times at approximately 15-day intervals throughout the season to monitor fruit growth. In this sense, depending on location, measurements were made between 29 May and 19 July. Fruit and kernel growth [fruit weight (g), fruit size (mm) and % yield] of 20 fruits were recorded. In terms of physical characteristics of the variety, percentages of split and unsplit nuts, empty and full nuts were determined with the use of 100 fruits for two years. For pomological analyses, 100 fruits were taken from 5 randomly selected trees in each replicate at each location; fruit weights (g), fruit size (mm), % yield [(kernel weight/shelled fruit weight) × 100], kernel color (L*, a*, b*) values were determined.
Figure 1. The research site (Southeast Anatolia – Türkiye).
Table 1. Soil analysis results for different locations (year 2017).
Protein Analysis
Kjeldahl method was used to determine sample nitrogen (N) contents. Resultant % nitrogen content was multiplied by a factor of 6.38 to get % protein content.
Fatty Acids Analysis
Methylation of fatty acids: About 0.1 g of oil was taken and placed into a 15 ml capped tube, then supplemented with 1 ml 2N methanolic KOH solution and vortexed for 2 min. Following 15 min waiting period, fatty acids were converted into methyl esters at this stage (if ethanol was used, it becomes ethyl ester). Resultant mixture was supplemented with 10 ml hexane and mixed thoroughly. After that, 1 µl of the supernatant was injected into a GC device. After fatty acids were methylated, they were analyzed in flame ionising detector (FID) and Shimadzu Gas Chromatography (Model 2025). Supelco 37 Component Mix certified STD obtained from Supelco was used in the analyses.
Total Phenolics
Folin-Ciocelteu Recactive (FCR) method was used to determine total phenolics of the extracts in accordance with the procedures specified in Blainski et al. (Citation2013). Gallic acid (Sigma) was used as the standard. The prepared solutions were read in a spectrophotometer at a wavelength of 750 nm. Results were expressed in mg gallic acid equivalent/g dry weight.
Total Flavonoids
Total flavonoids of the extracts were determined spectrophotometrically in accordance with Tunç et al. (Citation2024a, Citation2024b). Absorbance readings were performed in a spectrophotometer at 415 nm wavelength. Results were expressed in μg quercetin equivalent/g dry weight.
Antioxidant Capacity (DPPH Method)
DPPH method was used as described by Brand-Williams et al. (Citation1995) to determine antioxidant capacity of the extracts. Solution series were diluted to get five different concentrations. Results were presented as IC50 value, which is the concentration value required to reduce half of the DPPH free radicals. All experiments were performed in three replicates, and ascorbic acid was used as the positive control.
Elemental Analysis
Some of the plant samples were taken into a separate tube. About 1 g of the sample portions were taken and acid-digested (HNO3/HCl) in a microwave. Element concentrations (Ca, Mg, P, K, Fe, Zn, Cu, Mn and Na) were determined with the use of an ICP-OES (Optima 2100 DV: PerkinElmer Inc.) device.
Statistical Analysis
SPSS analysis software was used for statistical analysis. Experiments were conducted in completely randomized blocks design with three replications. Experimental findings were subjected to analysis of variance, and significant means were compared with the use of Duncan’s multiple range test.
Results and Discussion
Phenological Observations
Findings on phenological observations of Siirt pistachio cultivar grown under different ecological conditions in 2017 and 2018 are given in . There were differences between locations at all phenological dates. In 2017, the earliest bud burst was observed on 28 Apr. at Gaziantep and Ceylanpınar locations and the latest bud burst was observed on 6 Apr. at Pazarcık location. In 2018, the earliest bud burst was observed on 21 Mar. in Gaziantep and the latest on 27 Mar. at Kahramanmaraş and Siirt locations. In terms of flowering onset, the earliest flowering was observed on 5 Apr. in Gaziantep and the latest flowering was observed on 13 Apr. in Kahramanmaraş in 2017. In 2018, the earliest flowering was observed on 28 Mar. at Gaziantep and Ceylanpınar locations and the latest flowering was observed on 5 Apr. in Kahramanmaraş. In terms of full-bloom dates, the earliest full-bloom was observed in Gaziantep and Ceylanpınar in 2017 (11 Apr.) and in Gaziantep (2 Apr.) in 2018. Kahramanmaraş was the latest in full-bloom in both years. While similar dates were observed for the beginning of leafing in 2017, Gaziantep was the earliest location with 3 Apr. and Kahramanmaraş was the latest location with 10 Apr. in 2018. In terms of the end of flowering, 15 Apr. (Gaziantep and Ceylanpınar) was the earliest and 21 Apr. (Kahramanmaraş) was the latest in 2017. In 2018, 7 Apr. (Gaziantep and Ceylanpınar) was the earliest and 12 Apr. (Kahramanmaraş location) was the latest. Parallel to climate data, phenological observation dates were later in 2017, while all phenological stages were completed earlier in 2018 with higher temperatures compared to the previous year.
Table 2. Phenological observation dates of Siirt pistachio variety in different locations.
Physical Parameters of Ripened Fruits
The physical parameters of ripe fruits of Siirt pistachio variety at five different locations (split fruit ratio, unsplit fruit ratio, empty fruit ratio, full fruit ratio and filling ratio) are given in . In 2017, the highest split fruit ratio (87.26%) was observed at Siirt location and the lowest value (65.55%) was observed at Kahramanmaraş location. In 2018, the highest value (84.24%) was observed at Siirt location and the lowest value (62.27%) was observed at Kahramanmaraş location. Various studies have been carried out on Siirt pistachio variety in Turkey. Atlı et al. () reported the split fruit rate as 98%. In another study on Siirt variety grown under rain-fed conditions in Ceylanpınar, the split fruit rate was reported as 63.31% (Ak, Citation1997). Eryılmaz (Citation1993) reported the average split fruit rate of Siirt variety as 92%. In a study conducted in Gaziantep province between the years 1984 and 1987, the average split fruit rate of Siirt variety was reported as 86% (Karaca and Nizamoğlu, Citation1994). In a study conducted in Aydın province, fruit splitting rates were reported as between 77.33% and 85.33% (Seferoğlu et al.,). In another study conducted in Gaziantep, Şanlıurfa, Kahramanmaraş and Adıyaman provinces between the years 1985 and 1992, the split fruit rate of Siirt variety was reported as 94% (Tekin and Akkök,). Özdemir (Citation2013) reported the split fruit rate of Siirt variety as 85.59%. The present findings regarding the split fruit rates of different locations are compatible with the previous findings. It can be said that location, climate and growing conditions were highly effective in split fruit formation.
Table 3. Physical parameters of ripened fruits of Siirt pistachio variety (mean of the years 2017–2018).
Full fruit ratios of Siirt pistachio variety grown in different locations varied between 96.58% (Ceylanpınar) and 88.07% (Kahramanmaraş) in 2017 and between 94.41% (Ceylanpınar) and 87.14% (Kahramanmaraş) in 2018. Özdemir (Citation2013) conducted a study in Ceylanpınar and reported the total full fruit rate of Siirt variety grafted on Pistacia vera L. rootstock as 87.89%. In another study, Başarıcı (Citation2017) reported the full fruit rate as 93.33%.
Empty fruit rates of Siirt pistachio variety varied between 11.93% (Kahramanmaraş) and 3.42% (Ceylanpınar) in 2017 and between 12.86% (Kahramanmaraş) and 5.59% (Ceylanpınar) in 2018 (). It was reported that empty fruit rates decreased and split and full fruit rates increased in pistachios grown under rain-fed conditions (Hormaza and Wünsch, Citation2007:22). Ak (Citation1997) conducted a study under rain-fed conditions of Ceylanpınar and reported the average empty fruit rate of Siirt pistachio variety as 13.05%. Özdemir (Citation2013) reported the empty fruit rate of Siirt variety grafted on Pistacia vera L. rootstock as 12.1%. Başarıcı (Citation2017) reported the empty fruit rate of Siirt variety as 6.67%.
In 2017, the highest unsplit fruit ratio (34.45%) was observed in Kahramanmaraş location and the lowest value (12.74%) was observed in Siirt location. In 2018, the highest value (37.73%) was observed in Kahramanmaraş location and the lowest value (15.76%) was observed in Siirt location. In 2017, the highest unsplit full fruit ratio (22.06%) was observed in Kahramanmaraş location, and the lowest value (8.33%) was observed in Siirt location. In 2018, the highest value (24.87%) was observed in Kahramanmaraş location and the lowest value (9.51%) was observed in Siirt location. In 2017, the highest kernel ratio (51.95%) was observed in Ceylanpınar location and the lowest value (49.57%) was observed in Gaziantep location. In 2018, kernel ratios varied between 60.00% (Pazarcık location) and 56.34% (Siirt location). In previous studies on Siirt pistachio variety, kernel ratios were reported as between 46.07% and 60.47% (Seferoğlu et al.,), as 49.9% (Özdemir, Citation2013), as 45% (Atlı et al.,), as 44% (Karaca and Nizamoğlu, Citation1994), as 43.9% (Tekin and Akkök,) and as 42% (Eryılmaz, Citation1993). The present findings regarding the kernel ratios of Siirt variety are compatible with the previous findings.
In 2017, the highest kernel weight (0.83 g) was observed at Ceylanpınar location and the lowest value (0.76 g) was observed at Gaziantep location (). In 2018, the highest value (0.83 g) was observed at Ceylanpınar and Gaziantep locations and the lowest value (0.72 g) was observed at Kahramanmaraş location. Eryılmaz (Citation1993) reported the average kernel weight of Siirt variety as 0.57 g. The present kernel weights were higher than the values of Eryılmaz (Citation1993).
Table 4. Pomological parameters of ripened fruits of Siirt pistachio (mean of the years 2017–2018).
The 100-kernel weights of Siirt variety varied between 82.29 g (Ceylanpınar) and 69.98 g (Kahramanmaraş) in 2017 and between 82.54 g (Gaziantep) and 65.98 g (Kahramanmaraş) in 2018 (). In a study conducted on Siirt variety in Aydın province of Türkiye, 100-kernel weights were reported as between 52 and 70 g (Seferoğlu et al.,).
In terms of internal brightness (L*) values of Siirt pistachio variety, the highest values were obtained from Siirt location (66.35 and 61.10) and the lowest values were obtained from Gaziantep location (62.95 and 53.33) in both years (). Söğüt (Citation2016) conducted a study in Nizip district of Gaziantep province and reported the L* value of Kırmızı variety as 53.99. Şahin (Citation2017) conducted a study in Suruç district of Şanlıurfa province and reported the L* value of the same variety as 62.27.
The a* values of Siirt variety grown in different ecologies varied between 0.98 (Kahramanmaraş) and 2.79 (Pazarcık) in 2017 and between 1.11 (Kahramanmaraş) and 5.02 (Pazarcık) in 2018. Söğüt (Citation2016) reported a* value of Kırmızı variety as 2.53 and Şahin (Citation2017) reported a* value of the same variety as 1.44.
In terms of yellowness (b*) values of Siirt variety, the highest value (37.67) was observed at Siirt location and the lowest value (30.61) was observed at Ceylanpınar location in 2017. In 2018, the highest value (38.12) was observed at Kahramanmaraş location and the lowest value (29.28) was observed at Gaziantep location (). Söğüt (Citation2016) reported the b* value of Kırmızı variety as 30.72 and Şahin (Citation2017) reported the b* value of the same variety as 36.28.
Pomological Parameters of Ripened Fruits
Fruit weight (g), 100-fruit weight (g), fruit length (mm), fruit width (mm) and fruit thickness (mm) values of Siirt variety grown in five different locations are provided in . In 2017, the highest fruit weight (1.44 g) was observed at Siirt location and the lowest value (1.32 g) was observed at Kahramanmaraş and Gaziantep locations. In 2018, the highest value (1.43 g) was observed at Gaziantep location and the lowest value (1.25 g) was observed at Kahramanmaraş location. Eryılmaz (Citation1993) reported the average fruit weight of Siirt variety as 1.3 g. The 100-fruit weights varied between 139.94 g (Ceylanpınar) and 123.23 g (Kahramanmaraş) in 2017 and between 141.69 g (Siirt location) and 112.88 g (Pazarcık) in 2018. In previous studies, 100-fruit weight of Siirt variety was reported as 135.10 g (Atlı et al.,), as 132.49 g (Ak, Citation1997), as between 112.00 and 112.60 g (Seferoğlu et al.,) and as 118.20 g (Başarıcı, Citation2017). Present findings on 100-fruit weights are similar to the findings of previous researchers.
Biochemical Analysis of Ripened Kernels
Total fatty acid content and fatty acid composition of Siirt pistachio variety are given in . Average fatty acid content was 53.66 ± 0.58. For fatty acid composition, myristic (0.0810–0.1080), palmitic (10.2275–11.10750), stearic (1.11010–11.2700), arachidic (0.3855–0.6300), palmitoleic (0.8175–1.0180), oleic (48.9615–55.2435), linoleic (30.4820–36.8840), linolenic (0.3590–0.8405) acids were the major components. Oleic acid was the most common monounsaturated fatty acid (). Linoleic acid has the highest percentage among polyunsaturated fatty acids (Abdoshahi et al., Citation2011). Similar results were also reported by the previous researchers (Abdoshahi et al., Citation2011; Esteki et al., Citation2018; Mahmoodabadi et al., Citation2012; Okay, Citation2002; Özrenk et al., Citation2012; Polari et al., Citation2019).
Figure 2. Fatty acid composition of Siirt variety at GC.
Table 5. Fatty acid composition of the Siirt pistachio variety in different locations.
Total protein and saturated/unsaturated fatty acid ratios of Siirt pistachio variety are given in . As can be seen in this table, the highest protein ratio was found in Kahramanmaraş (19.25%) and Gaziantep (19.45%). Although the total fatty acid data were close to each other, the highest ratio was observed in Gaziantep (54.25%) and Pazarcık (54.10%). The highest saturated fatty acid ratios were observed in Kahramanmaraş and Pazarcık locations (11.19% and 11.58%). Also, unsaturated fatty acid ratios were almost equal in all locations. The highest unsaturated/saturated (%) fatty acid ratios were observed at Gaziantep and Ceylanpınar locations (8.58 and 8.55%). Present findings are quite compatible with the findings of Okay (Citation2002), Abdoshahi et al. (Citation2011), Mahmoodabadi et al. (Citation2012), Özrenk et al. (Citation2012), Esteki et al. (Citation2018), Polari et al. (Citation2019).
Table 6. Total protein, saturated and unsaturated fatty acid ratios of Siirt pistachio variety in different locations.
Total phenolics, flavonoids and antioxidant activity of Siirt pistachio variety grown in different locations are presented in . Total phenolics varied between 18.91 (Ceylanpınar) and 23.04 mg GAE/g (Kahramanmaraş); total flavanoids varied between 7.34 (Ceylanpınar) and 10.23 mg QE/g (Kahramanmaraş); antioxidant activity values varied between 1.65 (Siirt) and 3.25 IC50 µg/ml (Kahramanmaraş). Present total phenolics and antioxidant activity values are different from those of Gündeşli (Citation2020), Sharifkhah et al. (Citation2020), Tsantili et al. (Citation2011). Such differences were attributed to alternate bearing and different climate, location, diversity, soil structure and cultural processes (Tomás‐Barberán and Espín, Citation2001). Present total flavonoids were similar to the findings of Tsantili et al. (Citation2011).
Table 7. Total phenolics, flavonoids and DPPH antioxidant activity of Siirt pistachio variety in different locations.
Macro and micro element contents of Siirt pistachio variety at five different locations (Kahramanmaraş, Pazarcık, Gaziantep, Ceylanpınar and Siirt) are provided in . Ca contents varied between 163.2 ppm (Gaziantep) and 183.6 ppm (Siirt), Mg contents between 25 ppm (Kahramanmaraş) and 29. 78 ppm (Siirt), P contents between 470 ppm (Kahramanmaraş) and 495 ppm (Pazarcık), K contents between 514 ppm (Gaziantep) and 546 ppm (Siirt), Fe contents between 2.64 ppm (Ceylanpınar) and 3.26 ppm (Gaziantep), Zn contents between 2.1 ppm (Pazarcık) and 2.77 ppm (Siirt), Cu contents between 7. 26 ppm (Gaziantep) and 7.73 ppm (Kahramanmaraş), Mn contents between 28.19 ppm (Pazarcık) and 29.76 ppm (Kahramanmaraş) and Na contents between 8.32 ppm (Pazarcık) and 11 ppm (Ceylanpınar). Pazarcık location was characterized by Ca (183 ppm), Mg (31 ppm) and P (495 ppm), Siirt location by Ca (183.6 ppm), K (546 ppm) and Zn (2.77 ppm) and Gaziantep location by Fe (3.26 ppm). Macro- and micro-element contents of pistachios are influenced by different factors such as genetic structure of the variety, climate and environmental conditions (Tomás‐Barberán and Espín, Citation2001).
Table 8. Macro and micronutrient content of Siirt pistachio variety in different locations.
Principle Component Analysis
Principal component analysis revealed that four components had eigenvalues of above 1. The first two components explained 64.6% of the total variation. The 1st component included L*, b*, oil, palmitoleic, linoleic, oleic, stearic acids, total phenolics, Ca, K, Fe, Cu, Mn and explained 38.6% of the total variation. Oleic acid (−0.98) and linoleic acid (0.91) were the most effective parameters on the 1st component. The second component explained 26.0% of the total variation and included kernel weight, a*, protein, arachidic, gonolic, Mg, P and Zn. P (0.98) and Mg (0.88) were determined as the most effective parameters on the 2nd component. Region-based assessments revealed that Kahramanmaraş was prominent for arachidic acid, Zn, Mn, Cu and Na; Gaziantep for protein, oil, oleic, myristic, gonolic acids, total phenolics, total flavonoids, DPPH and Fe; Siirt for b*, L*, linolenic, linoleic, palmitoleic acids, Ca and K; Pazarcık and Ceylanpınar for fruit weight, kernel weight, kernel ratio, a*, stearic, palmitic acids, P and Mg ().
Figure 3. Biplot graph based on nut and biochemical properties of Siirt pistachio cultivar grown in different region.
Conclusion
Pistachio cultivation is an important source of income in Türkiye and Siirt variety has a great commercial importance in pistachio cultivation. Therefore, several studies have been regularly carried out on this variety at different times and places. The data obtained from these studies provide important guidance to breeders in establishing modern orchards with adequate pollinator male trees, selection of important and hardy rootstocks such as P. khinjuk, P. atlantica and UCB-I and P. integerrima. The data can also be useful in determining appropriate planting spacing, increasing yield and quality through proper and timely cultural practices such as irrigation, fertilization, pruning and spraying. Especially irrigations in June and July, when fruit growth takes place, reduces the rate of empty fruit and facilitates shoots of the subsequent years. Pomological and physical analyses may vary from region to region. Present findings provided important information on what to pay attention in each period of Siirt pistachio variety. Further research is recommended on the other commercial varieties for high yield and quality in pistachio cultivation.
Disclosure statement
No potential conflict of interest was reported by the author(s).
References
- Abdoshahi, A., S.A. Mortazavi, A.A. Shabani, A.H. Elhamirad, and M. Taheri. 2011. Evaluation of protein, fat and fatty acids content of the pistachio (pistacia vera L.) cultivars of Damghan, Iran. International Journal of Nuts and Related Sciences 2(4):15–24.
- Ak, B.E. 1992. Effects of pollens of different pistachio species on fruit set and quality of pistachios, Cukurova University, Institute of Science, Adana, 211s, PhD Thesis.
- Ak, B.E. 1997, August. The yield and fruit quality of Pistacia vera L. Siirt grown at Ceylanpınar state farm. Davis, California, USA: The Second International Symposium on Pistachios and Almonds, pp. 24–29.
- Ayfer, M. 1959. Studies on fertilization biology of pistachio. Ankara Univ. Fac. Agric. Publications 148, Studies. 93:104.
- Ayfer, M., U. Aysel, and F. Baş. 1986. Turkish Hazelnut Varieties. Black Sea Region Hazelnut Exporters Association, Giresun, Türkiye.
- Başarıcı, M.F. 2017. Determination of phenological and pomological properties of domestic and foreign pistachio varieties in Akçakale conditions. Kahramanmaraş Sütçü İmam University, Institute of Science and Technology, Kahramanmaraş, Türkiye, Master’s Thesis.
- Bilgen, A.M. 1973. Pistachio, Ministry of agriculture and livestock publications. 123
- Blainski, A., G.C. Lopes, and J.C.P. De Mello. 2013. Application and analysis of the folin ciocalteu method for the determination of the total phenolic content from limonium brasiliense L. Molecules 18(6):6852–6865. doi: 10.3390/molecules18066852.
- Brand-Williams, W., M.E. Cuvelier, and C.L.W.T. Berset. 1995. Use of a free radical method to evaluate antioxidant activity. LWT-Food Sci. Tech. 28(1):25–30. doi: 10.1016/S0023-6438(95)80008-5.
- Eryılmaz, A. 1993. Pistachio variety catalogue. TOKB. Publication No: 361, Ankara, Türkiye.
- Esteki, M., P. Ahmadi, Y. Vander Heyden, and J. Simal-Gandara. 2018. Fatty acids-based quality index to differentiate worldwide commercial pistachio cultivars. Molecules. 24(1):58. doi: 10.3390/molecules24010058.
- Gündeşli, M.A. 2020. Determination of sugar, total phenol contents-and antioxidant activity of various parts ‘Uzun’pistachio cultivar (pistacia vera L.). Int. J. Agric. Environ. Food Sci. 4(1):62–69. doi: 10.31015/jaefs.2020.1.8.
- Hormaza, J.I., and A. Wünsch. 2007. Pistachio. Fruits and Nuts. 113(1):243–251.
- Idem, G. 1994. Seasonal changes in mineral matter and carbohydrates in pistachio (P. vera L.) and buttum (P. khinjuk L.) seedling rootstocks and grafted pistachio trees in Şanlıurfa conditions. Çukurova University Institute of Science and Technology, Adana, PhD Thesis.
- Karaca, R., and A. Nizamoğlu. 1994, September. Quality characteristics of Turkish and Iranian pistachio cultivars grown in Gaziantep. In I International Symposium on Pistachio, Adana, Türkiye, 419, 307–312.
- Lemaister, J. 1959. Le pistacher (Etude biblio graphigue). Fruits. 14:57–77.
- Mahmoodabadi, S.K., B. Panahi, J. Agharehimi, and A.R. Talaie. 2012. Determination of fatty acids, protein and amino acids in fruits of three pistachio (Pistacia vera L.) cultivars in Kerman Province, Iran. Plant Ecophysiol. 4(3):125–128.
- Okay, Y. 2002. The comparison of some pistachio cultivars regarding their fat, fatty acids and protein content. Gartenbauwissenschaft. 67(3):107–113.
- Özdemir, A. 2013. Bazı anaçların değişik Antep fıstığı çeşitlerinin fenolojik ve pomolojik özellikleri üzerine etkileri/Effects of some rootstocks on phenological and pomological features of different pistachio cultivars. Doctoral dissertation.
- Özrenk, K., I. Javidipour, T. Yarilgac, F. Balta, and M. Gündoğdu. 2012. Fatty acids, tocopherols, selenium and total carotene of pistachios (P. vera L.) from Diyarbakır (Southestern Türkiye) and walnuts (J. regia L.) from Erzincan (eastern Türkiye). Food Sci. Technol. Int. 18(1):55–62. doi: 10.1177/1082013211414174.
- Polari, J.J., L. Zhang, L. Ferguson, N.O. Maness, and S.C. Wang. 2019. Impact of microclimate on fatty acids and volatile terpenes in “kerman” and “golden hills” pistachio (pistacia vera) kernels. J. Food Sci. 84(7):1937–1942. doi: 10.1111/1750-3841.14654.
- Şahin, S. 2017. Effect of nanofiber barrier leaf fertilizer, nanotechnolocal calcite and kaolin applications on yiel and some quality characteristics of pistachio. Harran University Institute of Science and Technology, Şanlıurfa, Türkiye, Master Thesis.
- Sharifkhah, M., D. Bakhshi, M. Pourghayoumi, S. Abdi, and H. Hokmabadi. 2020. Effect of pollination time on yield and antioxidant properties of some pistachio cultivars. Int. J. Hortic. Sci. Technol. 7(1):51–58.
- Söğüt, N. 2016. Effects of promalin (GA4+7 + BA) applications on yield and some nut quality characteristics of pistachio. Harran University, Institute of Science and Technology, Şanlıurfa, Türkiye, 41, Masters Thesis.
- Spiegel-Roy, P., D. Mazigh, and M. Evenari. 1977. Response of pistachio to low soil moisture Conditions1. J. Am. Soc. Hortic. Sci. 102(4):470–473. doi: 10.21273/JASHS.102.4.470.
- Tekin, H. 1990, September. Comparison of existing pistachio varieties and selected hopeful types. Türkiye I. Pistachio Symposium (Proceedings), 11–12, Gaziantep, Türkiye.
- Tomás‐Barberán, F.A., and J.C. Espín. 2001. Phenolic compounds and related enzymes as determinants of quality in fruits and vegetables. J. Sci. Food Agric. 81(9):853–876. doi: 10.1002/jsfa.885.
- Tsantili, E., K. Konstantinidis, M.V. Christopoulos, and P.A. Roussos. 2011. Total phenolics and flavonoids and total antioxidant capacity in pistachio (Pistachia vera L.) nuts in relation to cultivars and storage conditions. Sci. Hortic. 129(4):694–701. doi: 10.1016/j.scienta.2011.05.020.
- Tunç, Y., M. Yaman, and K.U. Yilmaz. 2024a. Elucidating the genetic diversity in wild olive (Olea europaea L. subps. oleaster) genotypes from the Mesopotamia region with multivariate analyses. Genet. Resour. Crop Evol. 1–12. doi: 10.1007/s10722-024-01948-x.
- Tunç, Y., M. Yaman, Y.M. Keçe, K.U. Yilmaz, E. Yildiz, and A. Güneş. 2024b. Characterization of olive (Olea europaea L.) cultivars; colour properties, biochemical contents, antioxidant activity and nutrient contents. Genet. Resour. Crop Evol. 1–13. doi: 10.1007/s10722-024-01991-8.