Clonal Selection of ‘Mincane’ Hazelnut cv: Physical Properties

This study was conducted to identify Mincane cv clones with superior physical traits in the Trabzon province, Maçka district, Esiroğlu region between 2014 and 2019. Selection research in the study area based on the study objective revealed 14 Mincane clones with superior traits. In these selected clones, yield, number of nuts per cluster, nut characteristics, kernel characteristics, nut weight, shell thickness, kernel weight, kernel percentage, shriveled kernel, kernel cavity, blank kernel, split suture, black - tipped kernel, picola nut, lemoning, sour lemon taste, tumor ratio, good kernel, defective kernel, fibrousness, bleaching ability, perforated nut traits, and sensory and color properties were investigated. Physical traits varied greatly within the Mincane cv, and this difference was statistically significant (P˂0.001). It was concluded that the G 1 , G 6 , G 4 , and G 11 clones were promising and that it would be useful to closely monitor the G 13 clone


Introduction
The hazelnut of the genus Corylus, which belongs to the birch (Betulaceae) family and grows as a shrub or small tree, is one of the most consumed hard-shelled fruits worldwide.Hazelnut is also one of the leading crops globally among nuts.The hazelnut has been grown in Anatolia since ancient times, and the Black Sea region of Turkey has the most suitable habitat for its cultivation.It is one of Turkey's most important export crops.The hazelnut production in Ordu, Giresun, Trabzon, Bolu, Sakarya, and Samsun, located in the Black Sea region, accounts for nearly 90% of Turkey's total.In the Black Sea region, summers are cool (23°C-24°C), winters are mild (5°C-7°C), heavy precipitation is observed, and the interior is generally characterized by a continental climate.The mountains that run parallel to the coast limit agricultural areas and influence the climate.In the Black Sea region, which has the greatest amount of rainfall in Turkey, the mountains prevent humidity from passing from the coastal areas to the interior districts, causing vegetation to differ (Öztürk and Serttaş, 2018;Turan and İslam, 2020).
Because of these climate characteristics, this region produces the world's highest quality hazelnuts.Aside from direct consumption, hazelnut is widely used in the food industry as an ingredient or as hazelnut oil.Hazelnut is a nutrient-rich food because of its high content of amino acids and fatty acids (Dönmez et al., 2016).It is important in human nutrition and health because of its composition of mono-and polyunsaturated oleic and linoleic fatty acids, sterols, essential minerals, free phenolic acids, phenolic compounds, and organic acids (Shafiei et al., 2020).In addition to being consumed as a snack, hazelnuts are widely used in the food industry as whole, chopped, or flour.In addition, the use of hazelnut oil is important in the food industry, and 80% of hazelnuts are processed in the production of chocolate; 15% in the confectionery, biscuit, and pastry industries; and 5% is consumed fresh without processing (Cansev et al., 2018).
Its antioxidants have anticancer and antiatherosclerotic properties, and phytochemicals and phenolic compounds protect against the harmful effects of cancer and oxidative stress (Yılmaz et al., 2019).The nutritional value of hazelnut varies based on cultivar, harvest season, drying method, clonal differences, nutrition, altitude, and habitat (Turan, 2018).However, it is well known that the most important factor is the genetic structure of the variety and/or clone (Turan, 2007;İslam, 2019).
Many characteristics distinguish economically valuable hazelnut varieties, including the number of nuts per cluster (NPC), nut and kernel weight, efficiency, shell thickness, bleaching ability (BA), shriveled kernel ratio, and split suture ratio.However, clones with high yield and industry-oriented superior quality traits are preferred for cultivar breeding.
To make this decision, the breeder must investigate and evaluate more than one factor affecting complex traits, such as yield, which are controlled by multiple genes.Accordingly, extensive research into the physiology of traits controlled by different genes is required.Thus, in selection breeding programs, it is critical to investigate correlations between different traits and their economic importance.A positive correlation between two or more traits enables the simultaneous breeding of multiple variants, while a negative correlation indicates the need for an association between desirable traits (İşbakan and Bostan, 2020).In addition, these quantitative characteristics can be greatly affected by environmental factors.In other words, they have the potential to be far more variable than single gene traits.Therefore, breeders must be knowledgeable about the causes of yield variability in various environmental conditions.Otherwise, all the work and effort will be in vain.
Numerous selection studies have been conducted since 1969 (İslam, 2000;Turan, 2007;Turan and Beyhan, 2009;Göğüs, 2015;Pekdemir, 2019;Şahin, 2019;Kan, 2019;İslam and Çayan, 2019), and breeding selection methods are still being researched in the agricultural field.Plant mutation and natural hybridization can cause a wide range of variation within a variety.Therefore, selecting clones with desired traits among the variations is critical for breeders (İslam, 2019).Because the novel variations may have a higher economic value than the source variety or vice versa, selection breeding studies are ongoing.
Unfortunately, most selection breeding studies have been conducted and are being conducted in extremely large areas and with a large number of materials.However, field studies have revealed that specific investigations into a limited area produce more significant results.In addition, most of these studies have similar selection criteria, and there are few studies with well-defined cultivar characteristics.
Hazelnuts are one of the most popular nuts because they are not only delicious but also high in calories.They can be consumed fresh or blanched.Hazelnuts are used in bakery products, confectionery, and chocolates as well as in some high-end products, such as chopped hazelnuts and hazelnut milk (Fan et al., 2020).Hazelnut oil, which is rich in high-quality unsaturated fatty acids, is used as a cooking oil with a yellow color and flavor (Matthaus et al., 2012).Aside from it being edible, hazelnut oil can be used to make soap, cosmetics, candles, and other household items (Alaşalvar et al., 2006).
Because the shape and size of the hazelnut affect the machine configuration used in the integrated facilities, the commercial identification of the shelled and kernel hazelnut varieties to be processed is based on physical characteristics known as morphological characteristics (Turan, 2007;Hosseinpour et al., 2013;Krol et al., 2020).However, statistical analysis based on genetic and/or metabolomic markers is considered a more appropriate method for obtaining a clear definition of hazelnut cultivars, taking into account their geographical origins (Ghisoni et al., 2020).
There are 20 standard hazelnut cultivars in Turkey, and variety registration trials are ongoing.
Except for newly registered varieties, all other varieties show significant variation, necessitating the continuation of selection studies.Selection of commercially produced Tombul, Foşa, and Palaz cultivars has started and is still ongoing.However, no selection studies have been conducted on the Mincane cv, which originates from Trabzon.When ongoing selection breeding studies for many years were examined, it was discovered that studies were conducted in a wide area with a large number of materials.This complicates and prolongs the selection of superior clones.With a large number of potential varieties in Turkey, a lack of completed selection studies, even in the Eastern Black Sea region, has a negative impact on the country's agricultural activities.It is critical to close this gap immediately and to conduct detailed studies in limited areas.Detailed studies in specific areas can reduce the likelihood of error ratio and material-based issues.
A comprehensive selection study was conducted in a limited area in the Trabzon province, Maçka district, Esiroğlu region.The present study aimed to select clones with superior characteristics by thoroughly examining all villages and neighborhoods around the valley.It has been concluded that the study data will lead to further research in the region and that the evaluation of the obtained clones will contribute significantly to the hazelnut industry.

Hazelnut samples
For the selection study, all villages in the region were examined and 14 hazelnut gardens with a size of at least 5 da that were not treated with chemical pesticides were selected (Table 1).During the selection process, technical staff from the District Directorate of Agriculture, agricultural consultants, headmen, villagers, and garden owners provided information and support.The study was conducted on three plants (branches) aged ~25 years from each orchard representing the selected hazelnut orchard.During the study period, ammonium nitrate fertilizer (5Ca (NO3)2NH4NO310H2O, CAN %26N) was observed to be used for top dressing (~50 kg/da) once a year in the middle of March; sucker shoots and weeds were pruned twice a year; and dried and old (>%50) branches were cut with no further application.These selected orchards have been studied for 5 years in terms of yield and resistance to diseases and pests.According to TGHB (2017), hazelnut orchards with regular yields and below the required threshold value for agricultural control against diseases (Xasthomanas coryline and phyllactinia guttata) and pests (Balaninus nucum L., xyleborus dispar, bud mite, and palemona prasina) were selected.Those clones with disease and/or pest detected above the threshold value were excluded from the ongoing study, and the study continued on the remaining material.
During the study, ~200 hazelnut orchards were examined in detail.The identification, marking, harvesting, and drying processes of the selected gardens were carried out according to Turan and Beyhan (2009).After drying, the samples were placed in a 1 kg paper bag and refrigerated at ~5°C and 60-65% relative humidity until the measurements were taken (Bosch KDN53NW22N A, No-Frost, Germany).

Physical measures: Shell and kernel traits
Yield: All three branches representing the orchard in the predetermined hazelnut orchards were harvested (~27.6% humidity), manually separated from the clusters (Turan, 2018), sun dried, and weighed on a scale with an accuracy of 0.001 g (Turan, 2021).The number of NPC was calculated by dividing the number of nuts per 100 randomly selected clusters from the harvested samples (Turan and Beyhan, 2009).The nut length, nut width, nut thickness, shape index, nut weight, kernel weight, kernel percentage, shell thickness, kernel cavity, blank nut, shriveled kernel,and good and defect kernel ratios were determined according to Turan (2019) and other traits according to Çetin et al. (2020).The color properties of the shell and kernels, including L (brightness), a (redness), and b (yellowness) values, were determined using the Hunter Lab Color Flex Ez color measurement device.
Before the measurements, the device was calibrated as X: 79.05, Y: 84.02, Z: 89.03, and L, a, and b values were determined by measuring from different points (Demir, 2018;Turan, 2021).The  2020).Sensory analysis was performed using the hedonic scale scoring test and consisted of 11 panelists in four different sessions (Şimşek, 2004).The panelists rated the hazelnuts from different orchards on a scale of 1-5 based on color, flavor, hardness, bitterness, foreign taste/smell, and overall evaluation.

Statistical analysis
Measurements were performed in triplicate on selected clones, and descriptive statistics were performed using SPSS v. 22.0 (Armok, New York: IBM Corp.).Statistical tests were conducted using SAS-JAMP v. 10.0 (SAS Institute Inc., Cary, North Carolina, USA).The difference between the results was determined at the P ˂ 0.05, P ˂ 0.01 and P ˂ 0.001 levels.

Results and Discussion
In breeding studies, yield is the most important selection criterion.First, the productive individual is selected, and then other physical and/or chemical properties are evaluated.Yield, on the contrary, causes an increase in the number of NPC, nut deformation and shrinkage, and a decrease in the shell thickness.Therefore, we believe that obtaining data that will not affect commercially standard fruit sizes would be appropriate.Otherwise, because branch thinning, which is widely used for other fruits, cannot be used for hazelnut clusters, the picola hazelnut ratio will increase and the standard value will deteriorate because of nut shrinkage.In our study, the highest yield was 519.56 g for the G1 clone, and the lowest yield was 304.45 g for the G8 clone (Table 1); the difference between them was statistically significant (P ˂ 0.001).
Many factors, such as variety, nutrition, yield, habitat, and harvest season, affect nut size (Xu and Hanna, 2010;Ercişli et al., 2011;Turan, 2017;Turan and İslam, 2019).It is also known that the heritability of nut length, girth, and thickness is high (h 2 = 0.68, 0.78, and 0.89, respectively) (Yao and Mehlenbacher, 2000).A high heritability indicates that they are less affected by environmental conditions.However, yield in hazelnuts is regarded as one of the most important factors influencing nut size.In addition, physical differences are observed even among nuts in a single cluster (Turan, 2017).During high-yielding seasons, the number of NPC and efficiency increase, while nut size and shell thickness decrease.An increase in the number of NPC causes a change in the shape value of the nut.Even within a single variety, differences in the physical properties of the fruit can appear year to year.
The number of NPC has a direct impact on the size and shape of the nut, so the ideal number is four pieces per cluster.As the number of NPC increases, the size of the nuts decreases, and they exert pressure on each other, causing shape variability and/or deformation.On the contrary, a low number of NPC has an effect on fruit size and shell thickness, and ultimately, fruit standard.(Turan, 2021).
Considering the abovementioned factors, all values were deemed acceptable because the number of nuts in all selected clones was 3-5 pieces per cluster.
No statistical difference was observed in or nut and kernel weight (P ˃ 0.05), but the difference in other traits was significant (P ˂ 0.001).This difference was considered normal as it fell within the range of values determined in previous studies.(Turan, 2007;Turan and Beyhan, 2009;Turan, 2019;Turan, 2021).Clones that were found to be above and below the standard during selection and research were excluded from the evaluation, resulting in values that fell within a certain range.
All shell and kernel shape index values were greater than one (1; Table 2).A slight upward trend has been observed.However, all of the determined values were less than 1.4, which is accepted as the index value of the Sivri cv (Köksal, 2018).Accordingly, we reported that all selected clones exhibited characteristics of round hazelnut varieties.It has been determined that the other shape index values usually have additional and general class ı traits (Table 2).Although the difference in nut and kernel weight values was statistically insignificant (P ˃ 0.05), measurements ranged from 1.69 to 2.00g and from 0.90 to 1.10 g, respectively.The economic importance of the kernel nut is greater because it is the part that is processed for export and/or fresh consumption.In this regard, it was concluded that the G13 clone exhibited better results in terms of nut weight, especially kernel weight.The kernel ratio appears to be an overrated characteristic.The hazelnut market considers this trait to be equal to or even superior to variety variations.Is high efficiency a desirable trait because pricing is done with more than 50% efficiency?Or why is the Uzunmusa cv, which has the highest yield, not considered the highest quality hazelnut?The features that distinguish hazelnut varieties and make them valuable are regular yield and standard-sized nut formation.In contrast, high kernel fullness causes stress when crushing because of the reduced space between the hard shell and kernel.
Therefore, an efficiency value of 50%-54% would be preferable.The belief that the hazelnut with the highest efficiency has the best quality is incorrect.The chemical composition of the hazelnut as well as the cracking and processing operations causing the least amount of damage are essential.
Increased damage and/or defective kernel ratio is not preferred by the hazelnut industry because it increases the costs.In the present study, the G12 clone had the lowest efficiency (47.12%), and the G6 clone had the highest efficiency (58.81%) (Table 2), with the G3-6 and G13 clones having superior values.Data represent the mean ± SD (n=3).Significant level; *, **, *** and "ns" mean significance at p˂ 0.05, 0.01, 0.001 and "not significant", respectively, among clones.
The average shell thickness of hazelnuts is 1 mm, with values well above 1 mm considered a thick shell.Therefore, a shell thickness of less than 1 mm is considered suitable for market use (Turan, 2021).According to our study, the shell thickness was approximately 1 mm.The G11 clone had the lowest value, which distinguished it from other clones.Except for the G3 clone, which has a shell thickness of 1.25 mm, it can be concluded that the clones are at an acceptable level.
The kernel cavity is an unstable trait that varies among varieties (Turan, 2007).In addition, the size of the internal cavity differs between the nuts within a single cluster based on the size of the nuts (Turan, 2021).No clones that differed or were severely defective in terms of this nut trait were found in our study.
In studies on pistachios, harvest season, irrigation status, plant nutrition, pruning, and rootstock have all been found to be effective on split sutures (Ertürk et al., 2015).In addition, it has been stated that splitting is a trait of variety and has a low incidence in domestic varieties (Özçağıran et al., 2005).
Among the other hard-shelled nuts, the heritability of this trait has been reported to be h 2 =0.48 in chestnut (Nishio et al., 2014).There have only been a few studies on the splitting trait of hazelnut.
However, it is known that this trait is frequently observed in some cultivars.Split sutures have been found in both filled and poorly filled hazelnuts.It has been proposed that a hazelnut's genetic structure may contain such a trait.A high ratio of this trait is undesirable because it causes an increase in the black-tipped kernel ratio in hazelnuts.Black tips on kernels have been linked to nuts with split or weak sutures (Turan, 2007;Turan, 2017), implying that an increase in the split suture ratio affects the black-tipped kernel ratio.Therefore, clones with split sutures in the orchard were excluded during the first stage of selection.
Hazelnuts with a nut size of less than 9 mm are classified as "picola" (small hazelnuts) (Fiskobirlik, 2004) and are generally not offered to the market; they are threshed and consumed as a snack.A high picola ratio is undesirable because it is unsuitable for industrial processing, leading to a cost increase.However, after bleaching, it is regarded as the class with the highest price range.
Higher sale prices may be implemented because more labor is needed during the bleaching process.
Moreover, it is valuable as a snack because it has superior taste properties compared to plump nuts.
The lowest value was found in the G4 and G11 clones (1.59%), and the highest value was detected in the G6 (9.43%) and G12 clones (9.86%).It would be better not to select these two clones with the highest value.Although picola hazelnut is a popular snack, it is not preferred because of increased costs and a lower nut standard.Currently, its consumption is uncommon, but if it becomes widespread and highly preferred in the market, clones with superior picola ratios may be evaluated.Blanched hazelnuts are unavailable in the domestic market owing to their high price.Because picola hazelnuts are more expensive, it is expected that consumption will be limited among the general population.
A low shriveled kernel ratio is preferred because it reduces BA and efficiency.Besides nut size, it is generally accepted that the most important traits affecting price are the BA and market efficiency value.In addition to variety, pricing is based mainly on commercial BA and a 50% yield in hazelnut purchases.Furthermore, shriveled kernel is influenced by many factors, such as soil structure, altitude, early harvest, clonal difference, variety, and climate (Turan andBeyhan, 2009, Kalkışım et al., 2016).The highest shriveled kernel ratio was observed in the G13 clone (2.08%) and the lowest in the G7 (0.33%) clone (Table 2).When other studies were examined (Turan, 2007;Turan and Beyhan, 2009;Turan, 2017;Turan, 2019;Turan, 2021), it was found that even the highest value in our study was very low compared to previous studies.It was assumed that a population with a higher shriveled kernel ratio as a nut trait had been detected.
The hazelnut worm (Curculio nucum) is known to be the most important pest in the hazelnut production areas worldwide (Saruhan and Tuncer, 2010;Saruhan et al., 2010).Saruhan and Şen (2016) stated that the damage caused by hazelnut worms varies according to the cultivar, and this damage varies in varieties such as Mincane (4.57%), Sivri (3.81%), Palaz (2.80%), Çakıldak (2.80%), Tombul (2.77%), and Karafındık (2.48%).Even the highest value of 1.03% (G9) obtained in our study was well below the previous data.These data show that the search method used in the orchard selection processes at the selection stage is appropriate.In the present study, orchards that were determined to be above the threshold value were excluded in the first stage, and orchards free of agricultural pesticides were selected.As a result, it can be predicted that the selected clones are less damaged and/or resistant to hazelnut worm damage compared to the eliminated clones and other studies.
Lemoning is defined as the formation of a dark yellow color around the part of hazelnut kernels that begins to deteriorate due to oil oxidation (Fiskobirlik, 2004;Turan, 2018).Sour lemon hazelnut kernels are defined as hazelnut kernels with distorted taste, color, and odor that leave a slightly sour taste and burn the mouth due to oxidized fat (Turan, 2017).Both traits appear after an insect sucks the kernel nut, and they develop depending on the cultivar practices.The lowest lemoning and sour lemon values were observed in the G13 (1.69%-2.72%,respectively) clone; the highest lemoning was recorded in the G1 clone (12.333%); and the highest sour lemon value was recorded in the G2 clone (18.22%).The amount of oil oxidation that occurs during lemoning varies depending on the variety (Turan, 2019;Turan, 2021).Hazelnut varieties high in unsaturated fatty acids are also more sensitive to fat oxidation (Turan et al., 2022).As a result, it was observed that the G13 clone was superior to the others in this trait.
Because the type of "stained kernel" damage caused by the green skunk cannot be distinguished by the external appearance, the producer is free to sell these products.No effort was made to mitigate this damage.However, the impact of "stained kernel" on hazelnut exports is critical.Stained kernel damage deteriorates the taste and appearance of the product, causing problems especially during the chocolate production process and when used as nuts (Saruhan and Tuncer 2010;Turan, 2021).
Therefore, low or no damage is desired.No kernel tumor damage was detected in G5-G11 clones, whereas the highest value of 3.37% was recorded in the G13 clone.
The increase in the fiber ratio caused a decrease in the BA of hazelnut.Therefore, it is preferred that the hazelnut kernels are fiber-free or have a low fiber content (Turan, 2007).In the present study, the lowest fiber ratio was detected in G10-G13 clones (9; fiber-free), while the highest fiber ratio was detected in the G4 clone with the lowest score (5; moderate) (Table 2).Although Turkish hazelnut varieties vary in terms of fiber content (Turan, 2007), it is known that the Mincane hazelnut variety is generally fiber-free (Köksal, 2018).
The good kernel ratio is influenced by many features, including variety, soil characteristics, cultivar practices, and some nut defects with high heritability (Turan, 2017).Mehlenbacher et al. (1993) reported that the heritability of the good kernel ratio was h 2 =0.415.This feature also varies from year to year (Turan, 2019).The highest plump kernel ratio was detected in the G4 clone, which also has the lowest defective kernel ratio (Table 2).The lowest good kernel ratio was found in the G8 clone (62.27%).Commercially, the highest good kernel ratio was preferred because it reduced production costs.Clones with a higher defective kernel ratio should be eliminated.
High BA is one of the main traits sought in products to be exported (Turan, 2017;Turan, 2019;Turan, 2021).It is reported that the heritability of BA, which is affected by many factors such as soil structure, habitat, and variety, is h 2 = 0.64 (Yao and Mehlenbacher, 2000).The highest BA was observed in the G11 clone (99.37%), and this value was higher than that of the Tombul cv (Turan, 2007).Therefore, the G11 clone must be evaluated and preserved.The sensory analysis and general evaluation showed that the G6 (4.33), G9 (4.00), and G14 (4.00) clones have higher scores.
The L value was high in clones G1 (39.26) and G13 (39.30) for the nut and in clones G11 (40.85) and G12 (40.24) for the kernel (Table 3).When the chroma values of the clones were evaluated, the most vivid colors were recorded in clones G6-G13 (7.22) for the nut and in clones G3 (10.27) and G12 (9.94) for the kernel.Therefore, it can be concluded that these clones are brighter in color.However, it should be noted that this color change is related to post-harvest applications, especially harvest season and drying method (Turan, 2018).Hazelnuts that are harvested early and exposed to precipitation during drying lose their brightness and become dull.Harvesting should be done Data represent the mean ± SD (n=3).Significant level; *, **, *** and "ns" mean significance at p˂ 0.05, 0.01, 0.001 and "not significant", respectively, among clones.

Conclusions and Recommendations
The study is the first selection study in the literature to investigate the physical traits of the Mincane cv in detail.It is also the first academic study of hazelnuts in this region.The study found a statistically significant difference among clones (P ˂ 0.001).There were significant differences in traits among clones, including yield in G1 (519.56 g/plant), efficiency in G6 (58.81%), shell thickness in G11 (0.91 mm), low picola hazelnut ratio in G4-G11 (1.59%), high good and low defective kernel ratio in G4 (85.35%), and high BA in G11 (99.37%) clones.As a result of this study, indicated that G1, G6, G4, and G11 clones are promising for hazelnut production.

Acknowledgements
The author wishes to thank Assoc.Prof. Fatih ÖNER for the statistical analysis.

Statement of Research and Publication Ethics
The author declares that this study complies with Research and Publication Ethics.
brightness or darkness of the color is represented by L, and its numerical value varies between 0 and 100.The color darkens as it gets closer to 0 and brightens as it gets closer to 100.The redness or greenness value of the color is represented by a, and a indicates redness in positive values and greenness in negative values.The yellowness or blueness value is represented by b.Similarly, when b has a positive value, the yellowness of the color dominates, and when b has a negative value, the blueness of the color dominates.Chroma (C) is related to the dominant pastel or vivid tone in the color.As the numerical value of the chroma increases, the vividness of the color increases.On the contrary, as the numerical value of the chroma decreases, the pastel tone dominates the color.Hue angle (α°) represents the angle corresponding to the dominant color of the product(Alibaş et al.,

Table 1 .
Sample codification, altitude and location of hazelnut clones

Table 3 .
Sensory analyzes and colour parameters of Mincane (cv) hazelnut clones