Assessment of Fatty Acid Composition, Bioactive Compounds, and Mineral Composition in Hazelnut Genetic Resources: Implications for Nutritional Value and Breeding Programs

This study was carried out to determine the fatty acid composition, bioactive compounds, and mineral element content of standard hazelnut cultivars and accessions from the Eastern Black Sea region. A wide variation was determined in terms of the traits examined between hazelnut accessions and cultivars. Most of the accessions investigated had higher values of bioactive compounds, oleic acid, stearic acid, Na, and Ca than the standard cultivars. Among accessions investigated, S-1 had the highest total phenolics and antioxidants (557.3 mg/100 g and 0.53 mmol/100 g) while P-4 had the lowest (307.3 mg/100 g and 0.22 mmol/100 g). The highest oleic acid content was determined in P-2 (87.16%); the lowest was in H-1 (71.24%). Linoleic acid ranged from 4.35% (P-1) to 18.06% (H-1). P-2 (3349 mg/kg and 2464 mg/kg, respectively) had the highest K and P contents. The highest Mg content was found in S-1 (1787 mg/kg). The highest value of Ca and Na was determined in P-1 (2701 mg/kg and 412 mg/kg, respectively). Principal component analysis revealed that the traits studied could effectively explain the variability among hazelnut genetic sources. First, three components explained about 60% of total variation. PC1 was related to arachidonic acid and most of the mineral elements (P, K, Mg, Ca, Fe, Mn, Zn, Cu, B, Cd, Ni, and S), and explained 27.6% of the total variation. PC2 explained 18.3% of the total variation, and was mainly related to oleic, linoleic, and linolenic acid, as well as Ca. PC3 was related to total phenolics, total flavonoids, antioxidant activity, and palmitic acid, and explained 14.5% of total variation. The oleic acid had a strong negative correlation with linoleic acid (-0.99 ***) and linolenic acid (-0.95 ***). A strong positive correlation was determined between antioxidant activity and total flavonoids (r = 0.95 ***). K content showed a strong positive correlation with P (r = 0.92 ***) and Mg (r = 0.82 ***) contents. A strong positive correlation was also determined between P and Mg (r = 0.91***). These findings revealed that many of the accessions investigated were a good source of fatty acids and bioactive compounds. As a conclusion, most accessions with superior nutritional content can be evaluated as genetic material for the development of new cultivars in hazelnut breeding programs.