Crab Apple (Malus spp.) Seed Tocopherol Profile: Impact of Genotype, Species, Purpose and Rootstock

Abstract

Apples are one of the most popular crops in the world, grown for fresh consumption, processing, and ornamental purposes. In the present study, the seeds of thirty crab apple (Malus spp.) genotypes were analyzed to evaluate the tocopherol composition and find a crop-specific profile. The mean proportion (%) of tocopherol (T) homologues (α, β, γ, and δ) was as follows: α-T (45.8%), β-T (21.8%), γ-T (24.3%), δ-T (8.1%) with a mean content of 22.41, 10.89, 12.35, and 4.08 mg/100 g dry weight, respectively. The coefficient of variation was higher in γ-T (0.748), δ-T (0.648) and β-T (0.540), and about two times lower for α-T (0.320). The total content of tocopherols varied much less in studied genotypes (coefficient of variation 0.164). α-T was the predominant tocopherol homologue in twenty-four genotypes (33.4–79.0%), while γ-T (36.4–64.9%) was the predominant in the remaining six studied genotypes. Principal component analysis identified six groups based on the tocopherol profile. Variety, purpose (ornamental vs. edible), and species appear to be associated with tocopherol profile. Most Malus sp., M. × prunifolia, and edible genotypes were located in two groups characterized by twice the content of α-T over β-T, and similar content of both (α-T and β-T), respectively. In both cases the sum of α-T and β-T constituted about 80% of total tocopherols. Significant correlations among tocopherol homologues were obtained: positive between α-T vs. β-T and γ-T vs. δ-T, and negative between α-T vs. γ-T, α-T vs. δ-T, and γ-T vs. β-T. These can be explained by the biosynthetic pathway of those lipophilic bioactive compounds.