Variability in tocopherol concentrations in almond oil and its use as a selection criterion in almond breeding

Due to the importance of tocopherols for oil stability, and consequently in almond (Prunus amygdalus Batsch) kernel quality, the concentration of the three isomers alpha, gamma- and delta-tocopherol were determined over 2 years in oil from the kernels of a group of almond selections in five progenies obtained from crosses between eight parents. Oil content was highly variable between genotypes, ranging from 40-65% of the total kernel dry weight (DW), but was consistent over the 2 years. High variability in the concentrations of the three isomers, and of the total amount of tocopherol, were also observed, even among genotypes in the same progeny, with significant differences between progenies and individuals. In some genotypes, a significant year effect was observed, with higher concentrations in the first year, probably due to higher Summer temperatures. The concentration in alpha-tocopherol, the isomer with the major stabilising activity, was ten-times higher than the levels of gamma- and delta-tocopherol, which were similar. A significant and positive correlation was also found between the concentrations of alpha- and gamma-tocopherol. Tocopherol concentration was high in 'Marcona', a traditional high-quality Spanish cultivar, and in several late-blooming selections. The continuous distribution of tocopherol concentrations suggests polygenic control. Significant differences in concentrations of alpha- and gamma-tocopherol indicate that high tocopherol concentration is a clearly attainable objective in almond breeding.