Variation and heritability of antioxidant activity and its relationship to anthocyanin content and total phenolic content in blueberry (Vaccinium subgenus Cyanococcus)

Dietary antioxidants may help prevent chronic diseases resulting from free radical oxidation. Fresh blueberry (Vaccinium L. sp.) fruit is an excellent source of antioxidants, due to high levels of anthocyanins and other phenolic compounds. Antioxidant activity (AA) may be increased further through breeding, if heritable variation is available. Variation in AA, total phenolic content (TPH) and anthocyanin content (ACY) was examined in 1998 and 1999 in fruit extracts of 52 genotypes from six species groups in the blueberry breeding population at the University of Minnesota. Genotypes varied for AA, TPH, and ACY in single and combined years, regardless of adjustment for berry size. Mean AA, TPH and ACY did not change between years but genotype x year interactions were observed for all traits. Total phenolic content and ACY correlated positively with AA. Vaccinium myrtilloides and V. constablaei/V. ashei hybrids ranked highest among groups for AA. V. corymbosum, V. angustifolium, and V. corymbosum/V. angustifolium hybrid groups were indistinguishable from each other. Variation in AA, TPH and ACY among nine cultivars grown in Minnesota (MN), Michigan (MI), and Oregon (OR) was observed within and over locations. Mean AA changed between years in OR and in MI. Cultivar x year interactions for AA, TPH, and ACY were observed within each location and for TPH and ACY between pairs of locations. Correlation for AA was high between MN and OR. Combined-year, narrow-sense heritability estimates, based on 20 crosses grown in MN, ranged from 0.43 to 0.56 for AA, TPH and ACY. Eighteen of 200 offspring were transgressive segregants for AA. Variation within families was larger than variation among families. Among nine cultivars grown in MI, cultivar-dependent increases in AA, TPH, and ACY occurred in mature berries during the first three weeks of storage at 5°C. In cultivar Elliott, the level of bush ripeness at harvest had no effect on AA, TPH or ACY, while fruit maturity at harvest and bush ripeness x fruit maturity interactions were significant. Berries harvested with 50% to 75% blue color demonstrated increases in AA, TPH, and ACY during storage.