Effects of bud load on quality of Beogradska besemena and Thompson seedless table grapes and cultivar differentiation based on chemometrics of analytical indices.

BACKGROUND

The effects of bud load on the quality of Beogradska besemena and Thompson seedless table grape cultivars were studied. Two pruning treatments were imposed: 44 and 18 buds per vine for Beogradska besemena and 44 and 22 buds per vine for Thompson seedless.

RESULTS

In Beogradska besemena the reduction of bud load decreased titratable acidity (-4%), skin dry weight (-16%) and malic and citric acid contents (-43 and - 20%) and increased tartaric acid content (14%). The decrease in pulp antioxidant activity (-36%) was related to the decrease in hydroxycinnamoyl tartaric acid content (-13%). Concerning skin, the reduction of bud load decreased catechin and caffeoyl tartaric acid contents (-42 and - 40%) and significantly increased rutin and quercetin-3-O-glucopyranoside contents as specific compounds and flavonoids and proanthocyanidins (9 and 21%) as classes of compounds, thus causing an increase in antioxidant activity (6%). In Thompson seedless the reduction of bud load increased soluble solid content (7%), acidity (9%) and concentrations of the three organic acids (7, 3 and 14%). The increase in pulp antioxidant activity (25%) could be attributed to the increase in total phenolics (69%). The reduction of bud load caused a significant decrease in quercetin-3-O-glucopyranoside (-26%) and antioxidant activity (-15%) in skin. Principal component analysis allowed good separation between samples of the two cultivars, independently of bud level.

CONCLUSION

The results indicate that the effects of different bud loads are cultivar-dependent. Bud load and genotype differences were shown to dramatically impact the quality and antioxidant properties of table grape.