Chemical Compounds and Biological Activity in Black Currant (Ribes nigrum L.) Berries Depending on Soil Temperature and Moisture

This study examined the effect of soil temperature and moisture of different soil cultivation systems-unmulched soil, sawdust mulch, and black foil mulch-on the sugar and acid profiles, levels of bioactive phenolic compounds, and antioxidant and cytotoxic activity in black currant (cv. 'Titania') berries. The higher soil temperature under black foil mulch at 0-30 cm depth and on the foil surface during fruit set and fruit maturation, as well as the higher soil moisture content, directly led to an increase in the accumulation of total sugars, invert sugars, and sucrose compared with the other two cultivation systems. On the other hand, moderate soil temperature and low soil moisture, as recorded on unmulched soil, favoured the accumulation of total phenolics and flavonoids in berries, whereas no difference was observed in the levels of condensed tannins or gallotannins between unmulched soil and sawdust mulch treatment. Mulching with sawdust, which resulted in a stable soil water regime and steadily low soil temperatures, promoted the synthesis of all other chemical parameters tested (fructose, glucose, total acids, pH, organic acids, ascorbic acid, antioxidant activity, and cytotoxic activity). There was no difference in total anthocyanin content among soil cultivation systems. The present results suggest that soil temperature and moisture have an important effect on plant metabolism and promote the synthesis and accumulation of chemical compounds and biological activity in the fruit, thus positively affecting the quality and commercial value of the fruit.