P. Dvořák

Impact of Phenolic Content on Antioxidant Activity in Yellow and Purple-fleshed Potatoes Grown in the Czech Republic

ABSTRACT Purple-fleshed potatoes cultivars are new on the Czech market. Intensive trials about growing purple-fleshed potato cultivars in the Czech Republic are currently being carried out. Recently many articles deal with phenolic antioxidants and their contribution to the human health; thus the aim of this study was to determine the differences in total phenolic (TP) content and antioxidant activity (AA) between yellow (cvs. Impala, Karin, Dita, Saturna) and purple-fleshed (cvs. Valfi, Violette) potatoes grown in the Czech Republic in 2004 in four locations in field trials. TP content was determined by Folin-Ciocalteau assay and AA by DPPH assay both in freeze-dried tuber matter. Results showed a statistical significant difference in TP content and AA between yellow- and purple-fleshed potatoes. Purple-fleshed cultivars showed 60% higher TP content than yellow-fleshed cultivars and AA content was double in purple-fleshed cultivars. A significant linear correlation between TP and AA was found (r2 = 0.747). Average TP content in yellow-fleshed cultivars was 2.96 GAE (gallic acid mg g−l DM) and in purple-fleshed cultivars 4.68 GAE was found. Average AA in yellow-fleshed cultivars was 11.26 AAE (ascorbic acid equivalent mg 100 g−1 DM) and in purple-fleshed cvs. 24.79 AAE. Purple-fleshed potatoes showed a lower variation among localities (6 % only). The results showed that AA of freeze-dried tuber matter is very low when compared to other plants or sources (wine, tea, chocolate and blueberries) although a high potato intake in humans by Czechs (72 kg capita−1 year−1) is considered.

Potatoes (Solanum tuberosum L.)

In the area of potato production, targeted research solving concrete and actual problems of potato producers runs on Czech University of Life Sciences in Prague. In the last few years, we were focused on the production of new potatoes designated for early harvest, and we were focused on capitalization of yielding and qualitative characteristics of colored potato variety. These findings were further utilized and transferred to the system of organic farming. Firstly, we watched the influence of organic farming on yield and quality of tubers. Ecological ways of cultivation had strong negative influences on yield (decrease of 36%). From qualitative characteristics, organic farming increased the content of polyphenols by 10.2%, decreased the content of nitrates by 11.0%, and decreased the content of reducing sugars by 22.0%. We also evaluated the possibilities and impacts of mulch on potato cultivation. The mulch on top of ridges affected the temperature of soil (it increased the temperature by 0.2–0.6 °C under black mulching nonwoven fabric, and it decreased by 0.5–0.8 °C under herbal mulch). The mulch also affected soil humidity (herbal mulch decreased the soil humidity) and adjust weed infestation (20 to 92% lower), soil erosion (95% lower), the occurrence of Colorado beetle (the number of larvae was 22.8% lower with herbal mulch and 88.7% higher with mulching textile), and late blight in potato vegetation.

Stimulation sorghum seed leading to enlargement of optimum conditions during germination and emergence

The ways to improve the vitality of sorghum seed after treatment with Lexin and M-Sunagreen were tested in laboratory conditions. These methods of seed stimulation were also tested in field conditions. All experiments were carried out in 2011–2013. Positive results after using the presented formulations for testing of germination were observed not only in laboratory conditions but also in field experiments. Seeds stimulated by Lexin reached statistically higher germination (95%) compared to control (91.5%) with the shortest medium time of germination (3.5 days) versus control seeds (4.3 days). Higher, faster and smoother germination of stimulated seeds resulted in higher average number of plants per m2 (about 2.1 plants/1 m2 in Lexin compared to control seeds) and thereby contributed to higher average yields up to two tons of dry matter per hectare.