Short communicationEffect on health promoting phytochemicals following seaweed application, in potato and onion crops grown under a low input agricultural system
Introduction
Seaweed extracts are biostimulants that have been traditionally used as soil conditioners in improving plant growth in agricultural crops (Hurtado et al., 2009). Numerous studies have revealed the benefits of seaweed extracts on plants including early seed germination, improved crop performance and yield, enhanced shelf life and better resistance to biotic and abiotic stress (Eyras et al., 2008, Jayaraman et al., 2011). Seaweed extracts have also been shown to improve the phytochemical content in plants, this is due to an increase in the concentration of bioactive molecules including antioxidants in the treated plants (Fan et al., 2011). In recent years, more consideration is being given to bioactive compounds that play a vital role in growth and development of plants as well as the protective benefits they offer in chronic diseases such as cancer and cardiovascular diseases (Chu et al., 2002, Picchi et al., 2012). Phenolic compounds are a group of polyphenols, and can be found in many fruits and vegetables. They are predominant in potatoes, accounting for 80–90% of the total phenolic content (Brown, 2005). Flavonols are another group of polyphenols that can be found in many fruits and vegetables, with onions being a rich source of these compounds (Hollman and Arts, 2000).
There is very little information about the influence of seaweed extracts on health promoting compounds and nutrition value of onions and potato treated with seaweed. The objective of this study was to investigate the effect of seaweed extract (Ascophyllum nodosum) application on the phytochemical content in low input production systems on onion and potato. We report preliminary results of two different experiments on the effect of a cold process seaweed extract Algae Green™ on the phytochemical content and yield of onion and potato, evaluating different products, application rates and methods.
Section snippets
Onion
In the first experiment, onion seeds (cv Hybing F1) were placed in cell trays (23 mm × 23 mm × 35 mm) containing potting mix (Shamrock compost) and sown at 1.5 cm deep. Cell trays were placed in a unheated greenhouse (approximately 20–22 °C) and were grown for 7–10 weeks prior to planting in the field. The experiment was conducted at a site in Kinsealy (53° 25 N Lat 6 10 W), located in north county Dublin, Ireland. Soil type was characterised as loam to clay loam belonging to the grey brown podzolic soil
Statistical analysis
All data are expressed as mean ± standard deviation unless otherwise stated. Data were analysed using Friedman's non parametric test (R statistical package). A significant difference was considered at the level of P < 0.05 or P < 0.01.
Total phenolics
In the onion crop statistically significant differences were recorded in total phenolic content (Friedman, df = 4, <0.01). Seaweed treated plants had a higher phenolic content relative to the control (Fig. 1). There were also significant differences between the 5 L/ha and the 3 L/ha rate. In the potato trial no statistically significant differences were recorded in total phenolic content (Friedman, df = 3, P < 0.11), although the seaweed treated plants had a higher concentration in phenolics (Fig. 2).
Total flavonoids
Discussion
Phytochemical compounds have been linked with the inhibition of certain types of cancer (Simon, 2002). It has been proposed that seaweed extracts are promising compounds for providing both novel biologically active substances and essential compounds for human nutrition, with high potentially economical impact in food and pharmaceutical industry and public health (Jimenez-Escrig et al., 2012). Consequently, understanding the effect of seaweed extracts on the phytochemical profile of vegetables
Conclusions
The preliminary data presented in this paper, although from a small number of replications, provides evidence that repeated application of cold process seaweed extracts. Either liquid or dry can significantly increase the amount of phytochemicals in plants. These findings are very encouraging, as they may offer a possible way to increase health promoting phytochemicals in vegetables without the need of costly breeding programmes.
Acknowledgements
The research was financially supported by IRCSET and OGT through the IRCSET enterprise postdoctoral fellowship scheme. We thank Leo Finn and Christopher Roberts for their assistance with the trials.
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