Drought stress affects nutritional and bioactive compounds in potatoes (Solanum tuberosum L.) relevant to human health

Abstract

Background: Potatoes react very sensitively to drought during growth. Thus, appropriate plant stress responses may affect metabolites associated with the health quality of tubers. Objective: The aim of this study was to determine the effects of drought stress (DS) on soluble sugars, starch, crude protein, minerals, free amino acids (AAs), and fatty acids (FAs). Design: The experiment was carried out on three potato genotypes during two years with four replications. The plants were grown in pots in a glasshouse with optimal water supply and under drought stress conditions. After harvest, the tubers of these two variants were analyzed for nutritional and bioactive compounds relevant to human health. Results: Apart from genotypic differences in most parameters, the results revealed that the DS caused a decline in glucose and fructose (P < 0.05, all) in both years, while sucrose was increased, especially in the second year with severe stress (P < 0.01). Starch was significantly reduced by moderate stress in the first year (P < 0.01), but less affected in the second year. Crude proteins and total amounts of free amino acids (AAs) were clearly enhanced by the stress in both years (P < 0.05, all). The minerals magnesium (Mg), potassium (K) and phosphorus (P) (P < 0.05, all) were similarly enhanced, while calcium (Ca) actually declined (P < 0.05). The portion of α-linolenic acid (ALA) on total lipids was elevated in the stress variants (P < 0.01), while oleic acid (OLA), its precursor, decreased significantly (P < 0.05), but only in the first year. In the second year, ALA was generally higher and not further induced by the stress. Additionally, OLA was less affected in that year, which was similar to all the other FAs in both years. Interestingly, Myo-inositol (MI) and lipid acyl hydrolases (LAH) associated with modulation in cell membrane lipids were raised by the drought stress in each year (P < 0.01, all). In the second year, MI and LAH data of the drought stressed tubers correlated significantly (r = 0.90, P < 0.01), suggesting their joined action within plant stress responses. Conclusions: The biochemical changes induced by DS are not alarming with regards to human health. Decline in glucose, fructose, and starch, in addition to increase in crude proteins, free AAs, ALA, MI, and minerals like Mg, K and P is profitable for the health benefits of tubers. However, a better quality is associated with a decrease in tuber yield.