Effect of insect feeding, pathogen infection, and heat stress on antioxidant properties of wheat bran

Abstract

The potential of hard winter wheat (Triticum aestivum L) to produce antioxidant-rich crops has been considered as a value addition strategy to increase farm profitability, but the inherent variability in phenolics concentrations in wheat crops is a barrier. This problem also makes marketing the health-promoting benefits of whole wheat products difficult. Although some variability is explained by genetic diversity, a significant portion is owing to stress factors such as elevated temperatures, fungal attack, and insect damage. Limited information is available on formal trials designed to investigate these relationships. In this study, wheat (Triticum aestivum L) cultivar Karl 92 was stressed by bird-cherry oat aphid (Rho-palosiphum padi) feeding, leaf rust (Puccinia triticina) infection, and postanthesis high-tem-perature stress. Total phenolic content (TPC) and 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity (%DPPH) of the resulting wheat bran and those of nonstressed plants were measured. Plant fitness parameters such as the number of spikes and grain yield were also evaluated. Heat-stressed plants had the lowest number of spikes (P < 0.0151), shriveled kernels, and lowest TPC and %DPPH in wheat bran-free (P < 0.0633, P < 0.0048) and bound (P < 0.0003, P < 0.0009) phenolic extracts. Aphid feeding explained some of the variation in TPC (P < 0.0719) and %DPPH (P < 0.0038) of free phenolic extracts, so this stress factor has potential to produce antioxidant-rich wheat bran. Rust infection did not change the antioxidant concentration on the bran, but it showed potential to produce wheat crops with high phenolics per acreage due to high grain yield (P ≤ 0.0821).