Effect of water stress on glucosinolate content of Brassica carinata and performance of Brevicoryne brassicae and Myzus persicae

Abstract

Drought-related changes in plant chemical composition affect plant resistance to insect herbivores. Ethiopian mustard (Gomenzer) Brassica carinata (A) Braun var. Yellow Dodolla was grown under three different water treatments; drought-stressed, well-watered and water-logged conditions to evaluate glucosinolate content and performance of two aphid species, the generalist Myzus persicae (Sulzer) and specialist Brevicoryne brassicae (L.). The analysis of High Performance Liquid Chromatography showed that water stress altered the levels of glucosinolates in (B) carinata plants. Plants cultivated under water-logged showed significantly higher glucosinolate content (2.236 µmol/g) when compared to well-watered (1.307 µmol/g) plants, whereas plants grown under drought-stressed (0.773 µmol/g) showed significantly reduced glucosinolate content after two week stress. B. carinata plants grown under water-logged condition had significantly higher sugar level (785.8 µg/g) followed by well-watered (667.6 µg/g) and drought-stressed (637.9 µg/g) plants after two week stress. Both aphid species reacted differently to water stress-induced change in the host plants. Significantly higher number of B. brassicae was recorded on plants grown under drought-stressed (395 aphids) plants than well-watered (278 aphids) and water-logged plants (179 aphids). Populations of M. persicae were significantly larger on plants grown under water-logged (558 aphids) and followed by well-watered (329 aphids) and drought-stressed plants (193 aphids). Feeding by both aphid B. brassicae and M. persicae increased significantly the level of glucosinolates in B. carinata plants. B. brassicae induced higher amount of glucosinolate content (3.85 µmol/g) when feeding on drought-stressed plants whereas M. persicae induced higher glucosinolate content (3.55 µmol/g) on water-logged plants. Water stressed B. carinata plants resulted to lower glucosinolate content and higher aphid population.