Defense of cabbages against herbivore cutworm Spodoptera litura under Cd stress and insect herbivory stress simultaneously

• Published in: Environmental pollution (1987) 2024-10, Vol.358, p.124519, Article 124519
• Main Authors: Guo, Yeshan, Chen, Jin, Liao, Huimin, Wu, Kaixuan, Xiao, Zhenggao, Duan, Qijiao, Wang, Jianwu, Shu, Yinghua
• Format: Article
• Language: English
• Subjects: Animals; Brassica - chemistry; Cadmium; Cd stress; Herbivory; Herbivory stress; Larva - physiology; Phenols - metabolism; Plant Leaves - chemistry; Secondary metabolites; Soil Pollutants; Spodoptera - drug effects; Spodoptera - physiology; Spodoptera litura; Stress, Physiological; Volatile organic compounds; Volatile Organic Compounds - metabolism
• ISSN: 0269-7491; 1873-6424; 1873-6424
• DOI: 10.1016/j.envpol.2024.124519

Biotic (e.g., heavy metal) and abiotic stress (e.g., insect attack) can affect plant chemical defense, but little is known about the changes in plant defense when they occur concurrently. Herein, the impacts of heavy metal cadmium (Cd) stress and insect herbivory stress on the direct and indirect defense of two cultivar cabbages of Brassica campestris, the low-Cd cultivar Lvbao701 and the high-Cd cultivar Chicaixin No.4, against the herbivore cutworm Spodoptera litura were investigated. Although 10 mg kg−1 Cd stress alone inhibited leaf secondary metabolites (total phenolics, flavonoids), it reduced the feeding rate and odor selection of S. litura towards both cultivar cabbages, especially for Lvbao701, by increasing leaf Cd content and repellent volatile organic compounds (VOCs) (6-methyl-5-hepten-2-one, 7,9-di-tert-butyl-1-oxaspiro (4,5)deca-6,9-diene-2,8-dione), and reducing soluble sugar and attractive VOCs (3-methyl-3-pentanol, 2,5-hexanedione, tetradecanal). Under 2.5 mg kg−1 Cd and herbivory stress, although leaf total phenolics and flavonoids increased significantly, the feeding rate and odor selection of S. litura towards both cultivar cabbages increased, especially for Chicaixin No.4, indicating that the chemical defense of cabbages was depressed. Therefore, Cd stress alone improved the insect resistance of cabbages, whereas herbivory stress weakened the enhanced cabbages defence by Cd stress. The low-Cd cultivar Lvbao701 presented stronger insect resistance than Chicaixin No.4, suggesting that Lvbao701 application in Cd-polluted soil can not only decrease Cd transmission to higher levels in the food chain but also reduce pest occurrence. [Display omitted] •10 Mg kg−1 Cd stress alone enhanced cabbage resistance to Spodoptera litura larvae.•Herbivory stress and 2.5 mg kg−1 Cd stress weaken cabbage defense against S. ltirua.•Leaf Cd content negatively affected feeding rate of S. ltirua under Cd stress alone.•Leaf soluble sugar was the key to cabbage insect resistance under both stresses.•Low-Cd cultivar Lvbao701 plants present stronger insect resistance under Cd stress.