2.2 Aphid Infestation.
Aphid (Sitobion avenae ) was provided by Dunlun Song, College of Plant Protection, China Agricultural University. The aphids were kept in the compartment with the relative humidity at 50%~70%, temperature at 18~25℃, and the light intensity of 80 µmol m-2 s-1. The nano-Se was applied in the wheat seeding stage. Ten adults of apterous S. avenae were then inoculated on wheat leaves after two days. Nano-Se was sprayed every 7 days and used 3 times at all. Aphid numbers were counted every 5 days after the inoculation (only adults were counted). All experiments were carried out on 120 mesh nylon mesh (75 × 75 ×75 cm), and there were five nylon meshes in total. Each nylon mesh had four different treatments (control, Se1, Se5, and Se20) with five replicates. The whole test lasted for one month. The aphid was removed from the wheat leaves and collected the wheat seedlings in liquid nitrogen. The samples were stored at -80℃ before measurement for antioxidant enzymes and gene expression.