Abstract:

Application of exogenous chemicals and feeding of insect pests can induce wheat to produce various defense responses, such as changing in the composition of volatiles and contents of other secondary metabolites, which in turn will affect the behavior of phytophagous insects and their natural enemies. The concentration of DIMBOA (2,4-dihydroxy-7-methoxy-1,4(2H)-benzoxazin-3-one) increased in wheat seedlings after jasmonic acid (JA) or chitin solution was sprayed, but no change of DIMBOA concentration was found in the wheat treated with methyl jasmonate. Application of JA and feeding on the wheat by the wheat aphid, Sitobion avenae (F.) and the oriental armyworm, Mythimna separata (Walker) could induce the change of volatile profiles in wheat seedlings. The volatiles emitted from JA-applied plants could attract the parasitoid, Microplitis tuberculifer Wesmael, one of the natural enemies of the oriental armyworm. Furthermore, when they were feeding on the wheat sprayed with JA, the development and weight of the wheat aphids and oriental armyworms were restrained significantly, and the fecundity of the wheat aphids decreased significantly. The results indicated that application of JA in wheat seedlings can induce wheat to produce both direct defenses and indirect defenses by emitting specific blends of volatiles that attract natural enemies.

Key words: Wheat, jasmonic acid, Sitobion avenae, Mythimna separata, induced resistance, volatiles, DIMBOA