Lotus japonicus infested with herbivorous mites emits volatile compounds that attract predatory mites

It is known that plants can defend themselves indirectly against herbivores by emitting volatile compounds that attract the herbivores' natural carniv orous enemies. To clarify whether or not Lotus japonicus has an indirect de fense mechanism against spider mites, Tetranychus urticae, we investigated the responses of predatory mites, Phytoseiulus persimilis, to volatile comp ounds released from T. urticae-infested L. japonicus in a Y-tube olfactomet er. Plants infested with spider mites attracted more P. persimilis than did clean air. Uninfested plants and artificially damaged plants did not attra ct P. persimilis. When infested by spider mites, L. japonicus plants starte d emitting (Z)-3-hexenyl acetate, (E)-4, 8-dimethyl-1, 3, 7-nonatriene, ger macrene d, 1-octen-3-ol and methyl salicylate (MeSA). These compounds were considered to be T. urticae-induced plant volatile compounds. When three L. japonicus mutants deficient in nodule organogenesis were infested by the s pider mites, they all attracted P. persimilis. However, two of the infested mutants emitted blends of induced volatile compounds that were qualitative ly different from those emitted from infested wild type L. japonicus.