Effect of methyl jasmonate on hydroxamic acid content, protease activity, and bird cherry-oat aphid Rhopalosiphum padi (L.) probing behavior.

The concentration of hydroxamic acids increased in wheat seedlings exposed to methyl jasmonate. The proteins isolated from such seedlings inhibited trypsin activity. Free-moving aphids avoided plants that had been exposed to methyl jasmonate prior to the experiment. These aphids were able to reject such plants within 15 min, and the inclination to stay on control plants lasted at least 24 hr. Electronic recording (EPG) of aphid stylet activities showed a trend towards reduction in penetration time and total time of phloem sap ingestion on jasmonate-treated plants. However, the duration of the first period of feeding was similar on treated and control plants.