Volatile cues influence the response of Rhopalosiphum padi (Homoptera: Aphididae) to barley yellow dwarf virus-infected transgenic and untransformed wheat

The attractiveness of Barley yellow dwarf luteovirus (BYDV)-infected wheat plants to Rhopalosiphum padi L. was evaluated under laboratory conditions. Two untransformed wheat varieties, virus-susceptible Lambert and virus-tolerant Caldwell, and one transgenic wheat genotype (103.1J) derived from Lambert and expressing the BYDV coat protein gene, were tested in three bioassays. First, R. padi responses to BYDV-infected or noninfected Lambert and Caldwell were evaluated. Significantly more aphids settled Onto virus-infected than noninfected plants when aphids were able to contact the leaves. Second, aphid responses to headspace from virus-infected or noninfected Lambert and Caldwell were tested. Significantly more aphids congregated on screens above headspace of BYDV-infected plants than above headspace of noninfected plants of both varieties. Third, aphid responses to headspace from virus-infected or noninfected and sham-inoculated (exposed to nonviruliferous aphids) Lambert and 103.1J plants were examined. Significantly more aphids congregated on screens above BYDV-infected than above noninfected or sham-inoculated Lambert. No significant differences in R. padi preferences for headspace above BYDV-infected compared with noninfected or sham-inoculated 103.1J plants were observed. The concentration of volatiles extractable from whole plant headspace was greater on BYDV-infected Lambert than on BYDV-infected 103.1J, noninfected, or sham-inoculated plants of either genotype. This is the first report of volatile cues associated with BYDV infection in wheat plants influencing the behavior of the vector R. padi. Additionally, these findings show for the first time that transgenic virus resistance in wheat can indirectly influence the production of volatiles making virus-infected plants less attractive or arrestant to aphids than are infected untransformed plants.