Volatile Cues Influence the Response of Rhopalosiphum padi (Homoptera: Aphididae) to Barley Yellow Dwarf Virus–Infected Transgenic and Untransformed Wheat (original) (raw)

2004, Environmental Entomology

The attractiveness of Barley yellow dwarf luteovirus (BYDV)Ðinfected 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. SigniÞcantly 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. SigniÞcantly 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. SigniÞcantly more aphids congregated on screens above BYDV-infected than above noninfected or sham-inoculated Lambert. No signiÞcant 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 Þrst report of volatile cues associated with BYDV infection in wheat plants inßuencing the behavior of the vector R. padi. Additionally, these Þndings show for the Þrst time that transgenic virus resistance in wheat can indirectly inßuence the production of volatiles making virus-infected plants less attractive or arrestant to aphids than are infected untransformed plants. KEY WORDS virus-induced volatiles, virus vectors, insect behavior, host plant resistance, coat proteinÐmediated resistance THE BIRD CHERRY-OAT APHID, Rhopalosiphum padi L., is one of the most serious insect pests of cereals worldwide and one of the main vectors of Barley yellow dwarf virus (BYDV) (Gildow and Rochow 1983). In Idaho, R. padi is one of the most numerous and economically important aphids on winter and spring wheat, Triticum aestivum L. (Forster and Rochow 1983, Bishop and Sandvol 1984, Schotzko and Bosque-Pé rez 2000), damaging hosts both by direct feeding and by transmitting BYDV (Stern 1967). BYDV is a member of the family Luteoviridae, genus Luteovirus (van Regenmortel et al. 2000), and is transmitted in a persistent-circulative manner by R. padi and 25 other aphid species in North America (Halbert and Voegtlin 1995). BYDV disease involves a complex interaction between plant, virus, and aphid vectors (Irwin and Tresh 1990). Virus-infected plants have been shown to affect the biology of aphid vectors (Macias and Mink 1969, Ajayi and Dewar 1983, Blua and Perring 1992, Eckel and Lampert 1996). Most of the available literature suggests that plants infected with virus are more favorable to insect vectors than their healthy counterparts, decreasing their developmental periods and increasing their growth rates, longevity, and/or fecundity (