Healthy R. padi aphids were allowed a 24 h AAP on membranes, as described previously, which contained 40 mg/ml of purified virus in 15% sucrose buffered with 0.01 M phosphate buffer, pH 7. The following virus treatments used were preparations containing 1) phosphate buffer only, 2) phosphate buffer including EDTA only, and 3) phosphate buffer including Na 2 SO 3 only. To examine an aphid's ability to acquire virus, after 24 h, six aphids were collected, divided randomly into three groups of two for each treatment and stored at 280uC in 25 ml nuclease-free water in an RNase-free microcentrifuge tube. The remaining aphids were transferred to healthy oat seedlings (Coast black), placing five aphids per seedling. Aphids were allowed a 3 day IAP to test for transmissibility of the virus, and aphids were collected to examine the treatment effects on virus uptake into the hemocoel. For each virus treatment, six aphids were collected, divided randomly into three groups of two for each treatment and stored at 280uC in 25 ml nuclease-free water in an RNase-free microcentrifuge tube. Total RNA was isolated, five ml of RNA was used in an RT-PCR as described [14] , with the exception that primers specific for the coat protein of CYDV-RPV (RPV-CP For: 59-ATGAGTACGGTCGTCCTTAGATCC-39; RPV-CP Rev: 59-CTATTTTGGGTTTTGTAGCTGGAC-39) were used to amplify a 614 bp fragment.