Within-Plant Accumulation of Potato Leafroll Virus by Aggregated Green Peach Aphid Feeding

Abstract

Aggregates of 20 green peach aphids placed on noninoculated leaves of plants previously inoculated with potato leafroll virus (PLRV) caused significantly more accumulation of PLRV at their feeding sites than in aphid-free leaves in both potato and Physalis floridana. Based on comparable periods of postinoculation, six times more viral antigen was detected by enzyme-linked immunosorbent assay in inoculated leaves of P floridana than of potato. The amount of PLRV detected in inoculated leaves was significantly correlated with the amount of PLRV that accumulated in aggregate feeding leaves, indicating that systemic spread of PLRV was titer-dependent. The movement of PLRV to aggregated aphid feeding sites probably followed the path of metabolites directed to the site of aphid damage and/or nutrient withdrawal. The accumulation of PLRV was not specific to the area of aggregated feeding but was evident throughout the leaf supporting the aphid colony. Aphids feeding in aggregates provided a mechanism that optimized virus acquisition from infected plants in which the pathogen was not uniformly distributed.