Turnip Mosaic Virus Infection Differentially Modifies Cabbage Aphid Probing Behavior in Spring and Winter Oilseed Rape (Brassica napus).

Abstract

Simple SummaryWinter oilseed rape accounts for about 90% of total oilseed rape planting area in China, with the majority of it concentrated in the Yangtze River basin. The remaining 10% is mostly found in the provinces of China’s northwest plateau. Winter oilseed rape areas in China have gradually expanded to the north in the last decade, resulting in cabbage aphids and turnip mosaic virus (TuMV). The aphid is a vector for TuMV and is gradually increasing on winter and spring oilseed rape. Quantifying the probing behaviors of the aphids on spring oilseed rape and winter oilseed rape helps us to understand TuMV regulation of the aphids. We found that compared to mock-inoculated plants, cabbage aphids on infected plants increased brief probing frequency, cell penetration frequency, intracellular probing time, decreased time to first probe and pathway duration, potentially promoting viral acquisition and minimizing viral loss and plant damage. Viruliferous aphids had reduced pathway duration, increased cell penetration frequency, increased intracellular probing time, increased salivation frequency, and ingested less sap compared with non-viruliferous aphids, primed for viral infection. TuMV infection also differentially modified aphid feeding behavior on winter and spring oilseed rape cultivars, primarily on uninfected plants.Direct and indirect effects of plant virus infection on vector behavior have been discovered to improve virus transmission efficiency, but the impact of plant cultivars in virus–vector–plant interactions has received little attention. Electropenetrography (EPG) allows real-time tracking and quantification of stylet penetration behaviors, pathogen transmission, and plant resistance mechanisms. Quantitative probing behaviors on a spring oilseed rape cultivar, ‘Xinyou17’, and a winter oilseed rape cultivar, ‘Zheping4’, were investigated using EPG to compare turnip mosaic virus (TuMV) regulation of cabbage aphid probing behavior. Results for indirect effects showed that compared to mock-inoculated plants, cabbage aphids on infected plants increased brief probing frequency, cell penetration frequency, intracellular probing time, and decreased time to first probe and pathway time, potentially promoting viral acquisition. TuMV also directly influences aphid probing behavior. Viruliferous aphids had reduced pathway time, increased cell penetration frequency, increased intracellular probing time, increased salivation frequency, and ingested less sap than non-viruliferous aphids, primed for viral infection. Although oilseed rape cultivars can also influence aphid behavior, the main effect of cultivars was not significant on TuMV-infected plants.