Cross‐protection or enhanced symptom display in greenhouse tomato co‐infected with different <i>Pepino mosaic virus</i> isolates

Abstract

The potential of three mild Pepino mosaic virus (PepMV) isolates, belonging to the CH2, EU and LP genotypes, to protect a tomato ( Solanum lycopersicum ) crop against an aggressive challenge isolate of the CH2 genotype was assessed in greenhouse trials and PepMV symptoms were rated at regular time points. After challenge infection, enhanced symptom display was recorded in plants that were pre‐inoculated with a protector isolate belonging to a different genotype (EU, LP) from the challenge isolate. A quantitative genotype‐specific TaqMan assay revealed that in these plants, the accumulation of the challenge isolate only temporarily slowed down. By contrast, efficient cross‐protection was obtained using the mild isolate of the CH2 genotype, and in this case the challenge isolate was barely detectable in the pre‐inoculated plants. These results suggest that the interaction between PepMV isolates largely depends on RNA sequence homology and that post‐transcriptional gene silencing plays an important role in cross‐protection.