# Genetic Diversity of Potato Leafroll Virus (Polerovirus PLRV) Is Shaped by Variant Displacements and Selective Pressures Imposed by Aphid and Tuber Transmission Routes

## TL;DR

A new type of Potato Leafroll Virus has become dominant in Scotland, possibly due to transmission methods affecting genetic diversity.

## Contribution

The study identifies a novel PLRV type and links transmission routes to genetic diversity patterns in structural and non-structural genes.

## Key findings

- A novel PLRV variant displaced older variants in Scottish crops by 2023.
- Aphid transmission reduces genetic diversity in PLRV structural genes but not in non-structural genes.
- Tuber transmission allows higher genetic diversity in PLRV structural genes in late field generations.

## Abstract

Potato leafroll virus (PLRV, species Polerovirus PLRV) is a major pathogen affecting potatoes worldwide. Since 2018, PLRV incidence has increased in Scottish potato crops. Deep sequencing of PLRV in Scottish potato plants revealed the prevalence of a novel PLRV type which became predominant in 2023, displacing the phylogenetically distinct variants that have been present in the region since at least 1989. Analysis of the infection dynamics of the cDNA clone-derived PLRV isolates in potato plants indicated that the novel PLRV may accumulate to higher levels compared to the historic one. Analysis of the genetic diversity of PLRV in early and late field generations (FGs) of seed potatoes showed a significantly reduced genetic diversity of the PLRV structural genes in the early FGs compared to the late FGs, while divergency of the non-structural genes remained similar across all FGs. Considering that late FGs are more likely to be infected with PLRV via tuber transmission, and early FGs via aphid transmission, these findings suggest that aphid transmission imposes a genetic bottleneck on the structural genes of PLRV, but not on its non-structural genes.