Impact of Host Resistance to Tomato Spotted Wilt Orthotospovirus in Peanut Cultivars on Virus Population Genetics and Thrips Fitness

Pin-Chu Lai,Sudeep Bag,Albert K Culbreath,Rajagopalbabu Srinivasan,Mark R Abney

doi:10.3390/pathogens10111418

Abstract

Thrips-transmitted tomato spotted wilt orthotospovirus (TSWV) is a major constraint to peanut production in the southeastern United States. Peanut cultivars with resistance to TSWV have been widely used for over twenty years. Intensive usage of resistant cultivars has raised concerns about possible selection pressure against TSWV and a likelihood of resistance breakdown. Population genetics of TSWV isolates collected from cultivars with varying levels of TSWV resistance was investigated using five TSWV genes. Phylogenetic trees of genes did not indicate host resistance-based clustering of TSWV isolates. Genetic variation in TSWV isolates and neutrality tests suggested recent population expansion. Mutation and purifying selection seem to be the major forces driving TSWV evolution. Positive selection was found in N and RdRp genes but was not influenced by TSWV resistance. Population differentiation occurred between isolates collected from 1998 and 2010 and from 2016 to 2019 but not between isolates from susceptible and resistant cultivars. Evaluated TSWV-resistant cultivars differed, albeit not substantially, in their susceptibility to thrips. Thrips oviposition was reduced, and development was delayed in some cultivars. Overall, no evidence was found to support exertion of selection pressure on TSWV by host resistance in peanut cultivars, and some cultivars differentially affected thrips fitness than others.

Highlights

Resistant cultivars often form the first line of defense against arthropod-borne plant viruses such as the thrips-transmitted tomato spotted wilt orthotospovirus (TSWV)
Intensive screening and breeding efforts over the three decades led to consistent releases of peanut cultivars with incremental levels of TSWV resistance [6]
Phylogenetic trees were constructed based on nucleotide polymorphisms observed in Phylogenetic trees were constructed based on nucleotide polymorphisms observed full length of the N gene, and partial sequences of NSs, NSm, Gn/Gc, and RNA-dependent RNA polymerase (RdRp) genes using in full length of the N gene, and partial sequences of NSs, NSm, Gn/Gc, and RdRp genes

Summary

Introduction

Published: 1 November 2021Resistant cultivars often form the first line of defense against arthropod-borne plant viruses such as the thrips-transmitted tomato spotted wilt orthotospovirus (TSWV). TSWV infection leads to spotted wilt disease in peanut, which has been a severe limiting factor in peanut (Arachis hypogaea L.) production in the southeastern United. TSWV infection in peanut was first reported in Texas in 1971 and has since spread to other southern states [2,7]. In the 1990s, TSWV became a yield-limiting problem in peanut in the southeastern. Observations indicated variation in susceptibility to TSWV among peanut cultivars. Intensive screening and breeding efforts over the three decades led to consistent releases of peanut cultivars with incremental levels of TSWV resistance [6]. Resistance to TSWV in peanut is commonly referred to as field resistance or tolerance and is typified by milder symptoms following TSWV infection and increased yield compared with TSWV-susceptible cultivars, especially under high virus

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Conclusion