Tomato spotted wilt virus resistance breaking strains in Australia

Abstract

Resistance to tomato spotted wilt virus (TSWV) in commercial tomatoes and capsicums are controlled by two single dominant genes, Sw5b and Tsw. The Sw5b was identified in Solanum peruvianum and has been introgressed into tomato lines for high level resistance against TSWV and other tospoviruses. TSWV resistant capsicum lines have the Tsw gene originally from Capsicum chinense ‘PI’ accessions. Resistance is displayed as a hypersensitive response, which prevents systemic spread of the virus. There has been the emergence of resistance-breaking strains of TSWV, both worldwide and occasionally in Australia. The Sw5b resistance-breaking strains exhibiting a conserved mutation in the NsM gene, the viral movement protein. Resistance-breaking of the Tsw gene has been identified as changes in the NsS gene (silencing suppressor), but no consensus has been reached on what changes contribute to the phenotype. We have sequenced TSWV isolates from across Australia from a variety of crops and alternative hosts, collected over the last 40 years with a number of these isolates wellcharacterised for Tsw resistance-breaking. We will present the current situation of resistance-breaking isolates in Australia.