Articles
Biology and management of Sw-5 resistance-breaking Tomato spotted wilt virus isolates in Central California
Article number
1351_15
Pages
95 – 102
Language
English
Abstract
Genetic resistance to Tomato spotted wilt virus (TSWV) is present in most processing tomato cultivars grown in California.
However, in 2016, a resistance-breaking (RB) isolate of TSWV was detected in three tomato production areas in Central California.
To evaluate overwintering potential, weeds and crops were collected and tested for RB where the isolate had been confirmed in tomatoes the previous season in early in 2017 and 2018. Of the winter weeds and crops sampled in February and March, RB TSWV was detected in Sonchus oleraceus and in commercial lettuce.
For comparison of relative susceptibility of processing tomato cultivars, entries in commercial cultivar trials through Central California were evaluated for disease incidence and severity.
From 2019 to 2021, 18 trials were evaluated and rating from 27 entries were analyzed.
The average percentages of TSWV-symptomatic plants differed among entries with BP13, SV8011TM, SVTM1082, UG29814, H1662 and BQ413 having significantly lower symptom incidence than the most highly impacted cultivars.
From two to three commercial cultivar trials per year, each of four to eight representative cultivars were sampled and tested.
In the trials evaluated, RB was detected in all Sw-5 cultivars as well as in the susceptible cultivars tested.
Insecticide efficacy against the thrips vector of TSWV was compared in a 13 treatment, four replication trial in 2021. However, only a Verimark transplant treatment significantly reduced thrips densities, only for 15 days.
Presence of RB in winter crops and weeds, and in non-Sw-5 tomatoes suggests that the isolate will persist in Central California.
Since genetic resistance will not protect tomatoes from TSWV and insecticides are inconsistent and deliver marginal levels of control of the thrips vector, current management depends upon multiple strategies including selection of less susceptible cultivars in high risk areas, avoidance of known virus sources, destruction of hosts and weeds.
However, in 2016, a resistance-breaking (RB) isolate of TSWV was detected in three tomato production areas in Central California.
To evaluate overwintering potential, weeds and crops were collected and tested for RB where the isolate had been confirmed in tomatoes the previous season in early in 2017 and 2018. Of the winter weeds and crops sampled in February and March, RB TSWV was detected in Sonchus oleraceus and in commercial lettuce.
For comparison of relative susceptibility of processing tomato cultivars, entries in commercial cultivar trials through Central California were evaluated for disease incidence and severity.
From 2019 to 2021, 18 trials were evaluated and rating from 27 entries were analyzed.
The average percentages of TSWV-symptomatic plants differed among entries with BP13, SV8011TM, SVTM1082, UG29814, H1662 and BQ413 having significantly lower symptom incidence than the most highly impacted cultivars.
From two to three commercial cultivar trials per year, each of four to eight representative cultivars were sampled and tested.
In the trials evaluated, RB was detected in all Sw-5 cultivars as well as in the susceptible cultivars tested.
Insecticide efficacy against the thrips vector of TSWV was compared in a 13 treatment, four replication trial in 2021. However, only a Verimark transplant treatment significantly reduced thrips densities, only for 15 days.
Presence of RB in winter crops and weeds, and in non-Sw-5 tomatoes suggests that the isolate will persist in Central California.
Since genetic resistance will not protect tomatoes from TSWV and insecticides are inconsistent and deliver marginal levels of control of the thrips vector, current management depends upon multiple strategies including selection of less susceptible cultivars in high risk areas, avoidance of known virus sources, destruction of hosts and weeds.
Publication
Authors
T.A. Turini, C.S. Stoddard, R.L. Gilbertson
Keywords
Tomato spotted wilt virus, Sw5, resistance-breaking, varietal tolerance, host range
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