S. elaeagnifolium

Invasive weeds S. elaeagnifolium and S. rostratum shown as ToBRFV hosts in new paper

In a new paper published in the PLOS ONE journal, VIRTIGATION partner Volcani Center identifies the invasive weeds Solanum elaeagnifolium and Solanum rostratum as potential ToBRFV hosts.

Invasive weeds as significant threat to horticulture

Invasive weeds such as S. elaeagnifolium (i.e. Silverleaf nightshade) and S. rostratum (i.e. Buffalo bur) are a significant threat to horticultural crops like tomatoes and cucurbits, causing major yield losses worldwide. Due to various factors driven by humankind, including import-export trade and climate change, invasive weeds are on the rise. The greatest indirect impact of these weeds on crop yield stems from their role as virus reservoirs within commercial growing areas. At the same time, emerging plant viruses like ToBRFV are wreaking havoc on tomato crops. Partial host plant analyses for ToBRFV previously identified various weed species of genus Solanum, such as Solanum nigrum (i.e. Black nightshade), as potential ToBRFV hosts. Identifying ToBRFV potential weed hosts is therefore crucial in ensuring efficient disease management practice for weed control throughout the tomato production cycle, according to the Volcani Center authors.

Role of S. elaeagnifolium & S. rostratum as ToBRFV hosts

In their experimental study, the Volcani Center researchers sought to determine the potential of invasive weeds as hosts of ToBRFV. For this, they tested various invasive weeds common within commercial tomato growing areas (e.g., in greenhouses and open fields), including S. elaeagnifolium and S. rostratum. In their experimental design, the Israeli scientists collected and tested two endemic weeds and nine major invasive weeds of the Israeli flora. Through a series of viral inoculations and bioassays, serological tests for viral infections (i.e. ELISA and western blot analyses), viral RNA extraction and reverse transcription (RT)-PCR, as well as quantitative RT-PCR, they were able to identify the invasive Solanaceae species S. elaeagnifolium and S. rostratum as hosts of ToBRFV. 

S. elaeagnifolium ToBRFV
Figure depicting S. elaeagnifolium as a host of ToBRFV, with a low virus titer © 2023 Dombrovsky et al., PLOS ONE journal

The Volcani Center authors observed no phenotype on ToBRFV-infected S. elaeagnifolium grown in the wild or following ToBRFV sap inoculation. S. rostratum plants inoculated with ToBRFV contained a high ToBRFV titer compared to ToBRFV-infected S. elaeagnifolium plants. They also tested the infectious potential of ToBRFV-inoculated S. elaeagnifolium plants by inoculating tomato plants, which became infected by ToBRFV. Although being low in ToBRFV titer, infected S. elaeagnifolium plants still could serve as a primary infection source.

S. rostratum ToBRFV
Figure depicting S. rostratum as a host of ToBRFV © 2023 Dombrovsky et al, PLOS ONE journal

Distribution & abundance of these Solanaceae species increase risks of virus transmission between species

In Israel, the S. elaeagnifolium infests agricultural and non-agricultural habitats including field crops, roadsides and waste grounds. The potential of S. elaeagnifolium as a host of crop plant pests is already known, as it is e.g. a natural host of TYLCV. The findings of Volcani Center’s authors that S. elaeagnifolium is now also a host for ToBRFV should concern the actors of the tomato value chain in particular. The same counts for the identification of S. rostratum as ToBRFV host. S. rostratum is found mainly within field and at field crop margins, not only of tomatoes, but also of cucurbits like watermelons. The Volcani Center authors conclude that the distribution and abundance of these weed species within and in close proximity to tomato fields, but also other horticultural fields increase the risks of virus transmission between species. However, they also highlight the unique response of S. elaeagnifolium to inoculations with ToBRFV, that could indicate that the unique plant defense response determines the low virus titer as well as phenotype preservation. The Israeli scientists deem this worth further research as a tool for the development of virus-resistant varieties.

More info about Volcani Center's research

The full version of Volcani Center’s paper in the PLOS journal titled “Solanum elaeagnifolium and Srostratum as potential hosts of the tomato brown rugose fruit virus” is available online here since 1 March 2023. It has been authored by one of Volcani Center principal investigators in VIRTIGATION, Aviv Dombrovsky, as well as scientist Elisheva Smith. The dataset underlying Volcani Center’s peer-reviewed, open access scientific publication is available in the VIRTIGATION Zenodo community. Find out more about VIRTIGATION’s scientific publications on our website here.