Groundnut Ringspot Orthotospovirus: An Emerging Problem for Soybean Production in São Paulo State

ABSTRACT Orthotospoviruses affect vegetable, leguminous and ornamental plants globally and are transmitted by thrips (Order Thysanoptera). In Brazil, groundnut ringspot orthotospovirus (GRSV) has recently been reported infecting soybean plants in Bahia state and the Federal District. To ascertain the impact of orthotospoviruses on soybean cultivation, soybean leaves and thrips were collected from 2020 to 2022 in the most important soybean‐producing areas of São Paulo State. Virus detection was conducted through reverse transcription‐PCR, followed by partial sequencing of the nucleocapsid gene. Additionally, morphological identification of the thrips was performed. GRSV was found to be widespread across São Paulo State's soybean fields, with Frankliniella schultzei identified as the predominant thrips species over Caliothrips phaseoli and Frankliniella occidentalis . Partial genomes of GRSV isolates revealed a high degree of identity in the nucleocapsid gene sequences. Biological assays involving four distinct GRSV isolates from soybeans demonstrated variable sap transmission efficacy to soybean, tomato, sweet pepper and tobacco plants, some isolates not being transmitted. Seeds obtained from infected soybean plants were grown, and two seedlings out of 1000 tested were positive for GRSV. To the best of our knowledge, this is the first evidence of GRSV seed transmission and because GRSV is the predominant orthotospovirus in Brazil, these findings have great epidemiological implications on orthotospovirus epidemiology.