Natural Infection of Cichorium intybus (Asteraceae) by Groundnut Ringspot Virus (Genus Orthotospovirus) Isolates in Brazil

Abstract

Leaf chicory (Cichorium intybus L.) is a nutritionally rich vegetable used in regional cuisine in Brazil. Plants of C. intybus displaying symptoms (viz. chlorotic and necrotic ringspots, mosaic, and leaf deformation) similar to that induced by orthotospoviruses (genus Orthotospovirus, family Tospoviridae) were observed in three fields (≈ 0.2 ha each) in Gama County, in the Federal District, Brazil, from September 2016 to January 2020 in plants of the cultivars ‘Folha-Larga’ and ‘Spadona’ (Fig. 1). Incidence of symptomatic plants was nearly 10% in each field. Transmission electron microscopic examination of thin sections from symptomatic leaf samples showed typical membrane-bounded orthotospovirus particles within cisternae of spongy parenchymal cells (Fig 2). Two individual leaf samples per field were collected and submitted to dot enzyme-linked immunosorbent assay with polyclonal antisera against N protein of tomato spotted wilt virus (TSWV), groundnut ringspot virus (GRSV) and tomato chlorotic spot virus (TCSV). Symptomatic samples strongly reacted only against GRSV antibodies. Total RNA was extracted (Trizol®, Sigma) from all six samples and used as template in RT-PCR assays. The primer J13 (5’-CCCGGATCCAGAGCAAT-3’) was employed for cDNA synthesis using M-MLV reverse transcriptase. PCR assays were done with the primer pair BR60/BR65 (Eiras et al., 2001) to obtain ≈ 500 bp fragment of untranslated region and partial N gene in the S RNA segment from each sample. Purified RT-PCR products of two randomly selected individual samples were directly sequenced (GenBank MW467981 and MZ126602) and their BLASTn analyses displayed 99 to 100% nucleotide identity to GRSV isolates previously reported infecting C. endivia L. in Brazil (Jorge et al., 2021). Our analyses combining N protein serology and N-gene sequencing (both directed to the S RNA segment) allowed us to confirm the GRSV infection of C. intybus, but the potential reassortant nature of these isolates (Webster et al., 2015; Silva et al., 2019) are unknown since their M RNA segments were not characterized. Individual leaf extracts (in phosphate buffer, pH 7.0) of the sequenced isolates were mechanically inoculated onto ten seedlings of two C. intybus cultivars (‘Folha Larga’ and ‘Pão-de-Açúcar’) and three plants each of the indicator hosts Capsicum chinense PI 159236, Nicandra physalodes; Nicotiana rustica; Datura stramonium; and tomato cv. Santa Clara. Systemic chlorotic and necrotic ringspots, mosaic, and leaf deformation developed in the indicator hosts and infection by GRSV was confirmed via serological assays 20 days after inoculation. However, no symptoms and no serological reaction to GRSV antibodies were observed on the C. intybus cultivars even after two successive mechanical inoculations. This transmission failure might be due to factors such as the requirement of the thrips vector(s), physicochemical barriers in the foliage or the presence of non-mechanically transmissible helper agent(s) necessary to ensure GRSV infection of C. intybus. The natural infection of C. intybus by a not fully characterized orthotospovirus (mostly likely TSWV) has been observed since 1938 in Brazil (Kitajima, 2020). Our report of GRSV infecting C. intybus is thus confirming previous speculations that similar symptoms in this vegetable crop were induced by orthotospovirus infection in Brazil. References: Eiras, M. et al. 2001. Fitopatol. Bras. 26: 170. Jorge, T. S. et al. 2021. Plant Dis. 105: 714. Kitajima, E.W. 2020. Biota Neotrop. 20: e2019932. Silva, J. M. F. et al. 2019. Viruses 11: 187. Webster, C.G. et al. 2015. Phytopathology 105: 388.

Effects of physalis rugose mosaic and groundnut ringspot viruses, in single and double infections, on the development, yield and postharvest fruit characteristics of Physalis peruviana plants

“…peruviana , Pisum sativum and Zinnia spp. (De Oliveira et al, 2022; Jorge et al, 2022; Kitajima, 2020). It is transmitted by thrip species of the genus Frankliniella in a persistent propagative manner.…”

Novel sources of resistance/tolerance to orthotospoviruses in Lactuca germplasm identified via field exposure to viruliferous vectors and in greenhouse mechanical transmission assays

“…GRSV was initially reported in Africa infecting legume crops, being subsequently detected affecting a wide range of host plants in different countries in South America, North America, and Asia ( However, more extensive regional surveys indicate that TSWV and GRSV are the main orthotospoviruses associated with lettuce and other crops in Brazil (Boiteux et al 1995;Fonseca et al 1995;Lima et al 2016;Martinez et al 2019) and Argentina (Gracia et al 1999). The symptoms induced by either TSWV or GRSV in lettuce are indistinguishable, providing no clear indication of which species would be involved, requiring serological analyzes and/or molecular methods for a suitable identi cation of the associated pathogens (Jorge et al 2023a).…”

“…Due to the lack of curative methods as well as e cient chemical control of the vectors, the management of diseases induced by orthotospoviruses is di cult. In this situation, genetic resistance is the most practical and sustainable strategy (Jorge et al 2023a). Sources of orthotospovirus resistance have been reported in tomato and Capsicum (Jorge et.…”

“…In this situation, genetic resistance is the most practical and sustainable strategy (Jorge et al 2023a). Sources of orthotospovirus resistance have been reported in tomato and Capsicum (Jorge et. al.…”

“…Seven Orthotospovirus species have been reported under Brazilian conditions (Costa & Forster 1941;Duarte et al 1995;Nagata et al 1998;Pozzer et al 1999;Martinez et al 2019;Kitajima 2020). Orthotospovirus tomatomaculae (tomato spotted wilt orthotospovirus -TSWV), Orthotospovirus tomato avi (tomato chlorotic spot orthotospovirus -TCSV), and Orthotospovirus arachianuli (groundnut ringspot orthotospovirus -GRSV) are the prevalent species in vegetable crops and weeds (Jorge et al 2023a).…”