Seed Transmission of Tobamoviruses: Aspects of Global Disease Distribution

Abstract

Global seed trade contributed to development and improvement of world agriculture. An adverse effect of global seed trade is reflected in disease outbreaks in new growing areas, countries, and continents. Among the seed-borne viruses, Tobamovirus species are currently considered a peril for crop production around the world. The unique tobamoviral particles confer stability to the RNA genome and preserve their infectivity for years. High titer of Tobamovirus species accumulates in reproductive organs leading to viral particles adsorbed to seed coat, which potentially establish a primary infectious source. Tobamovirus-contaminated seeds show very low virus transmission in grow-out experiments as detected by enzyme-linked immunosorbent assay (ELISA) and reverse transcription polymerase chain reaction (RT-PCR) analysis. Interestingly, in situ immunofluorescence analysis of Cucumber green mottle mosaic virus (CGMMV) reveals that the perisperm-endosperm envelope (PEE) is contaminated as well by the Tobamovirus. Indeed, chemical seed disinfection treatments that affect primarily the seed coat surface are efficient for several Tobamovirus species but apparently do not prevent seed transmission of CGMMV to occur. Tobamovirus infection of the seed internal layers, which rarely includes the embryo, may partially follow the direct invasion pathway of Potyviruses such as Pea seed-borne mosaic virus (PSbMV) to pea embryo.

Paths of cucumber green mottle mosaic virus disease spread and disinfectant‐based management

“…Unlike potyviruses, members of the Tobamovirus genus in general and CGMMV in particular are highly stable and efficiently transmitted mechanically through contact with planting equipment and worker hands (Harper, Hull, Lockhart, & Olszewski, 2002; Rao & Varma, 1984; Reingold et al, 2016). Since its worldwide spread (Dombrovsky et al, 2017; Dombrovsky & Smith, 2017), CGMMV posed a challenge to the discovery of effective disinfectants that would eventually control its high distribution. CGMMV is a seed borne virus and up to date seed disinfection treatments were insufficient for complete inactivation (Reingold, Lachman, Blaosov, & Dombrovsky, 2015).…”

Tomato brown rugose fruit disease: current distribution, knowledge and future prospects

“…Greenhouses versus open field cultivation Tobamoviruses are mechanically transmitted, seedborne viruses that show very low seed transmission rates (Taylor et al, 1961;Genda et al, 2011;Sastry, 2013;Dombrovsky & Smith, 2017). Nonetheless, it is evident from all available reports that this new disease is capable of being mechanically transmitted through infected sap via any means, e.g.…”

“…Plant viruses belonging to the genus Tobamovirus , currently comprising 37 species, have rod‐shaped particles, encapsulating a positive‐sense, single‐stranded RNA (+ssRNA) genome of approximately 6.4 kb (Dombrovsky & Smith, ). The genome organization of ToBRFV has been described as typical of the genus Tobamovirus , the largest in the family of Virgaviridae, and therefore related to TMV, ToMV, tomato mottle mosaic virus (ToMMV), cucumber green mottle mosaic virus (CGMMV) and odontoglossum ringspot virus (ORSV) (Adams et al , , ).…”

“…Similarly, under certain conditions, pepper plants harbouring the L resistance genes L 1 , L 2 and L 3 have also been jeopardized (Luria et al , ). The stable and virulent nature of this virus means there is a high potential to cause damage to tomato and pepper as major hosts, particularly under protected environments such as greenhouses and net houses, where there are mostly monoculture crops, frequently without crop rotations or breaks between growing cycles, making them highly susceptible to tobamovirus infection and spread (Dombrovsky & Smith, ). The productivity and quality of infected tomato and pepper fruits can thus be affected, thereby downgrading the market value of the fruit, increasing the production costs in an attempt to mitigate the disease, and indirectly changing the cultural practices of most growers.…”

Plant Viruses Infecting Solanaceae Family Members in the Cultivated and Wild Environments: A Review

“…A similar transmission route has also been hypothesized (but so far not confirmed) for pepino mosaic virus (PepMV) and Olpidium virulentus in tomato plants [20], and the existence of an additional transmission pathway for potato virus Y (PVY) involving mycorrhizal networks created by hyphae of arbuscular mycorrhizal fungi has been hypothesized [21], again without confirmation so far. On the other hand, vertical transmissions through seeds or pollen are also documented, e.g., tobamoviruses [22], PepMV [23] or tomato torrado virus (ToTV) [24] infecting various Solanaceae species.…”