Soilborne wheat mosaic disease (SBWMD), originally attributed to infections by Soilborne wheat mosaic virus (SBWMV) and Wheat spindle streak mosaic virus (WSSMV), is one of the most frequent virus diseases and causes economic losses in wheat in southern Brazil. This study aimed to characterize molecularly the viral species associated with wheat plants showing mosaic symptoms in Brazil. Wheat leaves and stems displaying mosaic symptoms were collected from different wheat cultivars in Passo Fundo municipality, Rio Grande do Sul State, southern Brazil. Double‐stranded RNA was extracted and submitted to cDNA library synthesis and next‐generation sequencing. No sequences of SBWMV and WSSMV were detected but the complete genome sequence of a putative new member of the family Benyviridae was determined, for which the name wheat stripe mosaic virus (WhSMV) is proposed. WhSMV has a bipartite genome with RNA 1 and RNA 2 organization similar to that of viruses belonging to Benyviridae. WhSMV RNA 1 has a single open reading frame (ORF) encoding a polyprotein with putative viral replicase function. WhSMV RNA 2 has six ORFs encoding the coat protein, the major protein (read‐through), triple gene block movement proteins (TGB 1, 2 and 3) and ORF 6 (hypothetical protein). In addition to the genomic organization and nucleotide and amino acid sequence identities, phylogenetic analyses also corroborated that WhSMV is a virus species of the Benyviridae. However, isolates of WhSMV formed a clade distinct from members of the genus Benyvirus. It was also demonstrated that the plasmodiophorid Polymyxa graminis is associated with wheat roots showing SBWMD symptoms and infected by WhSMV.

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Soil-borne wheat mosaic disease (SBWMD) caused by wheat stripe mosaic virus (WhSMV) is one of the most important viral diseases of wheat in Brazil. Farmers have used crop rotation (CR) successfully to reduce the incidence of many diseases in wheat. CR can contribute along with genetic resistance in the management of SBWMD. The objective of this study was to evaluate the effect of CR in SBWMD incidence and wheat yield as compared with wheat monoculture (W). During 2017 and 2018 growth seasons, in a long-term experiment, W and three CR: W1white oats-wheat; W2vetch-white oats-wheat; and W3black oatsbarley-black oats-wheat were evaluated using three wheat cultivars: BRS Parrudo (resistant), BRS Reponte (moderately resistant) and BRS Guamirim (susceptible). The rainiest season (2018) was more favorable to the development of the disease. In this year, CR W2 and W3 significantly decreased SBWMD incidence by 90% compared to wheat monoculture. Also, grain yield (GY) differences between CR were higher in the rainiest season. GY increases up to 58% (BRS Reponte), 81% (BRS Guamirim) and 106% (BRS Parrudo) in W2 and W3. The use of plant species that are non-hosts of WhSMV may be one of the main factors that contribute to the reduction of SBWMD levels.

O tratamento de sementes (TS) é uma importante ferramenta no manejo de doenças na cultura do trigo, embora poucos produtos sejam indicados para esse fim. Por isso, a pesquisa deve realizar trabalhos relacionados à efetividade de diferentes produtos no TS e também o possível efeito fitotóxico. Os objetivos deste trabalho foram realizar testes fisiológicos em sementes e avaliar o desenvolvimento de duas cultivares de trigo (BRS Guamirim e TBIO Toruk), submetidas a 13 diferentes tratamentos de sementes. Para cada tratamento foram analisados a germinação e o vigor. As sementes tratadas também foram semeadas a campo, onde se determinou a emergência a campo e massa fresca de raiz e parte aérea. As sementes tratadas com azoxistrobina e Bacillus amyloliquefaciens resultaram em decréscimo na germinação da cultivar TBIO Toruk. Na análise do vigor houve diferença entre os tratamentos testados para as duas cultivares, sendo que houve redução do vigor em sementes tratadas com dimetomorfe para TBIO Toruk e azoxistrobina para a cultivar BRS Guamirim. As sementes submetidas ao tratamento Carboxamida A resultaram em plântulas com maiores valores de massa fresca de raiz e parte aérea. Os resultados apresentados permitem a seleção de produtos com baixa ou ausência de fitotoxidade para incorporação no manejo de doenças no trigo.

Wheat was introduced in Brazil with the arrival of European settlers. For a long time, it was cultivated on a smaller scale until, in the 1960s-1970s, changes in the eco¬nomic-technological situation resulted in a significant increase in the cultivated area. During this period, there was also an increase in the importance of several phytosan¬itary problems. The 1960s-1970s mark the first scientific records describing viruses as pathogens of this culture in the country. The history of knowledge about viruses in wheat in Brazil has as important elements: (i) changes in the production systems and in the agricultural landscape; (ii) new technologies and tools for the study of viruses; and (iii) introductions of viruses and their vectors in the national territory.