Genetic variability of two Mexican Tomato brown rugose fruit virus isolates and expression of symptoms in tomato and pepper

Abstract

Objective/Background. The objective was to analyze the variability of two Mexican isolates of ToBRFV after a process of inoculation and multiplication in different commercial and Mexican landraces of tomato (Solanum lycopersicum) (15 materials) and pepper (Capsicum annuum) (20 materials), and to evaluate the expression of symptoms under greenhouse conditions. Materials and Methods. In greenhouses, the post-infection variability of two isolates was analyzed: EM-JI2021 (State of Mexico) and C-JI2021 (Colima) in 15 genotypes of tomato and 20 of pepper. Each isolate was mechanically inoculated on five plants per genotype with a total of 150 plants (56 days old) of tomato and 200 of pepper. Three plants per genotype were used as controls. Sixty-one days after inoculation, one leaf per plant was collected for RT-PCR. Incidence and symptom expression were recorded. RNA extraction was by 2% CTAB. ToBRFV-F/ ToBRFV-R primers amplifying 475 bpb of the RpRd gene were used (SENASICA-CNRF). 24 RT-PCR products were sequenced, cleaned and aligned with NCBI Genbank records using MEGAv11.0.13. Based on epidemiological criteria, 34 sequences were selected from GenBank for variability analysis. Results. Ten days after inoculation, tomato genotypes exhibited severe mosaic, mild mosaic, and reduced leaf area. In pepper, symptoms differentiated by genotype were observed, including hypersensitivity reaction, leaf deformation, stem necrosis, mosaic, yellowing, necrotic lesions, and asymptomatic condition. Between position 2,124 to 2,500 bp there was 99.74 % homology with the first report of ToBRFV in Jordan (KT383474.1). Homology >99.74 % was found with isolates from USA (MT002973.1) and Canada (OQ674195.1). C-JI2021 exhibited no variability, while EM-JI2021 generated three haplotypes: One nucleotide change (c.2,355T>C) was detected in Mulato (pepper) and Don R (tomato), while two substitutions (c.2,278A>T; c.2,355T>C) were detected in Santawest, Altius, Sahariana and Nebula (tomato). Conclusion. The pathogenic intensity of ToBRFV varied from asymptomatic to severe depending on the combination of host, genotype, and haplotype. In short periods of infection, three haplotypes were detected, suggesting host-dependent mutagenic capacity of the virus.