Samara Campos Do Nascimento

Barley yellow dwarf virus (BYDV; Luteovirus pavhordei ) is one of the most economically important viral pathogens of wheat, causing substantial losses in plant growth, physiology, and grain yield. This study evaluated the combined effects of wheat genotype, BYDV infection, and their interaction on agronomic performance and photosynthetic physiology using an integrative multivariate approach. The experiment employed a completely randomized design with four genotypes and two conditions (with and without virus), using controlled inoculation via aphids and infection confirmation by RT-PCR. Growth and yield components, as well as chlorophyll fluorescence variables, were measured, enabling co-analysis using multivariate analysis of variance, canonical discriminant analysis, and principal component analysis to explore patterns of association. The results revealed marked effects of genotype and viral infection on the set of variables, as well as differential responses among genotypes. BYDV infection altered the photosynthetic apparatus, with enhanced energy dissipation mechanisms and reduced photosynthetic efficiency, lowering agronomic performance. Multivariate analyses enabled the identification of association patterns among variables and the discrimination of genotypes based on their tolerance levels to the BYDV. Tolerant genotypes maintained photosynthetic efficiency, accompanied by vegetative growth and yield stability. In contrast, intolerant genotypes exhibited stronger photoprotective responses, greater impairment of PSII photochemistry, and more pronounced reductions in agronomic performance. Overall, this study demonstrates that viral infection reorganizes the relationships among physiological and productive processes, highlighting the importance of integrative approaches for better understanding plant–virus interactions and further supporting breeding programs.

Rice stripe necrosis virus (RSNV) is the causal agent of the disease ‘rice crinkling’ and is transmitted by the protozoan Polymyxa graminis . Although genetic resistance has been explored, no resistant commercial cultivars are currently available. Oryza glaberrima has been identified as a promising source of resistance. However, it remains unclear whether this resistance is effective against the virus, the vector, or both, as well as whether it can be transferred to Oryza sativa cultivars. Disease‐resistant genotypes are primarily selected through visual observations of symptom expression. The absence of a severity scale for RSNV makes this process difficult, and relying solely on visual assessments can introduce subjectivity. We developed a severity scale and a reverse transcripiton‐quantitative PCR (RT‐qPCR) assay for screening resistance levels in rice genotypes against RSNV and its vector and to analyse the genetic variability of RSNV isolates. To achieve absolute quantification, experiments were conducted using O. glaberrima and three O. sativa cultivars. Inoculation occurred naturally using soil from an area with a history of the disease. Visual symptoms were recorded and disease intensity was evaluated. Subsequently, total nucleic acid extraction was performed on the samples and viral and vector loads were quantified through RT‐qPCR and qPCR, respectively. To characterize the virus variability, symptomatic rice samples were collected in the 2021/2022 crop season. RT‐PCR was conducted to amplify the coat protein gene of RSNV, and molecular variability descriptors were analysed.

Twenty-one viruses belonging to 14 genera have been reported to infect P. peruviana worldwide (^{AGUIRRE-RÁQUIRA et al., 2014}; ^{DALLOS et al., 2010}; ^{FARIÑA et al., 2019}; ^{GÁMEZ-JIMÉNEZ et al., 2009}; ^{GARCÍA et al, 2020}; ^{GRAÇA et al. 1985}; ^{GUTIÉRREZ et al., 2015}; ^{KISTEN et al., 2016}; ^{PRAKASH et al., 1988}; ^{SALAMON; PALKOVICS, 2005}; ^{THOMAS; HASSAN, 2002}; ^{TRENADO et al., 2007}). In Brazil, there have been reports of two orthotospoviruses, tomato chlorotic spot virus (TCSV) and groundnut ringspot virus (GRSV) (^{EIRAS et al., 2012}; ^{ESQUIVEL et al., 2018}), and a putative new sobemovirus named physalis rugose mosaic virus (PhyRMV) (FARIÑA et al., 2019).

The soil-borne wheat mosaic disease (SBWMD) significantly impacts wheat crops. In Brazil, this disease is caused by the wheat stripe mosaic virus (WhSMV). Typical symptoms of SBWMD were observed in a commercial wheat field in Campos Novos, Santa Catarina, Brazil. This study aimed to elucidate the etiological agent of SBWMD in wheat crop in the state of Santa Catarina. Total RNA was extracted from symptomatic sample using TRIzol, following subsequent RT-PCR. Specific primer pairs were used to amplify genomic regions of 641 bp and 872 bp, corresponding to the coat protein (CP) and partial replicase genes, respectively. Amplicons were sequenced and the resulting nucleotide sequences were compared with WhSMV sequences from GenBank using a BLASTn search. The SDT program was used to determine nucleotide identity, and phylogenetic relationships were established using the MEGA11 software. Analyses were performed on a global dataset that included sequences obtained in this study and sequences previously characterized in South Africa, Paraguay and Brazil. The nucleotide sequences showed an identity ranging from 94% to 100% for the two analyzed regions when subjected to paired analysis. Based on specific primers amplification and aminoacid sequence of CP identity higher than 90% when compared to other isolates, the viral isolate characterized in this study is WhSMV. Phylogenetic analyses revealed two distinct clades. Notably no demarcation was observed between the WhSMV isolate characterized in this study and Brazilian isolates previously characterized, indicating a close relationship between them. This is the first report of WhSMV associated with wheat mosaic disease in Santa Catarina, Brazil.