Fabio Nascimento da Silva

Apple production in southern Brazil is responsible for all national output. However, production is limited by phytosanitary constraints, particularly European canker (EC), caused by Neonectria ditissima . In this context, understanding the climatic factors associated with the infection and development of EC is essential to support more effective and sustainable management strategies. This study aimed to characterize the spatial and seasonal climatic favourability for N. ditissima infection and the initial development of European canker in some of the most productive high‐altitude apple‐producing regions of southern Brazil using the R _m risk model proposed by Kim and Beresford. The R _m risk model integrates rainfall frequency, precipitation amount, and the average number of daily hours with temperatures between 11°C and 16°C into a dimensionless indicator of climatic favourability, based on historical meteorological data from 2016 to 2024 for some of the most productive high‐altitude apple‐producing regions in southern Brazil. The R _m risk data were aggregated on a monthly scale to assess seasonality, seasonal distribution and interannual variability of climatic risk. Intermediate to high R _m values were observed in some of the most productive high‐altitude apple‐producing regions, including Painel, São Joaquim and Urupema, indicating highly favourable climatic conditions for N. ditissima infection and the initial development of EC. Intermediate to high R _m risk values were predominantly concentrated from autumn through spring, with the highest seasonal mean values generally occurring during spring and autumn. In contrast, the lowest risk levels were observed during summer (December to February), with low interannual variability. This pattern indicates the presence of recurrent seasonal risk periods associated with increased environmental favourability for N. ditissima establishment, spread and early EC development. The results demonstrate that some of the most productive high‐altitude apple‐producing regions exhibit persistent climatic suitability for N. ditissima infection and initial development of EC, reinforcing the relevance of the R _m risk index. Although it should not be interpreted as a direct predictor of disease incidence, it provides a quantitative epidemiological framework for identifying climatic risk patterns and supporting future validation, forecasting and integrated disease management programs in high‐altitude apple‐producing regions of southern Brazil.

Physalis peruviana L. (Cape gooseberry) is susceptible to several pathogens, among which the sobemovirus physalis rugose mosaic virus (PhyRMV) is most prominent. This study investigated the anatomical, morphophysiological, and metabolic responses of P. peruviana to PhyRMV over the course of the infection cycle. P. peruviana plants were grown under greenhouse conditions (24 ± 2 ℃) and mechanically inoculated with buffer (mock) or PhyRMV inoculum. The local and systemic leaves were collected at 0, 3, 7, 14, 21, and 42 days after inoculation (DAI) and viral infection was confirmed by RT-qPCR. Morphological traits, including plant height, symptoms, and the Falker chlorophyll index, and histological changes were evaluated in PhyRMV-infected plants and compared to mock-inoculated controls. To characterize and compare their metabolic profile, the collected leaves were processed and subjected to gas chromatography-mass spectrometry (GC–MS). Yield was also assessed by quantifying the number and weight of fruits. PhyRMV could be detected in systemic leaves from 14 DAI onward, accompanied by an increase in viral load and the intensification of the symptoms, including mosaic, chlorosis, and leaf deformation from 21 DAI onward, which were associated with reduced plant height and chlorophyll contents. At 42 DAI, histological changes and increased starch accumulation were observed in the infected leaves, suggesting impaired photoassimilate transport. GC-MS revealed an accumulation of sucrose, pyruvate, and tricarboxylic acid (TCA) cycle metabolites, possibly due to the high energy demand associated with viral replication, indicating significant alterations in the functioning of the central metabolic pathways in systemic leaves in the late stage of infection at 42 DAI. Compounds such as glutamate, isoleucine, and malonate could potentially be involved in the activation of defense pathways, including the shikimic acid pathway. Metabolic networks demonstrated a loss of complexity in the infected plants, indicating a redirection of resources from primary metabolism to defense-associated mechanisms. Thus, fruit production was reduced by 31% in the infected plants, highlighting a negative impact of infection on the production potential. These results support management strategies based on the induction of plant defense mechanisms and reinforce the importance of the use of integrative approaches to understanding the physiological and biochemical impacts of viruses on crops.

European canker (EC), caused by Neonectria ditissima , is one of the major threats to apple production in temperate and subtropical highland regions, where pruning residues represent an important source of inoculum. This study monitored the temporal dynamics of N. ditissima spore release from whole and shredded branches, with and without visible EC symptoms, obtained from training prunings of ‘Gala’ and ‘Fuji’ apple trees during the 2023–2025 growing seasons in high‐altitude orchards of southern Brazil. Whole and shredded branches were placed separately in spore‐trap boxes, and microscope slides were replaced weekly to quantify airborne ascospores and conidia. Shredding was performed using a hydraulic mower. Ascospores were consistently the dominant spore type, exhibiting higher release magnitude and frequency than conidia across all treatments and both cultivars. Whole symptomatic branches were the most productive inoculum source, displaying the highest ascospores and conidia release peaks, particularly in ‘Gala’. Shredding reduced spore output but did not eliminate inoculum viability, as shredded symptomatic branches continued to release substantial quantities of spores throughout the evaluation period. Whole and shredded asymptomatic branches also released ascospores and conidia, although at lower intensities, suggesting the presence of latent infections and confirming that the absence of visible symptoms does not preclude inoculum production. Spore‐release peaks in all treatments occurred during periods with rainfall, highlighting moisture as a key environmental factor for maturation of perithecia and sporodochia and spore discharge. The superior spore release capacity of ‘Gala’ under all conditions indicates that this cultivar may act as a regional inoculum resource in areas where EC is endemic. These findings underscore the need for improved EC management strategies, particularly regarding pruning‐residue handling. The persistence of viable inoculum in symptomatic and asymptomatic tissues, even after shredding, demonstrates that residue destruction or removal is essential to reduce disease pressure and limit pathogen spread within and between orchards.

Soil-borne wheat mosaic disease (SBWMD), caused by wheat stripe mosaic virus (WhSMV), poses an emerging threat to wheat production in South America. In this study, we analyzed the transcriptomic responses of two Triticum aestivum genotypes exhibiting contrasting resistance levels to WhSMV. The resistant cultivar, Embrapa 16, displayed low viral accumulation and either mild or no symptoms, whereas the susceptible cultivar, BRS Guamirim, exhibited pronounced chlorosis, stunting, and elevated virus titers. RNA-Seq analysis identified 13,225 differentially expressed genes (DEGs) across four genotype-infection contrasts. In Embrapa 16, WhSMV infection resulted in the enrichment of Gene Ontology (GO) terms associated with defense responses, kinase activity, and hormone signaling, with marked induction of genes such as RPP13-like, RGA3, and shikimate kinase. In contrast, BRS Guamirim demonstrated extensive downregulation of photosynthesis-related genes and a disrupted hormonal response, indicating compromised metabolic homeostasis under stress. KEGG and Plant Reactome pathway analyses revealed the activation of MAPK signaling and plant–pathogen interaction pathways in the resistant genotype. These results suggest that effective resistance to WhSMV entails coordinated activation of signaling cascades, secondary metabolism, and chloroplast protection mechanisms, providing molecular insights to inform breeding strategies aimed at durable virus resistance in wheat.

Powdery mildew, caused by the fungus Microsphaera diffusa, reduces the photosynthetically active leaf area of soybean plants, negatively interfering with grain yield. Information on the resistance of soybean cultivars to powdery mildew, crucial for disease management, is scarce and rarely made available by cultivar owners. Ths research evaluated the reaction of soybean cultivars to powdery mildew. The experiments were conducted in a protected environment (greenhouse) during the 2022/23 and 2023/24 seasons, evaluating 48 cultivars. Plant inoculation with M. diffusa was performed at the first node development stage (V1), using two isolates of the fungus from different locations and cultivars. Quantification of powdery mildew incidence and severity was performed at the fifth node stage (V5). The two unifoliate leaves, the first, the second, and the third trifoliate leaves were evaluated. All cultivars tested showed 100% incidence of unifoliate and trifoliate leaves, with no differences between them. The difference was observed in the severity of trifoliate leaves. Of the 48 soybean cultivars tested, none showed resistance to the fungus M. diffusa, with all being classified as susceptible or highly susceptible.

The corn leafhopper, Dalbulus maidis (DeLong & Wolcott) (Hemiptera: Cicadellidae), is a key pest of maize crops in the tropical and subtropical regions of the Americas. In addition to direct damage, its major impact is related to its action as insect vector of pathogens related to corn stunting complex (CSC). CSC diseases are currently the most important and cause severe crop losses in Argentina, Mexico, Brazil, and the southern United States, and outbreaks have been more oftenly reported. Little information is available on the population characteristics of the corn leafhopper and its bioecology. In this sense, we analyzed the genetic diversity of 120 representative specimens of D. maidis from four regions of Brazil (Northeast, Southeast, South, and Central-West) using a region of the mitochondrial gene coding for the cytochrome oxidase subunit I (mtCOI) as molecular marker. In addition, the infectivity of the collected insects with CSC pathogens was assessed to verify the prevalence of each CSC pathogen in specimens collected from different regions of Brazil. The Brazilian D. maidis population studied was divided into 18 mitochondrial haplotypes, focusing on haplotypes A, B, and C, which are predominant in this country. In addition, the mtCOI gene of D. maidis was found to have low variability in Brazil (π = 0.00171). Our data suggest that there are no spatial or temporal barriers between the different populations of D. maidis studied, which could be due to a short evolutionary time and its outstanding dispersion capacity. In addition, this study revealed a prevalence of infected leafhoppers with any of the CSC pathogens in Brazil, with more than half of the samples analyzed carrying at least one of the phytopathogens studied. Our study provides insights on population pest management of D. maidis in order to prevent CSC incidence in maize crops and pest resistance development in these vector populations to agricultural pesticides.