Biology subjects

Alves Santos de Oliveira, S.

Publications and source records attributed to Alves Santos de Oliveira, S..

2 recordsLinked to original sources

bioRxiv2025

Phenotypic and Genotypic Characterization of the Population of Phytophthora infestans in Brazil

Recently, phenotypic variations and differences in virulence have been observed among Brazilian isolates of P. infestans. Analysis of phenotypic variability can be useful to understand the pathogen population and how variants may affect late blight epidemics. Thus, this study aimed to characterize the population of P. infestans in Brazil using mating type, mitochondrial DNA haplotype, microsatellite genotype, and mefenoxam sensitivity. Isolates of the A2 mating type from tomato are reported for the first time. Isolates from potato plants were either of A1 or A2 mating types. The Ia and Ib mitochondrial DNA haplotypes were detected in Brazil. The Ia is associated with isolates from potato and the Ib with isolates obtained from potato and tomato. All tomato isolates were of a new genotype, SA_1_A2, while the EU_37_A2 and EU_2_A1 genotypes were detected among isolates sampled from potato fields. The sensitivity to mefenoxam varied: sensitive, intermediately insensitive, and insensitive isolates are present in potato and tomato crops. The population of P. infestans in Brazil remains structured according to host, but genotypes associated with potato or tomato plants seem to vary periodically.

plant biology↗

bioRxiv2025

Rhizoctonia theobromae associated with a severe witches' broom outbreak in cassava of the Brazilian rainforest and evidence of its Southeast Asian origin

Cassava witches broom disease (CWBD) has emerged as a significant threat to cassava production in the Oiapoque region of Amapa, Brazil. Diseased plants exhibit stunted growth, vascular necrosis, abnormal shoot proliferation, and distinctive broom-like appearance. This study aimed to characterize the disease and identify its causal agent(s). The assessment by high-throughput sequencing of total nucleic acids (DNA and RNA) from affected cassava tissues revealed Rhizoctonia theobromae (syn. Ceratobasidium theobromae) associated with CWBD. PCR-based detection using species-specific primers confirmed the presence of R. theobromae in 74% of symptomatic samples. Genetic diversity analysis based on the Ca2+/calmodulin-dependent protein kinase gene showed low variability among Brazilian isolates compared with Asian populations, suggesting their recent introduction. This first report of R. theobromae causing CWBD in Brazil follows a recent report of the disease from French Guiana and highlights the urgent need for effective measures to prevent the further spread of this emerging pathogen, which poses a deadly threat to cassava cultivation in the rainforest, a significant risk to cassava production in Brazil, and regions with similar eco-climatic conditions.

pathology↗