Lettuce downy mildew caused by Bremia lactucae is one of the main diseases in high humidity and low temperature conditions. The identification of virulence factors appearing in the pathogen population could help improve breeding programs against this disease. This study aimed to monitor and evaluate virulence dynamic changes in B. lactucae virulence among two Brazilian regions to recommend resistance genes for breeding programs. Isolates from São Paulo, Rio Grande do Sul, and Paraná states were assessed using the sextet code EU-C composed by 16 Lactuca spp. genotypes, between 2015 and 2016. To understand the population dynamics, the frequencies of virulence phenotypes and factors and the virulence complexity per isolate (C_i), phenotype (C_p), and Gleason (I_g), indexes were calculated. B. lactucae virulence from Paraná, Rio Grande do Sul and São Paulo were similar and shared nine out of the 15 evaluated virulence factors. In total, 90 isolates were analyzed, and 27 virulence phenotypes were found. The most frequent sextet codes were 31–00-00, 31–00-02, 31–01-00, and 31–01-02. The genes or resistance factors present in ‘Argelès’ (Dm38), ‘Balesta’, and ‘Bartoli’ could be used as sources of resistance by Brazilian lettuce breeders.

乳酸布鲁米氏菌引起的莴苣霜霉病是高湿度和低温条件下的主要疾病之一。对病原体种群中出现的毒力因子的鉴定可以帮助改善针对该疾病的育种程序。这项研究旨在监测和评估两个巴西地区乳酸杆菌的毒力动态变化，以向育种计划推荐抗性基因。对圣保罗，南里奥格兰德州和巴拉那州的分离株进行了评估，使用了16个Lactuca spp组成的六重编码EU-C 。基因型，2015年至2016年。了解种群动态，毒力表型和因子的频率以及每个分离株的毒力复杂性（C _i），表型（C _p）和格里森（I _g），计算指标。来自巴拉那州，南里奥格兰德州和圣保罗的B. lactucae毒力相似，在15个评估毒力因子中共有9个。总共分析了90种分离物，发现了27种毒力表型。最常见的六音码是31–00-00、31–00-02、31–01-00和31–01-02。巴西生菜育种者可以将“Argelès”（Dm 38），“ Balesta”和“ Bartoli”中存在的基因或抗性因子用作抗性来源。