Asian soybean rust (ASR), caused by the fungus Phakopsora pachyrhizi Syd & P. Syd, is the main disease that affects soybean crop in South America. Disease control is based on the use of site-specific fungicides (QoIs, DMIs and SDHIs), multisite fungicides and host-free period. Continuous and intensive use of fungicides has selected isolates of P. pachyrhizi, with reduced sensitivity to DMIs, QoIs and SDHIs. This work includes sensitivity studies for prothioconazole and SDHIs and genetic analysis of target site mutations in P. pachyrhizi related to sensitivity reduction to DMIs, QoIs and SDHIs collected from different regions of soybean production areas. Different CYP51 genotypes with distinct point mutations known to influence DMI sensitivity are present in Brazilian isolates. Combined mutation F120L + Y131H on CYP51 gene was the most frequent among Brazilian isolates. Mutant isolates showed higher EC₅₀ values to the DMI prothioconazole compared to wild type isolates. Regarding QoI, almost all Brazilian isolates carried the mutation F129L in the CYTB gene. Wild type of the SdhC gene was the most frequent genotype to SDHI fungicides, but the mutation leading to the I86F amino acid exchange has also been detected. Such isolates showed higher EC₅₀ values to the SDHIs bixafen, benzovindiflupyr and fluxapyroxad compared to wild type isolates. The most frequent genotype in our collection presented target site mutations in the CYP51 and CYTB genes. A monouredinial isolate with mutations in all three target genes was detected and is here described for the first time. Its current and further spread, and the impact on field performance of fungicides with these modes of action needs further evaluation.

由真菌Phakopsora pachyrhizi Syd＆P. Syd引起的亚洲大豆锈病（ASR）是影响南美大豆作物的主要疾病。疾病控制基于对位点特异性杀菌剂（QoI，DMI和SDHI），多位点杀菌剂和无宿主期的使用。连续和大量使用杀真菌剂已选择了P. pyryrhizi的分离株，这些分离株对DMI，QoI和SDHI的敏感性降低。这项工作包括对原硫代康唑和SDHIs的敏感性研究，以及对P. pyryrhizi中靶位点突变的遗传分析，该突变与降低从大豆产区不同地区收集的DMI，QoIs和SDHIs的敏感性有关。不同的CYP51巴西分离株中存在已知具有影响DMI敏感性的明显点突变的基因型。CYP51基因上的联合突变F120L + Y131H是巴西分离株中最常见的突变。与野生型分离株相比，突变分离株对DMI保硫康唑的EC ₅₀值更高。关于QoI，几乎所有巴西分离株都在CYTB基因中携带F129L突变。SdhC基因的野生型是SDHI杀菌剂的最常见基因型，但也检测到导致I86F氨基酸交换的突变。此类分离物显示出较高的EC ₅₀与野生型分离株相比，SDHIs的bixafen，benzovindiflupyr和fluxapyroxad具有较高的抗药性。我们收集中最常见的基因型在CYP51和CYTB基因中出现靶位点突变。检测到在所有三个靶基因中均具有突变的单尿嘧啶分离株，并在此首次进行了描述。其当前和进一步的传播，以及这些作用方式对杀菌剂对田间性能的影响需要进一步评估。