South American Leaf Blight (SALB), caused by Pseudocercospora ulei, is the most important disease in Hevea brasiliensis grown in South America. This study aimed to evaluate long-term resistance in the field for 11 years in 10 rubber tree genotypes (nine hybrid clones and one primary clone) in a large-scale clonal trial (LSCT) and under controlled and nursery conditions. Resistance was evaluated using two resistance components: type of reaction (TR, ranging from 1 to 6) related to asexual sporulation, and stroma density (ST, ranging from 0 to 4), which is linked to sexual sporulation. Resistance status ranking (RSR) based on the maximum scores of the variables was adapted to classify the genotypes (completely resistant, partially resistant or highly susceptible) over time, and against four indigenous isolates of P. ulei. Eight of the ten clones exhibited partial resistance in the field, and clones FDR 5597, GU 198 and FDR 5788 were more resistant with TR ≤ 4 and ST ≤ 2. These clones were completely resistant in the laboratory/nursery with TR < 3 and ST = 0. Only clone MDF 180 did not exhibit the sexual phase of the pathogen (i.e., ST = 0) in the field or in the nursery. Clones CDC 56 and IAN 873 (control) were highly susceptible, with TR > 5 and ST > 2. In this study, sources of partial resistance were evidenced for the effective management of SALB under conditions of high P. ulei incidence in the Amazon.

南美叶枯病（SALB）是巴西橡胶树最重要的病害，由绿叶假尾蚴引起生长在南美洲。本研究旨在通过大规模克隆试验 (LSCT) 和对照和苗圃条件，评估 10 个橡胶树基因型（9 个杂种克隆和 1 个初级克隆）在田间11 年的长期抗性。使用两种抗性成分评估抗性：与无性孢子形成相关的反应类型（TR，范围从 1 到 6）和与有性孢子形成相关的基质密度（ST，范围从 0 到 4）。基于变量的最大分数的抗性状态排名 (RSR) 被调整为随着时间的推移对基因型（完全抗性、部分抗性或高度易感）进行分类，并针对四个本地P. ulei分离株. 十个克隆中有八个在田间表现出部分抗性，克隆 FDR 5597、GU 198 和 FDR 5788 的抗性更强，TR ≤ 4 且 ST ≤ 2。这些克隆在实验室/苗圃中完全抗性，TR < 3 和 ST = 0。只有克隆 MDF 180 在田间或苗圃中没有表现出病原体的有性期（即 ST = 0）。克隆 CDC 56 和 IAN 873（对照）是高度敏感的，TR > 5 和 ST > 2。在这项研究中，部分抗性来源被证明可以在亚马逊高斑马线虫发病率高的条件下有效管理 SALB 。