Black Sigatoka, caused by Pseudocercospora fijiensis, is a major foliar disease of banana and plantain worldwide. There are few available data regarding the genetic diversity and population structure of the pathogen in East Africa, which are needed to design effective and durable disease management strategies. We genotyped 319 single-spore isolates of P. fijiensis collected from seven regions in Uganda and Tanzania and five isolates from Nigeria using 16 simple sequence repeat markers and mating type-specific primers. Isolates from each country and region within the country were treated as populations and subpopulations, respectively. A total of 296 multilocus genotypes (MLGs) were recovered, representing a clonal fraction of 7%. Subpopulations had a moderate level of genetic diversity (H_exp = 0.12 to 0.31; mean, 0.29). Mating type distribution did not deviate from equilibrium (MAT1-1: MAT1-2, 1:1 ratio) in Uganda; however, in Tanzania the mating types were not in equilibrium (4:1 ratio). The index of association tests (I_A and r̄_d) showed that all populations were at linkage equilibrium (P > 0.05), thus supporting the hypothesis of random association of alleles. These findings are consistent with a pathogen that reproduces both clonally and sexually. Low and insignificant levels of population differentiation were detected, with 90% of the variation occurring among isolates within subpopulations. The high intrapopulation variation has implications in breeding for resistance to P. fijiensis because isolates differing in aggressiveness and virulence are likely to exist over small spatial scales. Diverse isolates will be required for resistance screening to ensure selection of banana cultivars with durable resistance to Sigatoka in East Africa.

Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

由斐济假单胞菌（Pseudocercospora fijiensis）引起的黑Sigatoka是全世界香蕉和车前草的主要叶面疾病。关于东非病原体的遗传多样性和种群结构的可用数据很少，这对于设计有效和持久的疾病管理策略是必需的。我们对P的319个单孢子分离株进行了基因分型。斐济使用16个简单的序列重复标记和交配类型特异性引物，从乌干达和坦桑尼亚的7个地区和尼日利亚的5个分离株中收集到毒株。来自每个国家和地区的分离株分别被视为人口和亚群。总共回收了296个多基因座基因型（MLG），占克隆比例为7％。亚群具有中等水平的遗传多样性（H _exp = 0.12至0.31；平均值为0.29）。乌干达的交配类型分布没有偏离平衡（MAT1-1：MAT1-2，1：1比例）；但是，在坦桑尼亚，交配类型不平衡（比例为4：1）。的关联测试（索引我_甲和- [R _d）表明所有种群均处于连锁平衡状态（P > 0.05），从而支持了等位基因随机关联的假设。这些发现与克隆繁殖和有性繁殖的病原体一致。检测到的种群分化水平较低且微不足道，其中90％的变异发生在亚种群的分离株之间。高种群内变异对耐P的育种具有重要意义。斐济（Fijiensis），因为侵略性和毒力不同的分离株可能会在较小的空间尺度上存在。筛选抗性将需要各种分离物，以确保选择对东非Sigatoka具有持久抗性的香蕉品种。

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