Cercospora zeina is a causal pathogen of gray leaf spot (GLS) disease of maize in Africa. This fungal pathogen exhibits a high genetic diversity in South Africa. However, little is known about the pathogen’s population structure in the rest of Africa. In this study, we aimed to assess the diversity and gene flow of the pathogen between major maize producing countries in East and Southern Africa (Kenya, Uganda, Zambia, Zimbabwe, and South Africa). A total of 964 single-spore isolates were made from GLS lesions and confirmed as C. zeina using PCR diagnostics. The other causal agent of GLS, Cercospora zeae–maydis, was absent. Genotyping all the C. zeina isolates with 11 microsatellite markers and a mating-type gene diagnostic revealed (i) high genetic diversity with some population structure between the five African countries, (ii) cryptic sexual recombination, (iii) that South Africa and Kenya were the greatest donors of migrants, and (iv) that Zambia had a distinct population. We noted evidence of human-mediated long-distance dispersal, since four haplotypes from one South African site were also present at five sites in Kenya and Uganda. There was no evidence for a single-entry point of the pathogen into Africa. South Africa was the most probable origin of the populations in Kenya, Uganda, and Zimbabwe. Continuous annual maize production in the tropics (Kenya and Uganda) did not result in greater genetic diversity than a single maize season (Southern Africa). Our results will underpin future management of GLS in Africa through effective monitoring of virulent C. zeina strains.

Cercospora zeina是非洲玉米灰叶斑病 (GLS) 病害的病原体。这种真菌病原体在南非表现出很高的遗传多样性。然而，对该病原体在非洲其他地区的种群结构知之甚少。在这项研究中，我们旨在评估东部和南部非洲（肯尼亚、乌干达、赞比亚、津巴布韦和南非）主要玉米生产国之间病原体的多样性和基因流。总共 964 个单孢子分离株从 GLS 病变中分离出来，并使用 PCR 诊断方法确认为C.  zeina。不存在GLS 的另一种致病因子玉米尾孢-玉米螟。对所有C. zeina 进行基因分型 具有 11 个微卫星标记和交配型基因诊断的分离株显示 (i) 五个非洲国家之间具有某些人口结构的高遗传多样性，(ii) 隐秘的性重组，(iii) 南非和肯尼亚是最大的移民捐助国，以及 (iv) 赞比亚有一个独特的人口。我们注意到人类介导的长距离传播的证据，因为来自一个南非站点的四种单倍型也存在于肯尼亚和乌干达的五个站点。没有证据表明病原体进入非洲的单一入口点。南非是肯尼亚、乌干达和津巴布韦人口最可能的起源地。热带地区（肯尼亚和乌干达）连续年产玉米并没有比单一玉米季节（南部非洲）带来更大的遗传多样性。C.  zeina菌株。