Department of Plant and Soil Sciences, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, South Africa.
Department of Biochemistry, Genetics and Microbiology, FABI, University of Pretoria, South Africa.
Fungal Genet Biol. 2021 Apr;149:103527. doi: 10.1016/j.fgb.2021.103527. Epub 2021 Jan 30.
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.
玉米叶斑病是非洲玉米灰斑病的病原菌。该真菌病原体在南非表现出高度的遗传多样性。然而，人们对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，我们旨在评估主要东非和南部非洲（肯尼亚、乌干达、赞比亚、津巴布韦和南非）玉米生产国之间病原体的多样性和基因流。从灰斑病病斑中分离出 964 个单孢子分离物，并通过 PCR 诊断确认为 C.zeina。不存在灰斑病的另一个病原菌，即 Cercospora zeae-maydis。使用 11 个微卫星标记和交配型基因诊断对所有 C.zeina 分离物进行基因分型，结果显示：（i）五个非洲国家之间存在高度遗传多样性和一些种群结构；（ii）隐性有性重组；（iii）南非和肯尼亚是最大的移民来源地；（iv）赞比亚有一个独特的种群。我们注意到有人类介导的长距离扩散的证据，因为来自南非一个地点的四个单倍型也存在于肯尼亚和乌干达的五个地点。没有证据表明病原体有单一的进入非洲的入口。南非是肯尼亚、乌干达和津巴布韦种群最有可能的起源地。在热带地区（肯尼亚和乌干达）进行连续的年度玉米生产并没有比在南非进行一个玉米季节产生更高的遗传多样性。我们的研究结果将通过对毒力 C.zeina 菌株的有效监测，为未来在非洲管理灰斑病提供依据。
