Tar spot of maize (Zea mays L.), caused by the obligate biotroph Phyllachora maydis Maubl., is an emerging disease in the United States and Canada, and the identification of sources of resistance for tar spot will enable the development of resistant hybrids. In 2019 and 2020, 25 accessions from the germplasm enhancement of maize (GEM) project containing exotic introgressions in elite backgrounds were evaluated in nine environments for tar spot severity. Environmental conditions had a major influence on disease development, as tar spot severity varied across locations with only four of the nine locations showing moderate to high levels of disease. In five environments, disease levels were low and disease severity data was not collected or used. Accessions were visually evaluated for tar spot during reproductive growth stages in three environments and during vegetative growth stages in one environment. There was a strong correlation between resistance to P. maydis across locations where accessions were evaluated in reproductive growth stages. Two accessions, GEMS-0066 and GEMS-0226, were the most resistant and could prove useful for tar spot resistance breeding. These accessions are publicly available and able to be directly used in breeding programs.

中文翻译：

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玉米外来种质中玉米毛霉抗性鉴定

玉米焦油斑 ( Zea mays L.)，由专性生物营养体Phylachora maydis引起Maubl. 是美国和加拿大的一种新出现的疾病，识别焦油斑抗性来源将使抗性杂交种的开发成为可能。在 2019 年和 2020 年，玉米种质增强 (GEM) 项目中的 25 个种质在 9 个环境中评估了焦油斑严重程度，这些种质包含具有优良背景的外来基因渗入。环境条件对疾病发展有重大影响，因为焦油斑的严重程度因地点而异，九个地点中只有四个显示出中度至高度疾病。在五个环境中，疾病水平较低，未收集或使用疾病严重程度数据。在三种环境中的生殖生长阶段和一种环境中的营养生长阶段，目视评估种质的焦油斑。P. maydis在生殖生长阶段评估种质的地点。两个种质 GEMS-0066 和 GEMS-0226 抗性最强，可证明对焦油斑抗性育种有用。这些种质是公开的，可以直接用于育种计划。