Quantitative detection of Exserohilum turcicum in northern leaf blight diseased sorghum and maize leaves
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Quantitative detection of Exserohilum turcicum in northern leaf blight diseased sorghum and maize leaves B. Langenhoven 1 & S. L. Murray 2 & B. G. Crampton 1 Received: 3 April 2020 / Accepted: 30 July 2020 # Australasian Plant Pathology Society Inc. 2020
Abstract Exserohilum turcicum is the causal agent of northern leaf blight (NLB) disease in sorghum and maize. Early detection of this economically important pathogen is essential for effective disease management to limit yield losses. Here we present a real-time quantitative PCR (qPCR) assay specific for E. turcicum detection and biomass quantification in sorghum and maize. In planta fungal quantification was achieved through amplification of a cytochrome P450 oxidoreductase (cpr1) gene fragment and subsequent normalisation to the host glutathione S-transferase III gene (gst3). The assay could specifically detect E. turcicum in sorghum and maize, but the cpr1 gene fragment was not amplified in non-target fungal pathogens. Application of the assay with NLB diseased sorghum and maize leaf material revealed a significant increase in E. turcicum DNA in leaves with lesion symptoms when compared to leaves with early stage chlorotic fleck symptoms in both hosts. Furthermore, E. turcicum was detected at levels as low as 1 pg in infected sorghum and maize leaves. The assay enables rapid detection and quantification of E. turcicum in sorghum and maize and has useful applications in crop breeding programmes and disease management where cultivar selection and early detection of the pathogen are essential to limit disease spread. Keywords Exserohilum turcicum . Fungal biomass . Northern leaf blight . qPCR . Real-time quantitative PCR
Introduction Maize (Zea mays L.) and sorghum (Sorghum bicolor (L.) Moench) are considered the third and fifth most important cereal crops grown globally (FAOSTAT 2017). Maize is the most important grain crop in South Africa, and is a major dietary staple as well as a good source for animal feed and biofuel production (Department of Agriculture 2018). Sorghum is a drought and heat tolerant crop and therefore highly beneficial in hot, dry areas where other cereal crops do not produce sufficient yields. Sorghum is therefore a vital Electronic supplementary material The online version of this article (https://doi.org/10.1007/s13313-020-00733-5) contains supplementary material, which is available to authorized users. * B. G. Crampton [email protected] 1
Department of Plant and Soil Sciences, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Hatfield 0002, South Africa
2
Department of Molecular and Cell Biology, University of Cape Town, Rondebosch 7700, South Africa
staple for populations in semi-arid regions such as Africa and Asia (Du Plessis 2008). One of the major factors influencing the yield of maize and sorghum is pathogen infection. Exserohilum turcicum (Pass.) Leonard & Suggs (sexual stage: Setosphaeria turcica) is a hemibiotrophic fungal pathogen that causes northern leaf blight
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