Abstract
Gray leaf spot (GLS), caused by different species of Cercospora, is a fungal, non-soil-borne disease that causes serious reductions in maize yield worldwide. The identification of major quantitative trait loci (QTLs) for GLS resistance in maize is essential for developing marker-assisted selection strategies in maize breeding. Previous research found a significant difference (P < 0.01) in GLS resistance between T32 (highly resistant) and J51 (highly susceptible) genotypes of maize. Initial QTL analysis was conducted in an F2 : 3 population of 189 individuals utilizing genetic maps that were constructed using 181 simple sequence repeat (SSR) markers. One QTL (qGLS8) was detected, defined by the markers umc1130 and umc2354 in three environments. The qGLS8 QTL detected in the initial analysis was located in a 51.96-Mb genomic region of chromosome 8 and explained 7.89–14.71% of the phenotypic variation in GLS resistance in different environments. We also developed a near isogenic line (NIL) BC3F2 population with 1,468 individuals and a BC3F2-Micro population with 180 individuals for fine mapping. High-resolution genetic and physical maps were constructed using six newly developed SSRs. The QTL-qGLS8 was narrowed down to a 124-kb region flanked by the markers ym20 and ym51 and explained up to 17.46% of the phenotypic variation in GLS resistance. The QTL-qGLS8 contained seven candidate genes, such as an MYB-related transcription factor 24 and a C3H transcription factor 347), and long intergenic non-coding RNAs (lincRNAs). The present study aimed to provide a foundation for the identification of candidate genes for GLS resistance in maize.
Highlights
Gray leaf spot (GLS), caused by different species of Cercospora, is a serious foliar disease of maize (Zea mays L.) globally, especially in the Americas and Africa (Ward et al, 1999; Crous and Braun, 2003; Crous et al, 2006)
The present study provides new information on genetic markers for GLS resistance in maize that can be utilized for marker-assisted selection (MAS) breeding and provides a foundation for studying the functional role of candidate genes associated with GLS resistance in maize
GLS resistance in the T32 parent was significantly higher than it was in the J51 parent
Summary
Gray leaf spot (GLS), caused by different species of Cercospora, is a serious foliar disease of maize (Zea mays L.) globally, especially in the Americas and Africa (Ward et al, 1999; Crous and Braun, 2003; Crous et al, 2006). GLS was first identified in Asia in 2007 in Nepal (Manandhar et al, 2011). It occurs in the spring production regions of maize in northeast China (Li and Mei, 2008) and. Fine Mapping QTL-qGSL8 in Maize has spread to the north, east, and southwest of China over the past 20 years. It has surpassed the occurrence of maize big spots in the Yunnan, Sichuan, and Hubei provinces of China and has become the most important leaf disease (Zhou et al, 2012). Previous studies have reported yield reductions of 260–320 kg/hm due to outbreaks of GLS (Engelsing et al, 2012)
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