QTL mapping for resistance of maize to grey leaf spot

Abstract

Grey leaf spot (GLS) is a global maize leaf disease that seriously endangers maize production. Discovering and utilizing genetic loci for GLS resistance would be useful for breeding new varieties with improved resistance. In this study, 233 F2:3 families (produced from the susceptible inbred line 08‐641 × the resistant inbred line 446) were used for quantitative trait locus (QTL) mapping of resistance to GLS. Five GLS resistance QTLs were detected on chromosomes 1, 2, 3, 4, and 6, which explained 6.7%‐21.3% of the phenotypic variation. The QTLs, qRgls.CH‐4, qRgls.CH‐1, qRgls.CH‐2, and qRgls.CH‐6, were stably expressed in the four environments, and all loci for GLS resistance were derived from the resistant parent, 446. The additive effects of qRgls.CH‐4, qRgls.CH‐1, and qRgls.CH‐6 were significantly greater than their single dominant effects, which may be beneficial for GLS resistance breeding. The QTL qRgls.CH‐6, located in bins 6.02–6.05, did not overlap with any previously reported resistance QTL and thus was identified here for the first time. QTL analysis of PI (leaf performance index) detected three leaf function QTLs on chromosomes 4, 8, and 9 were related to GLS resistance and explained 4.8%‐6.2% of the phenotypic variation. Among them, qPI.CH‐4 was significantly stronger expressed in several environments; this allele associated with increased leaf function came from the resistant parent, 446, and its interval overlapped with that of qRgls.CH‐4. Furthermore, both qRgls.CH‐4 and qPI.CH‐4 were located in a hotspot area for GLS resistance in bins 4.05‐4.06, indicating that GLS resistance was significantly related to leaf performance and that GLS significantly reduced leaf photosynthetic performance.

Genetic Dissection of Resistance to Gray Leaf Spot by Combining Genome-Wide Association, Linkage Mapping, and Genomic Prediction in Tropical Maize Germplasm

“…Maize is the most important cereal crop in sub-Saharan Africa (SSA), where more than 80% of the population rely on it as a source of food, income, and livelihood (Prasanna et al, 2020). Gray leaf spot (GLS) is a one of the major foliar diseases of maize caused by the polycyclic pathogens Cercospora zeae-maydis and Cercospora zeina (Crous et al, 2006;He et al, 2018). In eastern Africa, C. zeae-maydis is more prevalent.…”

“…Quantitative trait loci (QTLs) underlying resistance to several diseases in maize have been identified in the last two decades (Welz and Geiger, 2000;Shi et al, 2014;Xu et al, 2014;de Jong et al, 2018;He et al, 2018;Sitonik et al, 2019;Du et al, 2020;Lv et al, 2020). Despite the substantial number of QTLs reported, majority of them had huge confidence intervals, which represented large segments of chromosomes.…”

“…Although a biparental population-based genetic mapping approach offers high QTL detection power, the resolution remains low (Holland, 2007). In recent QTL mapping studies, the size of the mapping populations usually ranged between 100 and 300 individuals (Lehmensiek et al, 2001;Zwonitzer et al, 2010;Berger et al, 2014;He et al, 2018).…”

Transcriptomic Analysis Reveals Candidate Genes Responding Maize Gray Leaf Spot Caused by Cercospora zeina

“…In previous QTL-mapping, four GLS-resistance QTLs (qRgls.CH-1, qRgls.CH-2, qRgls.CH-4, and qRgls.CH-6) were identified in different chromosomes [49]. Candidate DEGs identified from RNA-seq that were consistently located in the QTL interval were considered consensus genes, which were more reliable for further analysis.…”

Multi‐parental QTL mapping of resistance to white spot of maize (Zea mays) in southern Brazil and relationship to QTLs of other foliar diseases

“…The pathogens causing GLS are necrotrophic fungi that produce greyish rectangular lesions on maize leaves. Disease development is favoured by warm (around 27 C) and wet (>90% relative humidity) weather conditions (He et al, 2018;Lennon et al, 2016). NCLB is caused by the hemibiotrophic fungus Exserohilum turcicum [Pass.]…”