Abstract
Leaf rust, caused by the fungus Puccinia triticina Erikss (Pt), is a destructive disease affecting wheat (Triticum aestivum L.) and a threat to food security. Developing resistant cultivars represents a useful method of disease control, and thus, understanding the genetic basis for leaf rust resistance is required. To this end, a comprehensive bibliographic search for leaf rust resistance quantitative trait loci (QTL) was performed, and 393 QTL were collected from 50 QTL mapping studies. Afterward, a consensus map with a total length of 4,567 cM consisting of different types of markers (simple sequence repeat [SSR], diversity arrays technology [DArT], chip-based single-nucleotide polymorphism [SNP] markers, and SNP markers from genotyping-by-sequencing) was used for QTL projection, and meta-QTL (MQTL) analysis was performed on 320 QTL. A total of 75 MQTL were discovered and refined to 15 high-confidence MQTL (hcmQTL). The candidate genes discovered within the hcmQTL interval were then checked for differential expression using data from three transcriptome studies, resulting in 92 differentially expressed genes (DEGs). The expression of these genes in various leaf tissues during wheat development was explored. This study provides insight into leaf rust resistance in wheat and thereby provides an avenue for developing resistant cultivars by incorporating the most important hcmQTL.
Highlights
Leaf rust, caused by the fungal pathogen Puccinia triticina Erikss (Pt), causes a significant reduction in grain yield worldwide, and it is considered a disease with significant importance in wheat (Triticum aestivum L.) (Roelfs et al 1992; Khan et al 2013; Kolmer, 2005)
Before projecting onto the consensus map, a confidence interval (CI) of 95% was homogenized across the different studies using the following formulas: 530/(N x PVE) for F2:3, 163/(N x PVE) for recombinant inbred lines (RILs) and 287/(N x PVE) for DH (Darvasi and Soller, 1997; Guo et al 2006), where N is the number of genotypes in the mapping population, and PVE is the phenotypic variance explained by the Quantitative trait loci (QTL)
A feature of the consensus map and QTL database was that the B genome reported the highest marker saturation, and the highest number of QTLs was mapped to this genome, which is in agreement with previous studies characterizing genetic diversity and unravelling complex traits for disease resistance in bread wheat (Li et al 2015; Soriano and Royo, 2015; Wang et al 2014)
Summary
Leaf rust, caused by the fungal pathogen Puccinia triticina Erikss (Pt), causes a significant reduction in grain yield worldwide, and it is considered a disease with significant importance in wheat (Triticum aestivum L.) (Roelfs et al 1992; Khan et al 2013; Kolmer, 2005). Compared to other fungal rust diseases, such as stem and stripe rust, leaf rust occurs more frequently and has a wider distribution (Bolton et al 2008). This wide spread of leaf rust may be because the spores of P. triticina are transported long distances via wind or humans, thereby causing damage to wheat crops outside their environment or country of origin, as has been observed in various studies in North America (Olmer and Kolmer, 2005; Bolton et al 2008; Brown and Hovmøll, 2008). There is a need to detect the most promising consensus QTL found among studies using different parents that is stable across environments
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