Identification of novel genomic regions associated with resistance to Pyrenophora tritici-repentis races 1 and 5 in spring wheat landraces using association analysis

Abstract

Tan spot, caused by Pyrenophora tritici-repentis, is a major foliar disease of wheat worldwide. Host plant resistance is the best strategy to manage this disease. Traditionally, bi-parental mapping populations have been used to identify and map quantitative trait loci (QTL) affecting tan spot resistance in wheat. The association mapping (AM) could be an alternative approach to identify QTL based on linkage disequilibrium (LD) within a diverse germplasm set. In this study, we assessed resistance to P. tritici-repentis races 1 and 5 in 567 spring wheat landraces from the USDA-ARS National Small Grains Collection (NSGC). Using 832 diversity array technology (DArT) markers, QTL for resistance to P. tritici-repentis races 1 and 5 were identified. A linear model with principal components suggests that at least seven and three DArT markers were significantly associated with resistance to P. tritici-repentis races 1 and 5, respectively. The DArT markers associated with resistance to race 1 were detected on chromosomes 1D, 2A, 2B, 2D, 4A, 5B, and 7D and explained 1.3-3.1% of the phenotypic variance, while markers associated with resistance to race 5 were distributed on 2D, 6A and 7D, and explained 2.2-5.9% of the phenotypic variance. Some of the genomic regions identified in this study correspond to previously identified loci responsible for resistance to P. tritici-repentis, offering validation for our AM approach. Other regions identified were novel and could possess genes useful for resistance breeding. Some DArT markers associated with resistance to race 1 also were localized in the same regions of wheat chromosomes where QTL for resistance to yellow rust, leaf rust and powdery mildew, have been mapped previously. This study demonstrates that AM can be a useful approach to identify and map novel genomic regions involved in resistance to P. tritici-repentis.

Mapping QTL for resistance againstPyrenophora tritici-repentisin wheat

“…Furthermore Arseniuk et al (2004) also found a region associated with resistance to Stagonospora nodorum blotch in seedlings to a mixed isolate in chromosome 6AL. However, in a study using 567 landraces, markers associated with resistance to race 1 and 5 isolates were found in a similar region as the QTL in this work, on the short arm of chromosome 6A (Gurung et al 2011).…”

Evaluation and Association Mapping of Resistance to Tan Spot and Stagonospora Nodorum Blotch in Adapted Winter Wheat Germplasm

“…These regions may also correspond to major resistance QTL previously identified in segregating biparental populations (Chu et al 2008b, Faris andSingh et al 2008;Tadesse et al 2007). Gurung et al (2011) identified genomic regions on chromosomes 1D, 2A, 2B, 2D, 4A, and 7D for Pti2 and genomic regions on chromosomes 2D, 6A, and 7D for race 5 in a worldwide spring wheat core collection. We also identified genomic regions on chromosomes 2D and 4A with isolate Pti2 but no common QTL was identified for DW5.…”

“…Several studies have been done to map resistance to the two diseases using the association mapping approach Gurung et al 2011;Kollers et al 2014;Patel et al 2013;Tommasini et al 2007). Because different marker types (simple sequence repeat or diversity arrays technology) have been used, it is difficult to compare Table 4.…”

Genome-Wide Association Studies Identifies Seven Major Regions Responsible for Iron Deficiency Chlorosis in Soybean (Glycine max)

“…The germplasm is expected to be narrow given the limited range of maturity group (0–1), the short history of soybean breeding in USA, and the limited number of traits selected in the breeding programs. Here we used multiple mixed models [31], [34], [43]–[45] that control for confounding effect of population structure and population relatedness [16], [46].…”