The adult plant rust resistance loci Lr34/Yr18 and Lr46/Yr29 are important determinants of partial resistance to powdery mildew in bread wheat line Saar

Abstract

Powdery mildew, caused by Blumeria graminis f. sp. tritici is a major disease of wheat (Triticum aestivum L.) that can be controlled by resistance breeding. The CIMMYT bread wheat line Saar is known for its good level of partial and race non-specific resistance, and the aim of this study was to map QTLs for resistance to powdery mildew in a population of 113 recombinant inbred lines from a cross between Saar and the susceptible line Avocet. The population was tested over 2 years in field trials at two locations in southeastern Norway and once in Beijing, China. SSR markers were screened for association with powdery mildew resistance in a bulked segregant analysis, and linkage maps were created based on selected SSR markers and supplemented with DArT genotyping. The most important QTLs for powdery mildew resistance derived from Saar were located on chromosomes 7DS and 1BL and corresponded to the adult plant rust resistance loci Lr34/Yr18 and Lr46/Yr29. A major QTL was also located on 4BL with resistance contributed by Avocet. Additional QTLs were detected at 3AS and 5AL in the Norwegian testing environments and at 5BS in Beijing. The population was also tested for leaf rust (caused by Puccinia triticina) and stripe rust (caused by P. striiformis f. sp. tritici) resistance and leaf tip necrosis in Mexico. QTLs for these traits were detected on 7DS and 1BL at the same positions as the QTLs for powdery mildew resistance, and confirmed the presence of Lr34/Yr18 and Lr46/Yr29 in Saar. The powdery mildew resistance gene at the Lr34/Yr18 locus has recently been named Pm38. The powdery mildew resistance gene at the Lr46/Yr29 locus is designated as Pm39.

Multiple Quantitative Trait Analysis Using Bayesian Networks

“…This can be explained by the increased susceptibility to one disease in genotypes that are weakened by the onset of the other, by disease resistance being controlled by shared regions in the genome (Spielmeyer et al 2005;Lillemo et al 2008), and to a lesser extent by the influence of weather conditions (Beest et al 2008). The BN in Figure 1 identifies 9 SNPs that are linked to at least one of MIL and YR.GLASS and may be tagging pleiotropic QTL for disease resistance.…”

Advanced Breeding Strategies to Mitigate the Threat of Yellow Stripe Rust of Wheat

“…Many prominent APR genes, such as Lr34/Yr18/ Sr57/Pm38 (Dyck1987; McIntosh 1992; Singh 1992; Spielmeyer et al, 2005;Lillemo et al, 2008;Krattinger et al, 2009), Lr46/Yr29/Sr58/Pm39 (Singh et al,1998;William et al, 2003;Lillemo et al, 2008), Lr67/Yr46/ Sr55/Pm46 (Herrer Foessel et al, 2011;Hiebert et al, 2011), Yr36 , Sr2/Yr30 (Singh et al, 2000;Suenaga et al, 2003), and Lr68 , have been well characterized. Similarly, during the last 15 years, several molecular mapping studies have reported dozens of quantitative trait loci (QTL) distributed throughout all 21 chromosomes for YR resistance, and at least in 20 chromosomes for LR resistance in hexaploid wheat germplasm (Naz et al, 2008;Basnet 2012;Singh 2012 http://wheatatlas.cimmyt.org/country/varieties/ AFG/0).…”

“…Lr34, which has recently been cloned and found to encode an ATP-binding cassette (ABC) transporter of the ABC transporter subfamily G (ABCG), formerly known as pleiotropic drug resistance (PDR) subfamily (Krattinger et al, 2009), is known to confer broad-spectrum resistance to at least four biotrophic diseases: leaf rust (Dyck et al, 1966), stripe rust (Singh, 1992b), stem rust (Dyck, 1987) and powdery mildew (Lillemo et al, 2008;Spielmeyer et al, 2005). Lr34 is also associated with a premature senescence of the leaf tips, commonly referred to as leaf tip necrosis (LTN) (Singh, 1992a).…”

Molecular Detection of the Adult Plant Leaf Rust Resistance GeneLr34in Romanian Winter Wheat Germplasm

“…This gene was described by Dyck (1977), as LrT2, in the cultivar Frontana and was located on short arm of the chromosome 7DS (Dyck 1987). Lr34 or closely linked genes was found to provide resistance to two other rust diseases ) and powdery mildew (Spielmeyer et al 2005;Lillemo et al 2008). Recently, this locus has been also shown to provide resistance to spot blotch caused by Bipolaris sorokiniana (Lillemo et al 2013).…”