Interactions among genes Sr2/Yr30, Lr34/Yr18/Sr57 and Lr68 confer enhanced adult plant resistance to rust diseases in common wheat (Triticum aestivum L.) line ‘Arula’

Abstract

Common wheat line Arula displays an acceptable level of adult plant resistance (APR) to stripe rust (YR), leaf rust (LR) and stem rust (SR) in Mexico, and to SR (Ug99 races) in Kenya. Present study was conducted to identify genetic loci that confer resistance in Arula and to understand their interactions for rust resistance. A recombinant inbred line (RIL) population (190 lines) developed from the cross of Arula with susceptible parent Apav was phenotyped under artificially created epidemics of the three rusts in 2014, 2015 and 2016 in Mexico, and for stem rust (Ug99) during the off and main seasons of 2015 in Kenya. The RIL population and parents were genotyped with Sr2/Yr30-linked simple sequence repeat (SSR) marker gwm533 and two sequence tagged site (STS) markers (Lr34/Yr18/Sr57-csLV34 and Lr68-csGS) in addition to genotyping using Illumina iSelect 90K SNP array. A genetic map of 2,634 polymorphic markers (2,631 SNPs, 1 SSR and 2 STS markers) was constructed to locate the resistance loci. Composite interval mapping (CIM) was conducted to identify quantitative trait loci (QTL) associated with rust resistance using phenotypic and genotypic data in Windows QTL cartographer version 2.5. Two consistent QTL contributed by Arula were detected on chromosomes 3BS and 7DS, which corresponded to the previously known APR genes Sr2/Yr30 and Lr34/Yr18/Sr57, respectively. Sr2/Yr30 explained 1.1-14.7% and 41.0-61.5% of the phenotypic variation for YR and SR, respectively; whereas Lr34/Yr18/Sr57 accounted for 22.5-78.0%, 40.0-84.3% and 13.8-24.8% of the phenotypic variation for YR, LR and SR, respectively. Arula was also found to carry the positive allele for marker csGS closely linked to gene Lr68 on chromosome 7BL, although this gene was not detected using CIM. Based on presence or absence of identified genes/QTLs, lines were classified into different groups and t-tests were used to compare the mean relative area under disease progress curve (relAUDPC) over years of different gene combinations. RILs carrying both Lr34/Yr18/Sr57 and Lr68 showed significantly higher APR to LR showing the benefit of gene combination Lr34/Yr18/Sr57 + Lr68. Our results show that RILs possessing both Sr2/Yr30 and Lr34/Yr18/Sr57 had significantly enhanced APR to all three rusts in field trials conducted in Mexico and Kenya. Strategic utilization of these two pleiotropic, multi-pathogen resistance genes with other minor genes is recommended to develop durable rust resistant wheat cultivars.

Genome-Wide Association Studies in Diverse Spring Wheat Panel for Stripe, Stem, and Leaf Rust Resistance

“…The involved genes provide non-race-specific partial resistance to all the pathotypes of a given pathogen species, thus making it more durable (Lagudah, 2011;Burdon et al, 2014). Despite the fact that incorporating APR into new cultivars can be difficult when compared to ASR, it was found that many wheat cultivars possessing APR showed durable resistance (Mcintosh, 1992;Boyd, 2005;Navabi et al, 2005;Singh et al, 2005;Ren et al, 2012b;Chen, 2013;Randhawa et al, 2018). Some APR genes when used in combinations have been known to possess durable pleiotropic resistance against multiple wheat rusts and powdery mildew, i.e., Lr34/Yr18/Sr57/Pm38 (on chromosome 7DS), Lr46/Yr29/Sr58/Pm39 (on chromosome 1BL), and Lr67/Yr46/Sr55/Pm46 (on chromosome 4DL) (Lagudah, 2011;Risk et al, 2012;Ellis et al, 2014), of which Lr34 has been studied extensively in different crops including rice, barley, maize, and sorghum (Krattinger et al, 2013(Krattinger et al, , 2019.…”

Mapping QTL Associated with Stripe Rust, Leaf Rust, and Leaf Spotting in a Canadian Spring Wheat Population

“…Both parents used in this study, 'Peace' and 'Carberry', are moderately resistant to stripe rust (Alberta Seed Guide, 2018) and confer rust resistance due to Lr34/Yr18, but additionally each carry unique resistance genes. Several studies have used quantitative trait locus (QTL) mapping to identify markers and chromosome regions influencing disease resistance (Ren et al, 2017;Windju et al, 2017;Randhawa et al, 2018;Zhang et al, 2018). Quantitative trait locus analysis is an effective first step into the discovery of markers that are tightly linked to gene(s) controlling important traits (Singh et al, 2014).…”

Progress in breeding for resistance to Ug99 and other races of the stem rust fungus in CIMMYT wheat germplasm

“…Sr55 (= Lr67/Yr46/Pm46), Sr57 (= Lr34/Yr18/Pm38/Sb1/Bdv1) and Sr58 (= Lr46/ Yr29/Pm39), conferring multi-pathogen resistance [73][74][75][76] were identified in CIMMYT wheat germplasm and used in marker assisted selection (Table 3) [77][78][79][80] . These genes in combination with other APR genes confer enhanced APR to the three rusts [81] . Several mapping studies using CIMMYT semidwarf wheat cultivars showing high levels of resistance to the Ug99 race group indicated the presence of three to five quantitative trait loci conferring APR [82][83][84] .…”