Lr67/Yr46 confers adult plant resistance to stem rust and powdery mildew in wheat

Abstract

We demonstrate that Lr67/Yr46 has pleiotropic effect on stem rust and powdery mildew resistance and is associated with leaf tip necrosis. Genes are designated as Sr55, Pm46 and Ltn3 , respectively. Wheat (Triticum aestivum) accession RL6077, known to carry the pleiotropic slow rusting leaf and yellow rust resistance genes Lr67/Yr46 in Thatcher background, displayed significantly lower stem rust (P. graminis tritici; Pgt) and powdery mildew (Blumeria graminis tritici; Bgt) severities in Kenya and in Norway, respectively, compared to its recurrent parent Thatcher. We investigated the resistance of RL6077 to stem rust and powdery mildew using Avocet × RL6077 F6 recombinant inbred lines (RILs) derived from two photoperiod-insensitive F3 families segregating for Lr67/Yr46. Greenhouse seedling tests were conducted with Mexican Pgt race RTR. Field evaluations were conducted under artificially initiated stem rust epidemics with Pgt races RTR and TTKST (Ug99 + Sr24) at Ciudad Obregon (Mexico) and Njoro (Kenya) during 2010-2011; and under natural powdery mildew epiphytotic in Norway at Ås and Hamar during 2011 and 2012. In Mexico, a mean reduction of 41 % on stem rust severity was obtained for RILs carrying Lr67/Yr46, compared to RILs that lacked the gene, whereas in Kenya the difference was smaller (16 %) but significant. In Norway, leaf tip necrosis was associated with Lr67/Yr46 and RILs carrying Lr67/Yr46 showed a 20 % reduction in mean powdery mildew severity at both sites across the 2 years of evaluation. Our study demonstrates that Lr67/Yr46 confers partial resistance to stem rust and powdery mildew and is associated with leaf tip necrosis. The corresponding pleiotropic, or tightly linked, genes, designated as Sr55, Pm46, and Ltn3, can be utilized to provide broad-spectrum durable disease resistance in wheat.

Adult plant resistance of selected Kenyan wheat cultivars to leaf rust and stem rust diseases

“…To date, more than five APR genes have been identified and validated by several studies (Sr2/Yr30/Lr27/Pbc1, Sr55/Lr67/Yr46/Pm46/Ltn3, Sr57/Lr34/Yr18/Pm38/ Ltn1, Sr58/Lr46/Yr29/Pm39/Ltn2 and Lr68) and confer resistance not only to stem rust but also to other diseases such as leaf rust, yellow rust and powdery mildew of wheat (William et al 2006;Lillemo et al 2008;Krattinger et al 2009;Herrera-Foessel et al 2011;Mago et al 2011a;Herrera-Foessel et al 2014;Kolmer et al 2015). Of the reported genes, our results were in agreement with that of Bajgain et al (2016) that Gem, Kudu, Paka and Romany all carry the Sr2 gene.…”

“…There is evidence that most APR genes are effective across a number of pathogens, e.g. Sr2/ Yr30/Lr27/Pbc1, Sr55/Lr67/Yr46/Pm46/Ltn3, Sr57/Lr34/Yr18/Pm38/Ltn1 and Sr58/ Lr46/Yr29/Pm39/Ltn2 (William et al 2006;Lillemo et al 2008;Krattinger et al 2009;Mago et al 2011a;Herrera-Foessel et al 2014;Kolmer et al 2015). Several Kenyan cultivars have been shown to be good sources of APR genes controlling stem rust (Knott 1968;Njau et al 2009Njau et al , 2010Onguso and Njau 2015;Bajgain et al 2016).…”

Molecular marker based detection of leaf rust resistance gene Lr34 in Indian bread wheat (Triticum aestivum L.)

“…Earlier, Lr67 was also reported to be either pleiotropic or closely linked with another gene Yr46 (Herrera-Foessel et al 2011) in addition to confirming APR to stem rust and powdery mildew in wheat (Herrera-Foessel et al 2014). Very recently, Lr67 has been cloned (Moore et al 2015).…”

Marker assisted separation of resistance genes Rph22 and Rym16 Hb from an associated yield penalty in a barley: Hordeum bulbosum introgression line

“…With limited sources of new disease resistance genes, there is a need to develop more durable solutions. Partial, quantitative or adult plant resistance (APR) genes fall into a second category of plant disease resistance that is currently receiving a resurgence of interest especially against the cereal rusts (Case et al 2014;Derevnina et al 2013;Herrera-Foessel et al 2014;Hulbert and Pumphrey 2014;Singh et al 2013a;Ziems et al 2014). For the purposes of this paper, we will use the term partial resistance as inclusive of APR.…”