Marker Assisted Transfer of Stripe Rust and Stem Rust Resistance Genes into Four Wheat Cultivars

Three rust diseases namely; stem rust caused by <i>Puccinia</i> <i>graminis</i> f. sp. <i>tritici</i> (Pgt), leaf rust caused by <i>Puccinia</i> <i>triticina</i> (Pt), and stripe rust caused by <i>Puccinia</i> <i>striiformis</i> f. sp. <i>tritici</i> (Pst), are the most common fungal diseases of wheat (<i>Triticum</i> <i>aestivum</i> L.) and cause significant yield losses worldwide including Australia. Recently characterized stripe rust resistance genes <i>Yr51</i> and <i>Yr57</i> are effective against pre- and post-2002 Pst pathotypes in Australia. Similarly, stem rust resistance genes <i>Sr22, Sr26,</i> and <i>Sr50</i> are effective against the Pgt pathotype TTKSK (Ug99) and its derivatives in addition to commercially important Australian pathotypes. Effectiveness of these genes make them good candidates for combining with known pleiotropic adult plant resistance (PAPR) genes to achieve durable resistance against three rust pathogens. This study was planned to transfer rust resistance genes <i>Yr51, Yr57, Sr22, Sr26,</i> and <i>Sr50</i> into two Australian (Gladius and Livingston) and two Indian (PBW550 and DBW17) wheat cultivars through marker assisted selection (MAS). These cultivars also carry other rust resistance genes: Gladius carries <i>Lr37</i>/<i>Yr17</i>/<i>Sr38</i> and <i>Sr24</i>/<i>Lr24</i>; Livingston carries <i>Lr34</i>/<i>Yr18</i>/<i>Sr57</i>, <i>Lr37</i>/<i>Yr17</i>/<i>Sr38,</i> and <i>Sr2</i>; PBW550 and DBW17 carry <i>Lr34</i>/<i>Yr18</i>/<i>Sr57</i> and <i>Lr26</i>/<i>Yr9</i>/<i>Sr31</i>. Donor sources of <i>Yr51</i> (AUS91456), <i>Yr57</i> (AUS91463), <i>Sr22</i> (<i>Sr22</i>/3*K441), <i>Sr26</i> (<i>Sr26</i> WA1), and <i>Sr50</i> (Dra-1/Chinese Spring ph1b/2/3* Gabo) were crossed with each of the recurrent parents to produce backcross progenies. Markers linked to <i>Yr51</i> (<i>sun104</i>), <i>Yr57</i> (<i>gwm389</i> and <i>BS00062676</i>), <i>Sr22</i> (<i>cssu22</i>), <i>Sr26</i> (<i>Sr26#43</i>)<i>,</i> and <i>Sr50</i> (<i>Sr50</i>-<i>5p-F3, R2</i>) were used for their MAS and markers <i>csLV34</i> (<i>Lr34</i>/<i>Yr18</i>/<i>Sr57</i>)<i>,</i> VENTRIUP-LN2 (<i>Lr37</i>/<i>Yr17</i>/<i>Sr38</i>), <i>Sr24#12</i> (<i>Sr24</i>/<i>Lr24</i>), and <i>csSr2</i> (<i>Sr2</i>) were used to select genes present in recurrent parents. Progenies of selected individuals were grown and selected under field conditions for plant type and adult plant rust responses. Final selections were genotyped with the relevant markers. Backcross derivatives of these genes were distributed to breeding companies for use as resistance donors.