Mining of Leaf Rust Resistance Genes Content in Egyptian Bread Wheat Collection

Abstract

Wheat is a major nutritional cereal crop that has economic and strategic value worldwide. The sustainability of this extraordinary crop is facing critical challenges globally, particularly leaf rust disease, which causes endless problems for wheat farmers and countries and negatively affects humanity's food security. Developing effective marker-assisted selection programs for leaf rust resistance in wheat mainly depends on the availability of deep mining of resistance genes within the germplasm collections. This is the first study that evaluated the leaf rust resistance of 50 Egyptian wheat varieties at the adult plant stage for two successive seasons and identified the absence/presence of 28 leaf rust resistance (<i>Lr</i>) genes within the studied wheat collection. The field evaluation results indicated that most of these varieties demonstrated high to moderate leaf rust resistance levels except Gemmeiza 1, Gemmeiza 9, Giza162, Giza 163, Giza 164, Giza 165, Sids 1, Sids 2, Sids 3, Sakha 62, Sakha 69, Sohag 3 and Bany Swif 4, which showed fast rusting behavior. On the other hand, out of these 28 <i>Lr</i> genes tested against the wheat collection, 21 <i>Lr</i> genes were successfully identified. Out of 15 <i>Lr</i> genes reported conferring the adult plant resistant or slow rusting behavior in wheat, only five genes (<i>Lr13</i>, <i>Lr22a</i>, <i>Lr34</i>, <i>Lr37</i>, and <i>Lr67)</i> were detected within the Egyptian collection. Remarkedly, the genes <i>Lr13</i>, <i>Lr19</i>, <i>Lr20</i>, <i>Lr22a</i>, <i>Lr28</i>, <i>Lr29</i>, <i>Lr32</i>, <i>Lr34</i>, <i>Lr36</i>, <i>Lr47</i>, and <i>Lr60</i>, were found to be the most predominant <i>Lr</i> genes across the 50 Egyptian wheat varieties. The molecular phylogeny results also inferred the same classification of field evaluation, through grouping genotypes characterized by high to moderate leaf rust resistance in one cluster while being highly susceptible in a separate cluster, with few exceptions.