Mapping of Novel Leaf Rust and Stem Rust Resistance Genes in the Portuguese Durum Wheat Landrace PI 192051

Abstract

Leaf rust caused by Puccinia triticina Erikss. (Pt) and stem rust caused by Puccinia graminis f. sp. tritici Erikss. & E. Henn (Pgt) are serious constraints to production of durum wheat (Triticum turgidum L). The objective of this study was to identify leaf rust resistance (Lr) and stem rust resistance (Sr) genes/QTL in Portuguese durum landrace PI 192051. Four Pt-isolates, representing three virulence phenotypes (BBBQJ, BBBSJ & EEEEE) and six Pgt-races TTKSK, JRCQC, TKTTF, QFCFC, TPMKC and TMLKC were used to evaluate 180 recombinant inbred lines (RILs) derived from the cross Rusty (rust susceptible) × PI 192051-1 (rust resistant) at the seedling stage. The RILs were also phenotyped at the adult-plant stage in a stem rust nursery in Ethiopia in 2017. The RILs were genotyped using the Illumina iSelect 9K wheat SNP array. PI 192051-1 carries a previously unidentified major Sr gene designated as QSr.ace-7A on chromosome arm 7AS and Lr gene Lr.ace-4A in the pericentromeric region of chromosome 4A. In addition, three minor Sr QTL QSr.ace-1A, QSr.ace-2B and QSr.ace-4A were mapped in PI 192051-1 on chromosomes 1AL, 2BL, and 4A, respectively Lr.ace-4A could be co-located or tightly linked to QSr.ace-4A Markers linked to the identified QTL/genes can be used for marker assisted selection. These findings enrich the genetic basis of rust resistance in both durum and common wheat.

Keywords: DGGW; Ethiopia; Puccinia; QTL; SNP; disease resistance; food security; leaf rust; new resistance; wheat.

Figure 1

Distributions of the seedling response data for Puccinia triticina isolates BBBQJ_CA1.2, BBBQJ_Mor38-2, BBBSJ_Tun20-4, and EEEE_Eth50-4 for recombinant inbred lines (RILs) from the cross Rusty × PI 192051-1. Distribution is expressed as the percent individuals within a linearized Stakman scale (0-9). Median phenotypes for PI 192051-1 and Rusty are indicated on the graph.

Figure 2

Distributions of the seedling data to Puccinia graminis f. sp. tritici races QFCFC, TPMKC, TMLKC, JRCQC, TKTTF, and TTKSK and field data in Ethiopia 2017 at two scoring dates (2017-1 and 2017-2) for recombinant inbred lines (RILs) of the cross Rusty × PI 192051-1. Median phenotypes for PI 192051-1 and Rusty are indicated on the graph. X- axes correspond to linearized Stakman scale (0 – 9) for the seedling data and coefficient of infection for the adult plant stage data.

Figure 3

Mapping of leaf rust resistance gene Lr.ace-4A in PI 192051-1 to P. triticina isolates BBBQJ_CA, BBBQJ_Mor, BBBSJ_Tun, and EEEEE_Eth at seedling stage. QTL analysis was performed using composite interval mapping. The QTL analysis LOD threshold is indicated with the blue line. Co-segregating markers were excluded from this map. SNPs and their cosegregating markers are presented in Figure S2.

Figure 4

Mapping of stem rust resistance QTL (QSr.ace-4A and QSr.ace-7A) in the population Rusty × PI 192051-1 at seedling stage to races QFCFC, TPMKC, TMLKC, JRCQC, TKTTF, and TTKSK and at adult plant stage in stem rust nursery in Ethiopia in 2017. All QTL were identified using composite interval mapping. The QTL analysis LOD threshold is shown with the blue horizontal line. Co-segregating markers were excluded from these maps. SNPs and their cosegregating markers are presented in Figure S2.