Abstract
Leaf rust, caused by Puccinia triticina, and stem rust, caused by P. graminis f. sp. tritici, are important diseases of durum wheat. This study determined the inheritance and genomic locations of leaf rust resistance (Lr) genes to P. triticina race BBBQJ and stem rust resistance (Sr) genes to P. graminis f. sp. tritici race TTKSK in durum accessions. Eight leaf-rust-resistant genotypes were used to develop biparental populations. Accessions PI 192051 and PI 534304 were also resistant to P. graminis f. sp. tritici race TTKSK. The resulting progenies were phenotyped for leaf rust and stem rust response at seedling stage. The Lr and Sr genes were mapped in five populations using single-nucleotide polymorphisms and bulked segregant analysis. Five leaf-rust-resistant genotypes carried single domi-nant Lr genes whereas, in the remaining accessions, there was deviation from the expected segregation ratio of a single dominant Lr gene. Seven genotypes carried Lr genes different from those previously characterized in durum. The single dominant Lr genes in PI 209274, PI 244061, PI387263, and PI 313096 were mapped to chromosome arms 6BS, 2BS, 6BL, and 6BS, respectively. The Sr gene in PI 534304 mapped to 6AL and is most likely Sr13, while the Sr gene in PI 192051 could be uncharacterized in durum.
Highlights
P. graminis f. sp. tritici race TTKSK in durum accessions
The number of genes conferring resistance against P. triticina race BBBQJ in the eight durum wheat genotypes was determined by evaluating the infection types (IT) at seedling stage of F1 plants and the segregation ratios of F2, F3, and F6 progenies (Table 2)
The F1 plants of the cross Divide × plant introduction (PI) 278379 were susceptible to BBBQJ, indicating that the resistance was recessive (Table 2)
Summary
P. graminis f. sp. tritici race TTKSK in durum accessions. Eight leaf-rustresistant genotypes were used to develop biparental populations. Five leaf-rust-resistant genotypes carried single dominant Lr genes whereas, in the remaining accessions, there was deviation from the expected segregation ratio of a single dominant Lr gene. Durum wheat has been traditionally considered more resistant to leaf rust (caused by Puccinia triticina Erikss.) than common wheat (T. aestivum L.; 2n = 6x = 42). In recent years, P. triticina races highly virulent on resistant durum wheat cultivars are increasingly affecting durum production worldwide (Goyeau et al 2006; Huerta-Espino et al 2009; Singh et al 2004). P. triticina race BBG/BN and its variants, with virulence to leaf rust resistance (Lr) gene Lr72, overcame the resistance of the adapted
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