Identification and Molecular Characterization of Leaf Rust Resistance Gene Lr14a in Durum Wheat

Abstract

Leaf rust, caused by Puccinia triticina, is an important disease of durum wheat (Triticum turgidum subsp. durum) and only a few designated resistance genes are known to occur in this crop. A dominant leaf rust resistance gene in the Chilean durum cv. Llareta INIA was mapped to chromosome arm 7BL through bulked segregant analysis using the amplified fragment length polymorphism (AFLP) technique, and by mapping three polymorphic markers in the common wheat (T. aestivum) International Triticeae Mapping Initiative population. Several simple sequence repeat (SSR) markers, including Xgwm344-7B and Xgwm146-7B, were associated with the leaf rust resistance gene. Resistance response and chromosomal position indicated that this gene is likely to be Lr14a. The SSR markers Xgwm344-7B and Xgwm146-7B and one AFLP marker also differentiated common wheat cv. Thatcher from the near-isogenic line with Lr14a, as well as durum ‘Altar C84’ from durum wheat with Lr14a. This is the first report of the presence of Lr14a in durum wheat, although the gene originally was transferred from emmer wheat ‘Yaroslav’ to common wheat. Lr14a is also present in CIMMYT-derived durum ‘Somateria’ and effective against Mexican and other P. triticina races of durum origin. Lr14a should be deployed in combination with other effective leaf rust resistance genes to prolong its effectiveness in durum wheat.

Short communication: Emergence of a new race of leaf rust with combined virulence to Lr14a and Lr72 genes on durum wheat

“…SSR markers Xgwm344 and Xgwm146 were used to detect the presence of the Lr14a gene. These markers are dominant and linked in coupling with that gene (Herrera-Foessel et al, 2008).…”

“…This information is important to guide breeders in their breeding programmes and gene deployment strategies. For more than three decades, the leaf rust resistance gene Lr14a has been effective in protecting durum wheat against leaf rust in Spain The presence of this commonly occurring gene in durum wheat germplasm was first reported by Herrera-Foessel et al (2008), who also found two closely linked SSR (Single Se-2 var 'Altar C84', released in Spain as 'Gallareta'. This gene effectively protected the majority of durum wheat cultivars against the Mexican leaf rust races for nearly two decades, but the resistance it provided was overcome by the race BBG/BN in 2001 in Mexico, and later in other parts of the world (Singh et al, 2004).…”

Diagnostic value of molecular markers for Lr genes and characterization of leaf rust resistance of German winter wheat cultivars with regard to the stability of vertical resistance

“…'Thatcher' and also significant differences between years were observed (indicated by asterisks in Table 5). Lr13 remained at a lower infection level in relation to 'Thatcher' from 2002(p<0.041) except in 2005, 2008 NILs that carry Lr13 turned out to be as susceptible as 'Thatcher ' (2007 and 2008, p=0.694; 2009 p=1.000). In these years also, changes in the infection level of Lr14 and Lr37 were observed.…”

Genetic analysis of rust resistance genes in global wheat cultivars: an overview

“…A characteristic feature of durum wheat leaf rust races is virulence to most durum wheat lines and avirulence to most Lr genes present in common wheat lines [77,78]. Thus, the resistance genes that are effective in durum wheat germplasms could be widely ineffective in common wheat lines [79]. In addition, the seedling resistance genes Lr23, Lr10, and Lr33 are not considered effective due to frequent virulence among P. triticina races [78].…”