Conversion of an amplified fragment length polymorphism marker into a co-dominant marker in the mapping of the Rph15 gene conferring resistance to barley leaf rust, Puccinia hordei Otth.

Abstract

Leaf rust, caused by Puccinia hordei, is an important disease afflicting barley ( Hordeum vulgare) in many production regions of the world. The leaf rust resistance gene Rph15 was identified in an accession of wild barley ( Hordeum vulgare subsp. spontaneum) and is one of the most broadly effective resistance genes known. Using amplified fragment length polymorphism (AFLP) and simple sequence repeat markers, Rph15 was mapped to chromosome 2HS in an F(2) population derived from a cross between Bowman ( Rph15), a Bowman backcross-derived line carrying Rph15, and the susceptible cultivar Bowman. AFLP marker P13M40 co-segregated with Rph15 in this mapping population and two others involving Bowman ( Rph15) and cultivars Proctor and Nudinka. The dominant AFLP marker P13M40 was converted to a co-dominant PCR-based marker that may be useful in breeding programs employing marker-assisted selection. The allelic relationship between Rph15 and the gene Rph16, also mapping to chromosome 2HS, was studied. The lack of segregation in F(2) progeny derived from the two resistance sources indicates that Rph15 and Rph16 are alleles of the same locus.

Variation in partial resistance to barley leaf rust (Puccinia hordei) and agronomic characters of Ethiopian landrace lines

“…Evaluation of the Hordeum gene pool (H. vulgare, its wild progenitor H. spontaneum, and H. bulbosum) have resulted in the identification of 19 major race-specific resistance genes, Rph1 to Rph19 (Weerasena et al 2003). However, cultivars with this type of resistance are not durable because of the frequent breakdown of resistance by new virulent pathotypes of the pathogen and they are nearly exhausted.…”

Host and Nonhost Response to Attack by Fungal Pathogens

“…However, durable, monogenic resistances acting in a race-specific manner against fungi do exist implying that a priori pessimism with regard to the usefulness of racespecific R-genes may not be appropriate. Typical examples of major R-genes usually exhibiting a high degree of fungal race specificity are the Ml genes including the Mla1-Mla32 allelic series for resistance to Bgh (Jorgensen 1994), Rph1-Rph19 for resistance to P. hordei (Weerasena et al 2004) or Rrs1-Rrs15 for resistance to R. commune (Wagner et al 2008). In some interactions such as the one with F. graminearum or B. sorokiniana, no or very few R-genes mediating qualitative and race-specific resistance have been identified until present but instead, small-to major-effect QTL were found (Kumar et al 2002;Bai and Shaner 2004).…”

Marker assisted selection in crop plants

“…Broadly effective Weerasena et al (2004) For pathogens that can easily generate new virulent pathotypes, such as rusts and mildews, high and durable levels of resistance should be achievable by MAS. Of almost 50 known Lr resistance genes against the damaging leaf rust disease of wheat, the slow rusting genes Lr34 and Lr46 have been effective over a long period of time, in different environments and against different pathotypes of the fungus (Kolmer, 1996;Singh et al, 1998).…”