TY  - PRO
AU  - Krattinger,S.G.
AU  - Lagudah,E.S.
AU  - Spielmeyer,W.
AU  - Singh,R.P.
AU  - Huerta-Espino,J.
AU  - McFadden,H.
AU  - Bossolini,E.
AU  - Selter,L.L.
AU  - Keller,B.
TI  - Molecular basis of durable rust resistance in wheat
PY  - 2009///
CY  - Antalya (Turkey)
PB  - METU
KW  - AGROVOC
KW  - Rusts
KW  - Disease resistance
KW  - Wheat
KW  - Food security
N1  - Abstract only
N2  - Improved resistance to fungal rust diseases in cereals is critical for world food security and can only be achieved through breeding varieties with durable rust resistance. Durable resistance is not caused by single genes, but by a combination of usually 3-5 individual partial genes which are combined by classical breeding in a single wheat line to achieve near immunity. The wheat gene Lr34 is such a quantitatively acting, partial resistance gene which is involved in durable resistance. Lr34 is associated with resistance to two different rust diseases of wheat, leaf rust (caused by Puccinia triticina) and stripe rust (P. striiformis). Interestingly, it also confers partial resistance to the powdery mildew pathogen. Lr34 is expressed in adult plants during the critical grain filling stage and is most effective in the flag leaf. Flag leaves of many wheat cultivars containing Lr34 develop a necrotic leaf tip, a morphological marker described as leaf tip necrosis. The expression of this trait, however, is strongly dependent on the environment. The Lr34 gene was first documented in Canada although Lr34-containing germplasm has been a part of wheat improvement since the early part of the 20th century and seems to have originated in Italian and Chinese material. Wheat cultivars containing Lr34 occupy more than 26 million hectares in various developing countries alone and contribute substantially to yield savings in epidemic years.|The Lr34 gene has remained durable and no evolution of increased virulence towards Lr34 has been observed for more than 50 years of large scale use in resistant wheat lines. Despite the importance of partially acting plant resistance genes involved in durable resistance, very little is known on them at the molecular level. Understanding the molecular nature of this class of resistance has important implications for long term control of rust diseases. Previous studies have localized the co-dominant gene Lr34 on the short arm of wheat chromosome 7D between the two markers gwm1220 and SWM10. We further reduced the target interval in a map-based cloning approach based on three high-resolution populations. High-resolution mapping revealed a 0.15 cM target interval for Lr34. The 363 kb physical interval containing both flanking markers was fully sequenced in the Lr34 containing hexaploid wheat cultivar ?Chinese Spring?. A PDR/ABC transporter coding gene was finally identified as Lr34 by the molecular analysis of 8 independent mutants. The mutations were identified as missense mutations, splice site mutations and short deletions. Interestingly, an allele of the Lr34 gene is also found in all wheat lines lacking Lr34 activity. This susceptible allele differed from the resistant form in only two amino acid changes. Based on these polymorphisms, highly specific molecular markers have recently been developed. They allow diagnostic detection of Lr34 in tested germplasm and will be highly useful in combining Lr34 with other partial resistance genes to achieve near immunity. Recent data on Lr34 orthologs in several Triticeae and other grass genomes will be presented. In addition, strategies for molecular understanding of LR34 function and possible applications in agriculture will be discussed
T2  - International Cereal Rusts Powdery Mildews Conference : Antalya (Turkey); 13-16 Oct 2009, Abstract Book
ER  -