Genomic Approaches Towards Durable Fungal Disease Resistance in Wheat

The opinions expressed and arguments employed in this publication are the sole responsibility of the authors and do not necessarily reflect those of the OECD or of the governments of its Member countries.

The Special Session was sponsored by the OECD Co-operative Research Programme on Biological Resource Management for Sustainable Agricultural Systems, whose financial support made it possible for most of the invited speakers to participate in the Special Session.

Abstract In the last years there has been enormous progress in the molecular understanding of fungal disease resistance in plants. Research on effector-based immunity which is mediated by major resistance (R) genes has been greatly stimulated by the molecular isolation of plant resistance genes as well as the first fungal effectors. In addition, the first genes underlying QTLs or partial disease resistance have been cloned. However, much of this work is still in a phase of basic research and there is a need for translational approaches to realize the globally needed improvements of disease resistance in wheat. In particular, it is essential that future strategies are aiming at achieving durable resistance against pathogens. Durable resistance has been defined by Johnson (Genetic background of durable resistance.

In: Lamberti F, Waller JM, Van der Graaff NA (eds) Durable resistance in crops. Plenum, New York, pp 5–24, 1983) as a resistance which remains effective in cultivars that are widely grown for long periods and in environments favorable to the disease. In this article we will discuss different molecular strategies towards achieving durable disease resistance in wheat. In particular, our group focuses on the Pm3 allelic series of race-specific powdery mildew R genes and the Lr34/Yr18/Pm38/ Sr57 race non-specific multi-pathogen resistance gene.

Keywords Allele mining • Allele pyramiding • Durable disease resistance • Fungal pathogens • Multiline approach • Pathogen genomics

Genomics in Wheat: New Tools and Resources

New genomic tools have allowed scientists to develop approaches and strategies which are revolutionizing the way specific questions can be tackled in wheat. The availability of partial or complete genomic sequences, although mostly in a nonordered form, allows for a more efficient characterization of agronomically important genes and to explore their use in classical or transgenic wheat breeding. Map-based isolation of genes relevant for agronomic traits and the study of their allelic diversity have become simpler and faster. In particular, the critical problem of insufficient marker coverage in a targeted region can now be approached more efficiently. In a recent study, we have shown that chromosome sorting performed in the group of J. Dolezel and H. Simkova at the Institute of Experimental Botany in Olomouc, combined with next generation sequencing can be successfully used to efficiently increase the number of single nucleotide polymorphism (SNP) markers in a specific chromosomal region (Shatalina et al. 2013). In this case, the targeted resistance QTL against Stagonospora glume blotch is located on chromosome 3B, the only chromosome that can be isolated in pure form because of its size. However, we have recently found that the same approach can also be used in fractions which are not pure but enriched for a specific chromosome, even if only 25 % of the sample consists of the target chromosome (Singla et al., unpublished data). Although we are only at the beginning of exploiting these new tools, there are already a number of applications which are of direct use and that increase the efficiency of resistance improvement in wheat.

 
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