Description

The Aegilops genus is the closest wild relative of Triticum which includes cultivated forms of wheat. It contains eleven diploid, ten tetraploid and two hexaploid species with six different genomes (D, S, U, C, N and M). Because Aegilops species have never been domesticated they preserved considerable genetic diversity including adaptation to a wide range of ecological conditions, including abiotic stresses (salinity, drought, frost and heat), which are not tolerated by wheat. Similarly, several Aegilops accessions have resistance to fungal pathogens of wheat, including leaf-, stem- and yellow rusts and powdery mildew. The identification of new gene variants related to biotic or abiotic stress resistance should therefore allow the use of these wild gene sources for improving the stress tolerance of wheat. However, neither the mechanisms nor the genes responsible for the abiotic and biotic stress tolerances have been sufficiently studied in Aegilops accessions and work on this topic is urgently required to facilitate their exploitation.

Grains of some Aegilops species have also been reported to contain higher contents of the essential mineral micronutrients Zn and Fe compared to cultivated wheat; suggesting that they can be exploited for the biofortification of wheat. Similarly, significant intraspecific variability exists in the contents of bioactive phytochemicals which may have impacts on human health. Finally, Aegilops species may also be a valuable source of genetic variation in the composition of the gluten storage proteins which determine grain processing quality. In particular, novel variation occurs in the composition of the high molecular wheat subunits of glutenin which are the major determinants of dough elasticity. However, despite these promising studies, the full extent of variation in the composition and properties of Aegilops remains to be determined.

Introgression breeding can be used to increase genetic variation in bread wheat by introducing new genes by interspecific hybridization. Several agronomic traits have already been transferred from Aegilops into wheat by developing wheat-Aegilops hybrids and chromosome addition and translocation lines. These wheat-alien introgression lines are important genetic resources for breeding and are also excellent material to study the performance of alien traits in the wheat genetic background and to assign key genes to alien chromosomes. The development and phenotypic characterisation of wheat-Aegilops introgression lines are therefore important aspects of this Research Topic.

The application of modern genetic and genomic technologies (such as molecular cytogenetic methods, molecular markers, genetic mapping) are valuable tools to follow the introgression of Aegilops genes during the breeding of wheat. The rapidly developing next-generation sequencing technologies also allow the identification of the gene repertoire of individual chromosomes, the comparison of genome structure of wheat and Aegilops and the development of gene-specific markers for high throughput detection of Aegilops chromatin in the wheat genome.

This Research Topic will therefore bring together new knowledge related to resistance to biotic and abiotic stresses and the composition, nutritional quality and processing properties of the grain of Aegilops species. The Topic will also to deliver valuable information on the genome structure of Aegilops and wheat-Aegilops introgression lines at the chromosomal and DNA levels. This knowledge will facilitate the exploitation of genetic potential of Aegilops in wheat improvement.