Development of Wheat-Aegilops caudata Introgression Lines and Their Characterisation Using Genome-Specific KASP Markers

ABSTRACTAegilops caudata L. [syn. Ae. markgrafii (Greuter) Hammer], a diploid wild relative of wheat (2n = 2x = 14, CC), is an important source for new genetic variation for wheat improvement due to a variety of disease resistance factors along with tolerance for various abiotic stresses. Its practical utilisation in wheat improvement can be facilitated through the generation of genome-wide introgressions leading to a variety of different wheat–Ae. caudata recombinant lines. In this study, we report the generation of nine such wheat–Ae. caudata recombinant lines which were characterized using wheat genome-specific KASP (Kompetitive Allele Specific PCR) markers and multi-colour genomic in situ hybridization (mcGISH). Of these, six lines have stable homozygous introgressions from Ae. caudata and will be used for future trait analysis. Through a combination of molecular and cytological analysis of all the recombinant lines, we were able to physically map 182 KASP markers onto the seven Ae. caudata chromosomes, of which 155 were polymorphic specifically with only one wheat subgenome. Comparative analysis of the physical positions of these markers in the Ae. caudata and wheat genomes confirmed that the former had chromosomal rearrangements with respect to wheat, as previously reported. These wheat–Ae. caudata recombinant lines and KASP markers provide a useful genetic resource for wheat improvement with the latter having a wider impact as a tool for detection of introgressions from other Aegilops species into wheat.

Experimental evolutionary studies on the genetic autonomy of the cytoplasmic genome “plasmon” in the Triticum (wheat)–Aegilops complex

The term “plasmon” is used to indicate the whole cytoplasmic genetic system, whereas “genome” refers to the whole nuclear genetic system. Although maternal inheritance of the plasmon is well documented in angiosperms, its genetic autonomy from the coexisting nuclear genome still awaits critical examination. We tested this autonomy in two related studies: One was to determine the persistence of the genetic effect of the plasmon of Aegilops caudata (genome CC) on the phenotype of common wheat, Triticum aestivum strain “Tve” (genome AABBDD), during 63 y (one generation per year) of repeated backcrosses of Ae. caudata and its offspring with pollen of the same Tve wheat, and the second was to reconstruct an Ae. caudata strain from the genome of this strain and its plasmon that had been resident in Tve wheat for 50 generations, and to compare the phenotypic and organellar DNA characteristics between the native and reconstructed strains. Results indicated no change in the effect of Ae. caudata plasmon on Tve wheat during its stay in wheat for more than half a century, and no difference between the native and reconstructed caudata strains in their phenotype and simple sequence repeats in their organellar DNAs, thus demonstrating the prolonged genetic autonomy of the plasmon from the coexisting genomes of wheat and several other species that were used in the reconstruction of Ae. caudata. The relationship between the proven genetic autonomy of the plasmon under changing nuclear conditions and its diversification during evolution of the Triticum–Aegilops complex is discussed.