Gametocidal genes of Aegilops: segregation distorters in wheat-Aegilops wide hybridization

Aegilops is a genus belonging to the family Poaceace, which have played an indispensible role in the evolution of bread wheat and continues to do so by transferring genes by wide hybridization. Being the secondary gene pool of wheat, gene transfer from Aegilops poses difficulties and segregation distortion is common. Gametocidal genes are the most well characterized class of segregation distorters reported in interspecific crosses of wheat with Aegilops. These "selfish" genetic elements ensure their preferential transmission to progeny at the cost of gametes lacking them without providing any phenotypic benefits to the plant, thereby causing a proportional reduction in fertility. Gametocidal genes (Gc) have been reported in different species of Aegilops belonging to the sections Aegilops (Ae. geniculata and Ae. triuncialis), Cylindropyrum (Ae. caudata and Ae. cylindrica), and Sitopsis (Ae. longissima, Ae. sharonensis, and Ae. speltoides). Gametocidal activity is mostly confined to 2, 3, and 4 homeologous groups of C, S, S¹, S^sh, and M^g genomes. Removal of such genes is necessary for successful alien gene introgression and can be achieved by mutagenesis or allosyndetic pairing. However, there are some instances where Gc genes are constructively utilized for development of deletion stocks in wheat, improving genetic variability and chromosome engineering.