Novel genetic diversity from synthetic wheats in breeding cultivars for changing production conditions

Bread wheat, the most widely cultivated and consumed food crop, developed in two stages through natural intercrossing among diploid grass species. About 10,000 years ago the cross between Aegilops speltoides and Triticum urartu resulted in T. dicoccoides (wild emmer). In about 6000 bc the domesticated version of this latter species, T. dicoccum (cultivated emmer) intercrossed naturally with Aegilops tauschii (goat grass). This cross resulted in T. aestivum (modern hexaploid bread wheat), while T. dicoccum itself evolved into T.turgidum ssp. durum (modern tetraploid durum wheat). Bread wheat can be artificially recreated by intercrossing modern tetraploid durum wheat with present-day derivatives of goat grass, with synthetic hexaploids developed in the USA, Mexico and at the Department of Primary Industries, Victoria, Australia now available in large numbers. A number of these hexaploids have shown resistance to major wheat diseases and tolerance to abiotic stresses such as drought, heat, waterlogging, salinity and pre-harvest sprouting. High end-use quality derivatives that meet industry standards have also been developed, while recent experiments have identified synthetic wheat derivatives that outyield commercial varieties under rainfed conditions by 18–30%. At the molecular level these new synthetic derivatives have been shown to boost genetic diversity.