Novel genetic diversity from synthetic wheats in breeding cultivars for changing production conditions Maarten van Ginkel * , Francis Ogbonnaya Victorian Department of Primary Industries, Private Bag 260, Horsham, Victoria 3401, Australia Received 14 September 2006; received in revised form 7 November 2006; accepted 23 February 2007 Abstract 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. Crown Copyright # 2007 Published by Elsevier B.V. All rights reserved. Keywords: Hexaploid wheat; Triticum species; Genetic diversity; Adaptation to drought; Salinity; Abiotic stresses; Biotic stresses 1. Introduction In 2005, 220 million ha of wheat were grown around the world, producing 630 million tonnes of grain. Wheat is planted from just above the northern polar circle in Scandinavia (658N) to the equatorial regions of east and central Africa, and from elevations up to 3000 m above sea level in the Andean region of Latin America to reclaimed polders several meters below sea level in the Netherlands. It is estimated that more than 75% of the world’s population consumes wheat as part of its diet daily, with annual consumption per person in the newly independent republics in the Caucuses region and parts of northern Africa reaching 200 kg (Pingali, 1999). Since the mid-1970s most of the expanded adoption of new varieties has taken place in rainfed areas, rather than irrigated regions (Reynolds and Borlaug, 2006). In many rainfed environments annual production per ha increased a surprising 1–3% (Trethowan et al., 2002), in part as a result of the adoption of improved management practices including minimum or zero-tillage. While both genetic and agronomic progress in increasing yield and adaptation have been very successful, studies on synergistic interactions between modern varieties and modern production methods remain rare (Trethowan et al., 2005) with other opportunities for improvement lost. A new generation of wheat varieties generated using synthetic wheats produced by intercrosses between synthetic derivatives and common wheat is on the horizon and agronomists and breeders should work closely together to enable these new genetic resources to translate optimally into more stable, increased production and return for growers. 2. Origins of wheat 2.1. Wheat’s parents Early wild wheat was domesticated by humans who were beginning to adopt sedentary agriculture about 10,000 years ago in the Fertile Crescent region in western Asia (Feldman, 2001). The wheat plants selected for domestication were the www.elsevier.com/locate/fcr Field Crops Research 104 (2007) 86–94 * Corresponding author. Tel.: +61 3 5362 0789; fax: +61 3 5362 2187. E-mail address: maarten.vanginkel@dpi.vic.gov.au (M. van Ginkel). 0378-4290/$ – see front matter. Crown Copyright # 2007 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.fcr.2007.02.005