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RESEARCH ARTICLE
Contents Vol 59(5)

Rebirth of synthetic hexaploids with global implications for wheat improvement

Abdul Mujeeb-Kazi A E , Alvina Gul A , Muhammad Farooq B , Sumaira Rizwan C and Iftikhar Ahmad D
+ Author Affiliations
- Author Affiliations

A National Institute of Biotechnology & Genetic Engineering (NIBGE), Faisalabad, Pakistan.

B Biotechnology Department, University of Karachi, Karachi, Pakistan.

C Department of Biological Sciences, Quaid-e-Azam University, Islamabad, Pakistan.

D National Agricultural Research Center (NARC), Islamabad, Pakistan.

E Corresponding author. Email: m.kazi@cgiar.org

Australian Journal of Agricultural Research 59(5) 391-398 https://doi.org/10.1071/AR07226
Submitted: 14 June 2007  Accepted: 30 October 2007   Published: 12 May 2008

Abstract

Aegilops tauschii (syn.Triticum tauschii (Coss.) Schmalh., syn. Ae. squarrosa auct. Non L., 2n = 2x = 14, DD genome), with its numerous accessions and wide distribution, provides unparallelled genetic diversity for addressing global wheat production constraints through genetic improvement. From our working collection of ~750 Ae. tauschii accessions, hybridisation efforts produced 1014 synthetic hexaploid combinations (2n = 6x = 42, AABBDD), resulting from chromosome doubling of the F1 hybrids between elite Triticum turgidum L. s. lat. cultivars and Ae. tauschii accessions. The extensive production of synthetic hexaploids represents a step-wise progression over 2 decades in the generation of a valuable resource of user-friendly genetic diversity. The synthetic germplasm has been validated, maintained, screened, formed into targetted stress-related subsets for focused utilisation, and been allowed global distribution for use in pre-breeding/breeding with advent into molecular technologies. Abundant synthetic hexaploids with different Ae. tauschii accessions have been identified from their screening for yield per se, and various biotic/abiotic stresses. Encouraging diversity data have been obtained for key abiotic constraints such as drought, salinity, heat, and water-logging. A similar response was prevalent for the salient biotic stresses such as fusarium head scab, spot blotch, septoria leaf blotch, and karnal bunt. Global distribution of the selected synthetics has further added valuable information for several other stress constraints and led to utilisation of the synthetic diversity for molecular investigations. The superiority of the primary synthetics has been transferred with ease via pre-breeding/breeding to conventional bread wheat cultivars and varietal releases have started globally. The success and status of the D genome diversity are the focus of this paper and we are optimistic that researchers will devise additional strategies to harness other genomes as efficiently by adding on new technologies that ensure wheat production security in the decades ahead.

Additional keywords: synthetic hexaploid wheats, interspecific hybridisation, Aegilops tauschii, genetic diversity, biotic stresses, abiotic stresses.


Acknowledgments

The senior author acknowledges CIMMYT where the bulk of the data reported in this paper were generated and are in program files in Mexico with the Wheat Wide Cross program at El-Batan. The germplasm across various stress attributes has been registered in Crop Science, stored in the gene bank in Fort Collins, CO, USA, and in CIMMYT’s gene bank. Following the senior author’s retirement from CIMMYT in October 2004 the synthetic-based germplasm was officially shared and has since been maintained and used in wheat breeding in Pakistan, under the leadership of the senior author. Germplasm details and all registered genetic stocks can be obtained from CIMMYT as well as from A. Mujeeb-Kazi (m.kazi@cgiar.org).


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