David Moody and Livinus Emebiri
Our focus in this project is to increase genetic diversity by exploiting natural genetic variation in synthetic hexaploid wheats (SHW) to improve productivity in Australia. Our approach is to import, multiply, characterise and evaluate SHW for abiotic and biotic stresses and introgress novel genetic diversity for stress tolerance into adapted cultivars.
Some of the progress made in wheat breeding and variety development has been through the use of wild relatives of wheat to overcome major biotic and abiotic stresses including quality, and adaptation to different growing conditions. Bread wheat (Triticum aestivum, AABBDD, 2n=42) has no wild form since it arose by chance outcrossing of a cultivated tetraploid and diploid progenitor species over 10,000 years ago. As such, there is limited genetic variation in cultivated wheat since only a very narrow range of the genetic variation then present in its progenitor species across its wide ecological range was incorporated in hexaploid wheat. The wide ecogeographical range of the progenitor species, in particular Ae. tauschii, prompted substantial efforts by wheat geneticists towards their conservation through collections from their regions of natural distribution (Kihara et al. (1965), Halloran (1968), Yen et al. (1983) and Jaaska (1995)), possibly on the assumption that the broad geographical distribution contains substantial genetic variation that potentially reflects adaptation to specific traits.
The exploitation of the wild relatives has occurred mostly through synthetic hexaploid wheat (SHW) 'recreated' from artificial hybridisation between its progenitor species, Aegilops tauschii (syn Ae. squarrosa, Triticum tauschii) and Triticum turgidum ssp. durum). CIMMYT, through Dr Mujeeb Kazi, has produced 1014 SHW. A total of 422 CIMMYT SHW have been imported into Australia, 252 from 2001-2005 through Richard Trethowan and 170 from 1996-1998 by DPI Vic-Horsham. It is thus desirable that all non-overlapping SHW available in CIMMYT be imported, along with their durum and Ae. tauschii parents.
Our preliminary evaluation for a range of abiotic and biotic stresses, and results from previous studies, indicate that some SHW possess tolerance to biotic and abiotic stresses (Ogbonnaya et al 2003, 2004, Dreccer et al. 2003, 2004).
Substantially broaden the original number of SHWs that have been imported for evaluation in Australia between 2001 to 2004 by importing non-overlapping SHW curently available in CIMMYT, Mexico: specifically, an additional 562 of the 1014 SHW that were produced up to the end of 2004 including the the corresponding Triticum turgidum ssp. durum and Aegilops tauschii parents.
Multiply, distribute and evaluate 100 accessions each year for boron, salinity and aluminium tolerance, cereal cyst nematode, root lesion nematode,Septoria nodorum blotch, Septoria tritici blotch, crown rot, leaf, stem and stripe rusts, seed dormancy, HMW & LMW glutenins, LMA, other quality traits using NIR such protein, milling yield, colour and rheological properties.
The 100 SHW will comprise 50 SHW sent from CIMMYT by Dr Richard Trethowan in 2005 and 50 SHW that have been previously evaluated. Because of the quantitative nature of the complex traits with huge GxE interactions, it is important to re-screen potentially resistant lines at least once.
Genetic characterisation will include use of markers for aluminium tolerance gene ALMT1, CCN genes Cre1 and Cre3, Purindoline genes PinA and PinBb, glutenin alleles GluB3, GluD1d, GluA3 and Glu1Bx7, rust markers Lr34 and Sr2, vernalisation and photoperiod genes, preharvest sprouting QTLs and boron tolerance QTLs.
Cross the most promising SHW, which carry multiple biotic and abiotic stresses, with adapted wheat cultivars representative of the Australian agro-ecological zones, to fast-track the development of elite breeder-friendly parental stocks.
Develop strategies for efficient introgression of novel alleles from SHW into elite Australian wheat varieties.
Evaluate the genetic diversity in SHW for novel genes using both functional and linked markers.
Produce additional synthetic wheats from a core set of agronomically outstanding and genetically diverse T. dicoccum (AABB), T. dicoccoides(AABB) and Ae. tauschii (DD). This will allow genetic diversity from wheat's wild relatives, beyond that of just the D-genome (Ae. tauschii), to be explored and used within Australia.
Develop SYNMAP (a graphical genome representation of synthetic diversity based on functional and genome specific SSRs) of the SHW genome, derived from patterns of genetic variation in unrelated individual SHW from distinct parentage.
Link data in SYNDATA (the DPI Vic database management system for the storage and retrieval of data on synthetics and synthetic derived lines) to the CAGE site, to facilitate on-line access to all information derived from the results of the evaluation and enhance the use of SHW in wheat research and cultivar development in Australia.
We intend to collaborate with Julie Nicol - CIMMYT, Turkey on the International Root Disease Resistant Nursery. This will enhance the screening of SBLs with more pathotypes and enhance the discovery of SBLs with potential to provide resistance to a broad range of disease pathotypes.
The first Synthetics Wheat Symposium, including Australian wheat breeders and geneticists, and featuring several leading international scientists, was held in September 2006 at the DPI Grains Innovation Park, Horsham, Vic.
Identification of new sources of resistance to abiotic and biotic stresses.
Synthetic backcross-derived lines (SBLs) /segregating populations with multiple stress tolerance.
New synthetics based on novel alleles from AB (dicoccum and dicoccoides) and D progenitor species of wheat.
See also the Access database, elite selections 2006.xls and SYNDATA summary.xls which may be downloaded from the SynERGE (Synthetic Enriched Resources for Genetic Evaluation) page on the DPI Vic. website