Chengdao Li

Barley(Hordeum vulgare L.) is one the most important cereal crops in the world and cultivated both in highly productive agricultural regions as well as in marginal environments prone to adverse conditions.As a particularly resilient crop compared to other cereals such as wheat and rice,barley has the ability to adapt to biotic and abiotic stresses,holding much potential to increase production in marginal areas to sustain food security.Barley genome sequences from over 20 accessions are close to be completed at the reference genome levels by the end of this year,which include wild barley,landraces and cultivated barley.The genome sequences will provide unprecedent resources for genomics breeding Seventy percent more food needs to be produced to meet the global human population projected to grow into nine billion by 2050.Efforts of achieving this substantial increase have been retarded by the adverse impact of projected climate change on crop yield.Modelling studies on crop growth and climate change have produced robust estimates of the potential impact on global crop production under different emission scenarios.However,uncertainty in future CO_2 emission magnifies the uncertainties in modelling the impact of future climate change on global crop production.Furthermore,previous studies on predicting the impact of climate change on crop yield assume unchanged crop varieties and agronomic practice.We use an example to demonstrate how genomics selection can be used to improve barley yield under climate change

The identification and deployment of disease resistance genes are key objectives of Australian barley breeding programs. A doubled haploid (DH) population derived from the cross VB9104 × Dash was used to identify markers for resistance to scald (Rhynchosporium secalis). The map comprised of 205 markers including SSRs and AFLPs. The population was assessed for severity of scald during grain fill in a field trial in South Australia. Marker analysis was performed using the software packages Mapmanager and Qgene. QTL analysis identified a region on chromosome 3H, associated with scald resistance in a number of studies, and a region on 4H which has not previously been associated with scald resistance. R2 values for the 3H and 4H chromosome regions were 29% and 22%, respectively. Multiple regression analysis of these two QTLs explained 42% of the variation. There are a number of markers showing strong associations with the resistance in these regions. These markers present an opportunity for marker assisted selection of lines with resistance to scald in barley breeding programs.

An extensive collection of barley maps has allowed us to compile a consensus map of barley. The consensus map was informed using four barley maps produced in our laboratory as well as a number of other Australian and international published genetic maps and includes over 2000 markers. CMap software was used to view the consensus map and validate marker order by comparison of the consensus map to the individual maps that contributed to the consensus map. The options in CMap such as the matrix were found useful for quickly assessing the occurrence of duplicate loci. The alignment of different genetic maps was generally unambiguous with respect to the order of loci and examples of alignments will be presented together with an estimate of the error inherent in producing the consensus map. QTLs were also inserted into map in a searchable format within the software and this has enhanced the value of the map considerably.

The technologies of Marker-assisted selection (MAS), Doubled Haploid (DH), and Single Seed Descent (SSD) are now providing the basis for significant advances in the way wheat and barley breeding is carried out. In the barley breeding program in WA, for example, DH lines represent over 25% of the overall breeding program and 45% of the stage 2 or pure breeding component with the proportion of DH lines set to increase in the future. Since 1993, over 25,000 barley DH lines have been produced in WA. In addition 4,000 lines each year are produced from the SSD program. Doubled haploids and single seed descent reduce the time taken to release a variety by 2 to 3 years. However, large numbers of DH lines and SSD lines tested in the field and derived from the F1 of single crosses have limited genetic value. Marker assisted selection applied to segregating populations backcrossed, top-crossed or F2, both pre- and post DH production, and pre-single seed descent will enhance the genetic value of populations through the selection for desirable traits. In this view of the wheat and barley breeding programs, it is evident that major gaps exist in the suite of marker-trait combinations, as well as low cost/high throughput technologies for background selection (eg DArTs), that are available for application in the breeding program. Investigation of the DArT-type analysis in collaboration with the CAMBIA group indicated that the technology may have a role to play in the analysis of barley breeding lines. The status of new marker-trait combinations that are available for implementing the strategies discussed will be presented.

Net type net blotch caused by Pyrenophora teres f. teres is a major disease in Western Australia which reduces significant barley production around the world. Studies were focussed on four resistant lines to identify microsatellites linked with the resistance. The four lines, WA 4794 (103 IBON 91) (Pedigree: Arupo S × 2/3/PI 2325/Maf 102//Cossack), Pompadour (Pedigree: FDO192/Patty), CI 9214 (Pedigree: Collected from South Korea) and WPG 8412-9-2-1 (Pedigree: Bowman//Ellice/TR451) were crossed with Stirling (Pedigree: Dampier//Prior/Ymer/3/Piroline), a susceptible but well adapted cultivar in Western Australia. Doubled haploid (DH) populations were generated through another culture. In case of WA4794, two genes were mapped on 4H and 6H using the microsatellite markers GMS089, Bmag0384 for 4H, and Ebmac0874 for 6H. In Pompadour population, two NNB resistance genes were mapped on 3H and 6H using the microsatellites Bmac0209 and Bmag0173 respectively. In CI 9214, Bmac0218 was linked with the resistance for 2H, Ebmac0871 with 3H, suite of microsatellites Ebmac0635, Ebmac0701 and Ebmac0788 with 4H, and similarly Bmag0173, Bmgtttttt1, Ebmac0874 and HVM74 with 6H. In case of WPG 8412/Stirling, single gene was mapped on 6H using the microsatellite Bmag0173. The R2 value ranged up to 0.80 for the linked microsatellites and some are closely mapped to the resistance genes.