Selecting winter wheat lines from a composite cross population

Summary

The extremely diverse genetic variation in wheat Composite Cross Populations (CCP) represents a valuable source of breeding material. Such material could be selected as part of a participatory breeding programme with the potential advantage of selecting adaptation targeted for particular environments. For example, selections could be made aimed at producing lines that would thrive under the wide range of management practices conducted as part of organic and low input farming systems.
Ears were selected from a CCP mixed stand under organic field conditions in the UK and Hungary. Selected lines were multiplied as single ear rows and 1m2 plots. The best performing five lines from the two selection sites were trialled in Suffolk, UK, in replicated plots including a commercial control variety (Alchemy) and the original population. Alchemy was chosen due to its good disease resistance and consistent performance at the trial site. Assessments included crop and weed cover, foliar and ear diseases, Leaf Area Index (LAI), crop height, as well as grain and straw yield. The first year of trials has been completed with five of the Hungarian selected lines and trials including locally selected lines are on-going.
For the first trial year including only the Hungarian selected lines, there were significant differences among varieties (P<0.001) and Alchemy had the highest average yield. Across all trial entries grain yield was correlated negatively with yellow rust infection on the flag leaf at heading (P<0.001) and with reduced green leaf area during grain ripening (P<0.001). In current trials including locally selected lines, some of the selected lines had significantly lower yellow rust infection than the average of the original CCP and of the control variety Alchemy (P<0.001). There was also greater early ground cover (P<0.005) and (LAI) at tillering (P<0.05) in some lines compared to Alchemy and the original population. Crop cover was also correlated negatively with early weed cover (P<0.05). These observations suggest that it is possible to select lines with enhanced resistance to local disease and the ability to compete with weeds at an early stage. However, because average grain yields and percentage protein content are negatively correlated in this study (P<0.01), this trade-off should not be ignored when selecting lines for specific end uses. This can be avoided by developing mixtures of high performing lines with potentially greater stability than pure-line monocultures. Such mixtures may perform better than the original CCP but with the risk of reduced stability over multiple seasons because of their reduced diversity.
Acknowledgements: The work reported here is supported by the EU Core Organic II project COBRA.