Triple whammy - breeding wheat for increased winter growth rate.

Crop root growth has generated significant interest with regard to net zero agriculture, because increasing root mass captures more carbon in the soil, and leads to more effective uptake of nitrogenous fertilizer. A larger and deeper root system also improves drought resilience, an increasing requirement even in the UK. However, there has been a progressive reduction in wheat root mass in elite lines over the last 40-years, likely as result of breeding under conditions on high fertilization, and breeding for increased harvest index.

Our recent results suggest that reduction in wheat root mass has also contributed to increasingly problematic yield losses to blackgrass weed infestations. We thus hypothesise that by breeding for wheat with faster winter growth, especially in the root system, we can achieve a 'triple whammy' - increasing carbon capture and nutrient uptake, increasing drought resilience, and increasing resistant to blackgrass.

While such a strategy might not have been possible in harder winters of the past, the rapidly warming winters provide an opportunity to increase crop growth during this period when wheat has traditionally been dormant.

Examining winter growth rate as a mechanism to improve root growth (and plant vigour in general) represents a novel approach to improving the agronomic properties of wheat. There is a pressing need to adapt our agricultural systems for the transition to net zero, and this project will contribute to our ability to do that by enhancing agronomic properties of wheat.

Objectives: The aim of this project is therefore to improve our understanding of winter growth in wheat. Specific objectives are: 1. To screen for wheat germplasm with enhanced winter growth 2. To genetically map winter growth loci 3. To test the effect of faster winter growth under field conditions.

Experimental approach:

First, a hydroponic system will be used to screen ~120 diverse wheat varieties from KWS/RAGT/Limagrain breeding programs, in order to determine relative rates of shoot and root growth during simulated winter. Careful phenotypic analyses will be used to understand how differences in growth rate arise between lines, and whether there are knock-on consequences of this elsewhere in development.

Then, data from objective 1 will be used to identify two 'extreme' varieties with either very high or low winter growth rate. Using mapping populations developed by the industrial partners, the F2 progeny will be phenotyped for differences in winter growth, and QTL analyses will be performed to identify loci that control winter growth rate. Candidate genes from these loci will then be assessed to identify those which function in the regulation of winter growth rate.

Field trials using the lines identified in objective 1 will be performed in coordination with the industrial partners at multiple sites, in order to test the functional relevance of the high/low winter growth rates under different environmental conditions.