Phenotyping root function in wheat

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In this project we will develop an application protocol for electromagnetic conductance (EMI) so that it can be used to rapidly measure soil moisture patterns beneath wheat. We will use established methods of electrical resistance tomography (ERT) to "ground-truth" the new EMI protocol. The new method will be tested on and developed with approximately 20 UK wheat lines with known (based on our preliminary data) or perceived differences in rooting, drought tolerance, biomass, etc., selected in conjunction with the wheat breeders. The data from these initial tests will be used to optimise the depth profiling ability of EMI measurements so that they can be used to quantify genotypic differences in water extraction profiles, which we have shown to exist beneath different wheat lines. EMI and ERT data will be compared with data from buried soil moisture meters, soil sampling at various depths, root depth measurement with transparent rhizotrons and the emerging qPCR approach to measuring root DNA concentration in soil. Data from these invasive approaches will be used to validate and refine as necessary the EMI protocol.

We will use the optimised EMI protocol to phenotype root activity of individual lines of the Avalon x Cadenza mapping population for root function QTL discovery. Further phenotypic data will be collected using penetrometer measurements (which are rapid and statistically robust) and other field tests such as root pulling strength. We will adapt the successful maize "shovelomics" approach for wheat, which is based on simple, rapid measurements of excavated root systems.

The project has the potential to make a significant impact on the academic community and the seeds industry. The project will develop a new tool to assess root function via the profile of soil drying beneath contrasting varieties of wheat, although in the longer term the approach we develop can be applied to all crops.

The initial impact on the seeds industry will be to provide a way to identify which wheats are the most effective at extracting water from the deep soil layers. In UK wheat lines Eric Ober has shown that varieties capable of doing this can produce higher yields when water is limited. However, with current methods identification of this trait is laborious and difficult. In the UK approximately 30% of the production of wheat is on soils where insufficient moisture decreases yields by (on average) 1-2 t/ha, costing between £112M and £224M each year in lost production. Thus, the benefit to the UK farming community is considerable and could lead to a more efficient use of water and nutrient resources.

This project has the potential to make international impact because in many parts of the world the yield of wheat is water limited. This is true for developed (e.g. Australia) and developing countries. Further, the approaches we will develop will have generic application, and could be applied to upland rice where the yield is water-limited and the crop is preferentially grown by poorer members of society. Although there have been yield improvements in rice and other crops by conventional selection for yield, greater progress can be achieved by understanding better why some varieties are more productive or stress resilient than others. In the absence of detailed information on plant traits such as root architecture, breeders rely on chance combinations of favourable alleles. However, with inexpensive, rapid tools to assess genotypic differences in trait expression in the field, such as the measurement of root activity proposed here, the identification and selection of superior genotypes can be accelerated.

The project is consistent with the idea of sustainable intensification: wheat crops that use the available soil water to best effect are more productive and N efficient, thus minimising environmental impact on agricultural land, and reducing the area of land that needs to be cultivated to produce a tonne of grain. Thus, the project is consistent with the food security goals of the BBSRC.

The project will pave the way to a deeper understanding of root function. It is a rule of thumb that with access to new measurement technologies, scientific advance will follow. It is anticipated that by combining existing techniques with the development of new methods in the proposed work, project outcomes will be readily taken up by the scientific community.