Screening and performance of barley and wheat for improved phosphorus use efficiency (PhD)

The challenge

Concerns over dwindling supplies of good quality phosphate rock (PR), and geopolitical instability in those few countries with major PR deposits, may lead to a sharp increase in the cost of phosphorus (P) fertilisers. The EU has already placed PR on its list of critical raw materials. Additionally, there is increased pressure under the Water Framework Directive (WFD) to use P fertilisers more efficiently and lower the risk of P loss to water. Furthermore, seed phytate cannot be efficiently digested by non-ruminants, requiring additional feed inputs of available P or phytase to break down the phytate. Seed phytate also reduces the availability and absorption of certain essential micronutrients, including iron (Fe), zinc (Zn), calcium (Ca) and magnesium (Mg), in the body of animals and humans.

The project

This PhD seeks to reduce the P requirement of cereal crops through the use of more P-efficient cultivars. The vast majority of P taken up by arable crops is stored in plant tissues and later re-translocated to the developing seed where it accumulates as phytic acid (inositol hexaphosphate). However, recent calculations suggest that only a small proportion of the total P taken up by the plant (50-90 kg P2O5/ha) is actually required for photosynthesis (15-20 kg P2O5/ha), and that mass P storage in plant tissues may not be necessary on most UK soils with adequate soil P supply. Low P mutants have been identified in barley (lpa1-1) with good performance and reduced seed total P and are being developed in rice and wheat. A sulfate transporter gene (HvST) has been identified as the possible gene of interest resulting in low total P in grains. This project seeks to better understand the plant nutrient uptake patterns, metabolism and efficiency in current low P mutants and wild type varieties of barley in different soil P environments through pot experiments. Plant and grain tissue will be analysed for total P, phytic acid and micronutrients using verified methods. The project will also screen low P mutants of barley for further reductions in grain total P to ascertain that the low P trait is heritable through generations.

The HvST gene will be sequenced in the barley variety golden promise and used to develop mutants using CRISPR, a reverse genetics tool that knocks out genes of interest. Mutations will be detected in T0 barley plants following DNA extraction, purification and PCR amplification of the gene of interest using verified methods. The HvST gene sequence will also be used to BLAST the wheat TILLING website for similar mutations in wheat. Wheat varieties and landrace accessions will be obtained from the Germplasm Resources Unit (GRU) at the John Innes Centre and planted. DNA will be extracted from the wheat M0 generation and PCR amplification done to screen for possible mutations in the gene of interest. Screening for reduced total grain P will be done on the T1 and M1 barley and wheat populations.  

The benefits

This project will contribute to the development of novel and precise approaches to improved targeting of crop inputs and the development of more phosphorus efficient cereal cultivars through plant breeding. This research will provide AHDB and UK arable famers with the underpinning science on which to judge the feasibility of using P-efficient cultivars to reduce crop P demand and, therefore, future P fertiliser input costs. It will also help to reduce agriculture’s impact on water quality and help farmers meet the increasingly stringent requirements to improve local water quality, as well as improved animal and human nutrition.