Genetic Diversity in Nitrogen Fertiliser Responses and N Gas Emission in Modern Wheat

Understanding the Physiological and Molecular Basis for Differences in Nitrogen Use Efficiency in the Parents of a Winter Wheat MAGIC Population

The need to improve both the cost of food production and lower the environmental impact of food production is key to being able to sustainably feed the projected growth of the human population. To attempt to understand how to improve yields under lower nitrogen (N) inputs, a diverse set of UK winter wheats encompassing ~80% of the genetic diversity in current winter wheats in the UK were grown under a range of N levels and their performance measured under various levels of N. This population has parents which encompass all four end-use categories to understand how breeding for differences in NUE may change across different end-use types of wheat. The growth of the eight parents of a MAGIC population showed significant differences in biomass per plant, ear number, yield and protein content of the grain when grown with differing levels of N. No consistent response to N was seen for the lines tested for all of the traits measured. However, the underlying difference in response to N was not due to N uptake or N translocation, as short-term 15N uptake and translocation showed no significant differences in the lines tested. RNASeq was then performed on two different bread-making varieties grown under low-N conditions to identify putative genes controlling the underlying differences seen in biomass production when grown on low N. This led to the identification of the genes involved in growth and C/N signaling and metabolism, which may explain the differences in growth and biomass production seen between the parents of this population.

Novel molecules and target genes for vegetative heat tolerance in wheat

To prevent yield losses caused by climate change, it is important to identify naturally tolerant genotypes with traits and related pathways that can be targeted for crop improvement. Here we report on the characterization of contrasting vegetative heat tolerance in two UK bread wheat varieties. Under chronic heat stress, the heat-tolerant cultivar Cadenza produced an excessive number of tillers which translated into more spikes and higher grain yield compared to heat-sensitive Paragon. RNAseq and metabolomics analyses revealed that over 5000 genotype-specific genes were differentially expressed, including photosynthesis-related genes, which might explain the observed ability of Cadenza to maintain photosynthetic rate under heat stress. Around 400 genes showed a similar heat-response in both genotypes. Only 71 genes showed a genotype × temperature interaction. As well as known heat-responsive genes such as heat shock proteins (HSPs), several genes that have not been previously linked to the heat response, particularly in wheat, have been identified, including dehydrins, ankyrin-repeat protein-encoding genes, and lipases. Contrary to primary metabolites, secondary metabolites showed a highly differentiated heat response and genotypic differences. These included benzoxazinoid (DIBOA, DIMBOA), and phenylpropanoids and flavonoids with known radical scavenging capacity, which was assessed via the DPPH assay. The most highly heat-induced metabolite was (glycosylated) propanediol, which is widely used in industry as an anti-freeze. To our knowledge, this is the first report on its response to stress in plants. The identified metabolites and candidate genes provide novel targets for the development of heat-tolerant wheat.