Pennacchi, João and Carmo-Silva, Elizabete and Parry, Martin (2017) Enhancing photosynthetic capacity and energy conversion in wheat. PhD thesis, Lancaster University.
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Abstract
Wheat is one of the major grain crops worldwide and provides approximately 20% of the total caloric and protein input for the world’s population. An increase in crop yields is required to meet the demands of the increasing world population in a challenging scenario of less predictable climatic conditions and sustainability requirements. There is an urgent need to develop crop plants that are more productive per land area and yield more stable outputs, without having to increase inputs of fertilizer or water. The canopy light-driven carbon uptake through photosynthesis is the primary determinant of plant biomass and yield. In this context, it is crucial to understand crop physiology and plant behaviour, with a focus on carbon balance, in contrasting environments, as well as to map the interactions between traits that drive wheat yields. Exploiting new methods of enhancing yield through successful strategies observed in other organisms can be used to achieve positive results for crop improvement. The impact of contrasting environments in wheat development and yield was studied in a panel of elite wheat cultivars over 3 seasons in UK. Late sowing and lower rainfall decreased the duration of grain development, impacting on grain yields. Yield stability was related to the crop resilience to shorter grain development periods and was partially explained by genetic similarities between cultivars or by the presence of genes related to crop development. The interaction between traits recognized as potential yield drivers and their stability and correlation to yield were studied in a double-haploid wheat mapping population. Traits correlated to light interception and use, and biomass allocation were strong yield drivers. Different lines adopt different strategies, based on these traits, to achieve high yields. The possible effect of the insertion of the ictB gene, related to carbon concentration in the chloroplast in cyanobacteria and to improved yields in plants, was studied in genetically modified wheat plants. No improvement was observed for photosynthetic traits or yield in the transgenic plants when compared to control plants, although unforeseen experimental problems could have hidden the expected phenotype. The achievements of this research contribute to improve the knowledge of wheat yield formation, its correlation to the carbon uptake process and stability in different climatic conditions. It may lead to a better understanding of new potential strategies to be applied in the breeding of genotypes for higher and more stable yields.