Mechanisms of potato dormancy break: a metabolomics approach

Potato dormancy break is a commercially important process that leads to losses during crop storage. Dormancy release involves the activation of buds on the tuber surface. Although much is known about hormonal and environmental triggers for dormancy release, there is a lack of knowledge on the metabolic processes stimulated by these factors, enabling bud growth to occur. In this thesis I report on experiments designed to characterise and investigate the earliest metabolic changes occurring as tuber buds exit dormancy and start to sprout. The majority of previous work focused on changes in the tuber rather than the buds, due to their size limiting analysis. To tackle this problem, I have developed a mass spectrometry approach using individually dissected buds from tubers at different time points in storage, studying cultivars showing a range of genetically determined dormancy characteristics grown under both field and greenhouse conditions. These investigations identified elements of the citric acid (TCA) cycle as very early markers of bud release from dormancy across a range of storage and growth conditions for a diverse set of tuber cultivars. Moreover, a quantitative analysis indicated that at certain stages the TCA cycle was functioning in a non-cyclic manner, a phenomenon reported in other biological systems. These results provide an insight into the earliest metabolic events in tuber bud sprouting, providing lead markers that may be of interest to the industry as novel approaches to measuring tuber condition during storage. In the final part of the thesis I report on the development and application of a method to image metabolite distribution around tuber buds as they leave dormancy. An optimisation process is described which allows detection of TCA metabolites in sections of tubers, providing the foundation for future work analysing where and when shifts in TCA metabolites occur within tubers during bud sprouting. All the data presented in this thesis are available on request from Prof. Andrew Fleming, Department of Animal and Plant Sciences, University of Sheffield (contactable at a.fleming@sheffield.ac.uk)