Complex trait analysis in the autotetraploid potato and the response of the potato cell wall to abiotic and biotic stress

Ponce Travezaño, Olga Patricia (2023). Complex trait analysis in the autotetraploid potato and the response of the potato cell wall to abiotic and biotic stress. University of Birmingham. Ph.D.

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Abstract

Potato is important for food security due to its nutritional value and ability to grow in diverse environments around the world. However, its productivity is highly affected by two principal stressors: late blight caused by \(\textit{P. infestans}\) and drought. Previous analyses described the dynamic role of the plant cell wall in growth and development,and its response to various external factors, including biotic or abiotic stresses. Indeed, it is the first barrier that pathogens must cross to successfully infect the plant, while modulation of components to fortify the cell wall is important for stress tolerance. Nevertheless, there is a need to understand in more detail how the dynamic response of individual cell wall components influences stress tolerance in potato varieties.

This thesis employs glycome and transcriptomic analyses in varieties with contrasting tolerance phenotypes to identify genes and cell wall components associated with tolerance or resistance of potato varieties to \(\textit{P. infestans}\) and drought stress. For both types of stress, there were tolerant-specific responses, but also many commonalities in the response of tolerant and susceptible varieties, although tolerant varieties tended to mount a stronger and faster response, which is likely crucial. Pre-existing differences in gene expression and cell wall composition were also widespread and likely prepare the tolerant varieties to enable a more effective response when the stressor arises. Key differences relating to the pectin component of the cell wall included higher levels of pectin methylesterification in tolerant varieties before stress and its effective modification in response to stress to strengthen cell wall structure or release cell wall fragments to stimulate an immune response. Key commonalities in the response of tolerant varieties to both types of stress included upregulation of an expansin gene and stronger upregulation of genes involved in lignin synthesis. An important goal in future work will be to relate such changes to guard cell development and the regulation of stomatal opening/closure, a key component of the response to both types of stress.

Ultimately, an improved understanding of the response to stress paves the way for the development of cultivars with improved stress resistance and yield stability under stress. However, since its genome is autotetraploid, there remain many challenges for genetic analysis and/or manipulation of complex traits in potato. Therefore, the final part of this project presented in “Appendix - Linkage disequilibrium” provides a theoretical exploration of one of the key concepts for genome-wide association analyses (linkage disequilibrium) in autotetraploid genomes, addressing its symmetry and dependence on key features of an autotetraploid meiosis.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):