Plant architecture and functioning of hybrid potato plants grown from true seeds versus seedling tubers : A quantitative study from leaf to crop

Summary

Potato is conventionally propagated clonally through seed tubers, which are vegetative storage organs. Recently, true potato seeds (TPS), the sexually propagated botanical seeds, have gained renewed interest due to advancements in diploid hybrid potato breeding. True seeds offer advantages such as reduced risks of diseases, easier storage and transportation, and rapid multiplication. Various propagule types can be derived from true seeds, including true seed transplants and seedling tubers (tubers derived from true-seed-grown plants), which are the primary planting materials used in hybrid potato systems. Interestingly, even grown from same genotype and same conditions, true-seed-grown and seedling-tuber-grown plants exhibit distinct growth and development patterns. The knowledge on these differences is highly relevant for hybrid potato breeding and cultivation yet remains limited. This thesis investigates the impact of propagule type on plant architecture, physiological responses, and their interactions under different environmental conditions. Greenhouse and field experiments were conducted using genetically identical hybrid potato plants grown from true seeds and seedling tubers. Differences between true-seed-grown and seedling-tuber-grown plants were quantified at multiple levels: leaf, stem, plant, and crop. Their different patterns in plant architectural development and biomass allocation were attributed to distinct temporal-spatial distribution of branches, resulting in a more branched and compact architecture in true-seed-grown plants compared to seedling-tuber-grown plants. However, under controlled conditions, leaf photosynthetic performance was not affected by these differences, with leaf age being the primary influencing factor. In the field, higher stem density reduced branching on individual main stems in both propagule types, with a stronger effect in true-seed-grown plants. At crop level, propagule type had a greater impact than stem density, influencing crop canopy development, resource allocation, and marketable yield. Findings from this research highlight the crucial role of plant architecture, particularly branching, in source-sink dynamics, a largely overlooked trait in potato research. This thesis also introduces a method to quantify plant architectural development, applicable to other species. The intrinsic differences between true seeds and seedling tubers underscore the importance of considering propagule type when assessing phenotypic traits, especially those linked to lateral branching. Future research should integrate multiple disciplines, including molecular biology, physiology, agronomy, and evolutionary biology, to further explore these distinctions. Additionally, the quantified variables in this thesis provide the foundation for an architecture-based potato model, addressing gaps in current potato modelling approaches. A combined experimental and modelling approach is recommended to enhance understanding of source-sink dynamics at multiple scales, ultimately informing potato breeding strategies for improved crop design.