Carotenoid Composition and Interaction with Dry Matter Across Spatial Variation and Developmental Time in Cassava (Manihot esculenta)

Vitamin A deficiency (VAD) is a major cause of blindness and increased mortality in sub-Saharan African children. While cassava (Manihot esculenta) is a major staple crop due to its adaptability to drought and poor soil conditions, its low nutritional value heightens micronutrient deficiencies. Yellow-fleshed cassava varieties accumulate provitamin A carotenoids, offering a sustainable strategy to combat VAD. Breeding nutritious cassava is challenged by a negative correlation between total carotenoids (TC) and dry matter (DM), compromising cassava’s desired qualities. This correlation is linked to a Phytoene synthase 2 (PSY2) variant in the carotenoid biosynthetic pathway, but whether it affects the traits through genetic linkage or pleiotropy is unclear. Analyzing variants with color differences between root layers, corresponding to TC accumulation, allows examining the TC/DM relationship across and within genotypes. This approach helps understand the trade-off beyond the PSY2 locus and test the hypothesis of an inherent physiological interaction rather than a single genetic linkage. We harvested roots of 20 African, Colombian, and hybrid accessions at four timepoints, separating inner and outer tissue layers to quantify DM and carotenoids (UPLC/UV-VIS). Linear models revealed that, after accounting for genotype, the negative impact of TC on DM increased over time. Principal component analysis showed that most variation in carotenoid composition was due by different partitioning between upstream beta-carotene and precursors (PC1) vs downstream xanthophylls & lutein (PC2). PC1 significantly negatively impacted DM after accounting for TC accumulation, suggesting that accumulation of certain carotenoids, like phytoene, may play a larger role in the TC/DM relationship. Understanding these interactions can aid identifying carotenoid regulatory processes, facilitating effective cassava biofortification strategies.

Interning at BTI has profoundly shaped my view of research by exposing me to diverse areas of plant science and providing valuable networking opportunities, learning about graduate school through unique perspectives. One key learning experience was being introduced to bioinformatics and data analysis through R, an initially challenging but rewarding tool I can incorporate to wet-lab work. I was fortunate to join Jean-Luc Jannink’s lab and be mentored by Seren Villwock. I am deeply grateful for her guidance and support, which has been the highlight of my summer, pushing me to become a better scientist and promoting my critical thinking skills. I also thank Kaitlin Diggins, my social mentor, for her invaluable insight and resources for my future steps. Though coming from Puerto Rico brought initial doubts and fears, Ithaca has been nothing but welcoming and I’ll forever cherish my time here, the people I’ve met, and my growth into a more confident and prepared scientist!