Out of Africa: characterizing the natural variation in dynamic photosynthetic traits in a diverse population of African rice (Oryza glaberrima)

Abstract

African rice (Oryza glaberrima) has adapted to challenging environments and is a promising source of genetic variation. We analysed dynamics of photosynthesis and morphology in a reference set of 155 O. glaberrima accessions. Plants were grown in an agronomy glasshouse to late tillering stage. Photosynthesis induction from darkness and the decrease in low light was measured by gas exchange and chlorophyll fluorescence along with root and shoot biomass, stomatal density, and leaf area. Steady-state and kinetic responses were modelled. We describe extensive natural variation in O. glaberrima for steady-state, induction, and reduction responses of photosynthesis that has value for gene discovery and crop improvement. Principal component analyses indicated key clusters of plant biomass, kinetics of photosynthesis (CO₂ assimilation, A), and photoprotection induction and reduction (measured by non-photochemical quenching, NPQ), consistent with diverse adaptation. Accessions also clustered according to countries with differing water availability, stomatal conductance (g_s), A, and NPQ, indicating that dynamic photosynthesis has adaptive value in O. glaberrima. Kinetics of NPQ, A, and g_s showed high correlation with biomass and leaf area. We conclude that dynamic photosynthetic traits and NPQ are important within O. glaberrima, and we highlight NPQ kinetics and NPQ under low light.