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. Principle 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 (gs), A and NPQ and indicating that dynamic photosynthesis has adaptive value in O.glaberrima. Kinetics of NPQ, A and gs 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.

A ‘wiring diagram’ for source strength traits impacting wheat yield potential

“…Furthermore, recent studies focusing on characterizing the dynamic properties of photosynthesis (largely in controlled conditions) suggest that we may need to reconsider the way in which photosynthesis is measured to more accurately reflect the field conditions in which crops are grown. It has been previously shown that more natural variation is seen between genotypes during non-steady-state conditions than steady-state conditions, suggesting that our previous understanding of natural variation for photosynthetic traits may be underestimated ( Acevedo-Siaca et al , 2020 ; McAusland et al , 2020 ; Cowling et al ., 2022 ). It remains difficult to measure dynamic properties at a high throughput required for field screening, for example by using gas exchange, solar-induced fluorescence, or spectral reflectance; however, this is an active research area (reviewed in Murchie et al , 2018 ; Fu et al , 2022 ).…”

A ‘wiring diagram’ for sink strength traits impacting wheat yield potential

“…Furthermore, recent studies focusing on characterizing the dynamic properties of photosynthesis (largely in controlled conditions) suggest that we may need to reconsider the way in which photosynthesis is measured to more accurately reflect the field conditions in which crops are grown. It has been previously shown that more natural variation is seen between genotypes during non-steady-state conditions than steady-state conditions, suggesting that our previous understanding of natural variation for photosynthetic traits may be underestimated (Acevedo-Siaca et al, 2020;McAusland et al, 2020;Cowling et al, 2022). It remains difficult to measure dynamic properties at a high throughput required for field screening, for example by using gas exchange, solar-induced fluorescence, or spectral reflectance; however, this is an active research area (reviewed in Murchie et al, 2018;Fu et al, 2022).…”

“…Natural genetic variation for NPQ induction and relaxation can be found in wheat genotypes and wheat wild relatives, suggesting that a breeding approach may be possible for improvement (McAusland et al, 2020), and in rice (Cowling et al, 2022). In a similar way to Rubisco capacity and activation state, a canopy-dependent strategy may be necessary for further optimization since the capacity for protective NPQ seems to be greater in the lower, shaded, regions of the canopy where it is required for enhancement of photoprotection, as shown for rice (Foo et al, 2020).…”

Genetic variation in photosynthesis: many variants make light work

“… Sharwood et al (2022) review the great potential to find novel allelic variation in photosynthetic traits in large germplasm collections for food and fibre crops and their wild relatives, and how this variation could be leveraged to accelerate genetic progress in crop breeding programmes. Research on Oryza glaberrima (African rice) by Cowling et al (2022) provides a case in point. Whereas African rice is not suitable for commercial rice production due to lodging, shattering, and low yield, it makes an attractive target for gene mining for introgression into O. sativa indica and japonica .…”