Genetic strategies for improving crop yields

Abstract

The current trajectory for crop yields is insufficient to nourish the world's population by 2050¹. Greater and more consistent crop production must be achieved against a backdrop of climatic stress that limits yields, owing to shifts in pests and pathogens, precipitation, heat-waves and other weather extremes. Here we consider the potential of plant sciences to address post-Green Revolution challenges in agriculture and explore emerging strategies for enhancing sustainable crop production and resilience in a changing climate. Accelerated crop improvement must leverage naturally evolved traits and transformative engineering driven by mechanistic understanding, to yield the resilient production systems that are needed to ensure future harvests.

Fig. 1 |. Predicted national-scale yield loss for maize, rice, wheat and soybean.

a–c, Maps indicate the yield losses caused by aridity stress averaged from 1950–2000 (a), heat stress averaged from 1994–2010 (b) and nutrient stress in 2009 (c). National data for each crop were previously compiled, and are here averaged and re-plotted using the maps package in R. d, Number of large flood events from 1985 to 2010 by country.

Fig. 2 |. Paths to increased crop yield in suboptimal environments.

Overview of traits that provide increased resilience and yield in variable environments. a, Pathogen recognition by cell-surface and intracellular receptors (resistance proteins). Manipulation of host cells by pathogen-secreted effectors to promote infection can be recognized by resistance proteins and converted to disease resistance.b, Flooding survival via opposing regulation of gibberellin (GA). Semidwarf 1 (SD1), Snorkel 1 and Snorkel 2 (SK1/2) confer escape by accelerated elongation growth. Submergence 1A (SUB1A) confers tolerance by quiescence of growth. c, Root growth towards moisture involves transcriptional regulators (indol-3-acetic acid inhibitor protein 3 (IAA3) and auxin response factor (ARF7)), and is regulated by the hormones ABA and auxin. d, HKT1 (high-affinity K⁺ transporter sub-family 1) mediates sodium (Na⁺) exclusion from leaves. e, In developing seed tissues, catabolism of T6P aids the movement of photo-assimilate carbohydrate (CHO) from leaves to sinks in developing florets. f, Optimizing photosynthetic light harvesting and CO₂ fixation by altering photosynthetic protein abundance and minimizing photorespiration. PS, photosystem. g, Dynamic control of stomatal aperture by pairs of epidermal guard cells lessens desiccation. h, Symbiotic plant–microorganism interactions facilitate the uptake of essential nutrients. NH₄⁺, ammonium; PO₄⁻, phosphate; NO₃⁻, nitrate.

Fig. 3 |. Targets for improving the efficiency of photosynthesis and primary carbon metabolism that have experimental support for success.

Transgenic manipulations of photosynthetic metabolism that lead to improved photosynthetic efficiency include (1) improving photosynthesis in a dynamic light environment by accelerating recovery from a photoprotected state, by overexpressing enzymes (such as photosystem II subunit S (PSBS) and VDE) that are involved in non-photochemical quenching (NPQ) (the dissipation of excess excitation energy as heat); (2) altering the CO₂ response of stomata or the density of stomata on the leaf surface to increase the efficiency of water use^,,; (3) increasing the capacity for mesophyll conductance of CO₂; (4) improving the energy efficiency of carbon metabolism by altering mitochondrial enzymes; (5) optimizing investment in light collection; (6) increasing electron flow through the photosynthetic electron transport chain; (7) altering Rubisco properties and activation to increase CO₂ assimilation^,; (8) bypassing photorespiration; and (9) increasing the efficiency of ribulose 1,5-bisphosphate (RuBP) regeneration.