Improving Photosynthetic Efficiency and Climate Resilience in C4 Crops through Molecular Breeding: A Review

Abstract

C₄ crops such as maize, sorghum, pearl millet and sugarcane underpin food, feed and bioenergy production in warm regions, yet heat, drought, high vapour pressure deficit and changing atmospheric CO₂ threaten the efficiency of their photosynthesis. This review synthesises published evidence on the effects of climate stress on the C₄ pathway, the photosynthetic traits associated with resilience, the genetic regulation of those traits, and the use of molecular breeding and genome engineering to improve them. Comparative evidence from maize, sorghum, pearl millet and sugarcane, the role of Setaria as a C₄ model, and the translation of leaf-level gains into yield are also considered. The literature indicates that Rubisco content, electron transport, stomatal behaviour, photoprotection and recovery after stress are tractable targets, that genome-wide association studies have begun to link such traits to genomic regions, and that most candidate genes still await functional validation and field testing. Coordinated modification of co-limiting steps, evaluated in both stress and non-stress environments, emerges as the most credible strategy for stabilising yield under climate change. The main gaps are functional validation of candidate genes, studies of combined stresses beyond maize, and field testing of leaf-level gains.