A high yield potential ideotype for irrigated rice: rice plant types with short culms and long, upright leaves

Abstract

ContextEnhancing crop yield can be achieved through two combined approaches: increasing photosynthetic biomass productivity and efficiently transferring photosynthetic products to the harvestable organs. Dwarfing has become a significant breeding objective due to benefits such as lodging resistance, improved grain allocation of photosynthetic products, and high nitrogen use efficiency. However, the commonly used gibberellic acid-deficient dwarf mutation (sd1) reduces leaf area and increases leaf area density, impeding photosynthetic biomass production. ObjectiveThis review proposes a plant type with a short culm and long, upright leaves to address the issues caused by the sd1 mutation, while maintaining the benefits of dwarfing. MethodsMethods used here are based on existing breeding practices and research findings, focusing on the characteristics of a plant type with a short culm and long, upright leaves. This review discusses the aspects of photosynthetic biomass productivity, sink strength of spikelets, accumulation and the effects of pre-heading non-structural carbohydrates (NSC) reserves. Since many significant earlier reports were published in Japanese and Chinese, this paper will devote substantial space to introducing them. ResultsBreeders have demonstrated that a plant type with a short culm and long, upright leaves can significantly increase grain yield. Generally, this type with lower positioning of the panicle within the canopy lowers the center of gravity and reduces leaf shading. Nevertheless, this plant type possesses other, less recognized, complex factors contributing to its high yield. These include mitigating the drawbacks associated with dwarfing, which are detrimental to photosynthetic biomass production. This type can also increase spikelet and NSC reserves during the heading stage, the former is related to sink size while the latter is associated with sink activity. ConclusionThe proposed plant type successfully balances the benefits of dwarfing with improved photosynthetic biomass production. It addresses the issues associated with the sd1 mutation, leading to enhanced grain yield and overall productivity. Implications or significanceThis review highlights the novelty of using a plant type with short culms and long, upright leaves to improve grain yield. It provides a significant advancement in crop improvement practices by maintaining the benefits of dwarfing while enhancing photosynthetic efficiency. The study also emphasizes the importance of considering complex eco-physiological factors, contributing to a more holistic approach in field crops research and practice. The development and testing of plant types with short culms and long upright leaves remains an important target for rice improvement programs in future, and this is discussed.