Shaping plant architecture for improved productivity: Strigolactones and beyond

Feeding the growing world population is a primary concern faced by plant breeders and producers. The world population of 8 billion is expected to reach 9.8 billion by 2050, which will demand a 60% increase in food production. These demands need to be met under changing climatic conditions and already stretched resources by extending the boundaries of agriculture to urban areas, deserts, and fresh and saltwater bodies. Additionally, crops are needed to support deep space explorations. Therefore, plants with desirable stature, organization, better resource use efficiency, and higher yield are required to meet these targets. The food security challenge is not new; from prehistoric times, humans shaped plant architecture to make plants fit their needs. For example, intentional/unintentional selection in different plants led to the development of un-branched maize from branched teosinte, spikes with more to fewer inflorescence branches in barley and wheat, tall vine-like plants into compact bushes in tomato and soybean, and from tall to semidwarf varieties in wheat, barley, rice, and sorghum. However, control of plant architecture is complex, as several phytohormone-signal transduction pathways, besides other genetic and epigenetic factors, determine it. Among the plant hormones, strigolactones are vital in shoot branching and root growth, influencing the plant's architecture. Given the importance of shoot architecture in determining yield, we reviewed different traits defining plant architecture and genetic and physiological factors contributing to these traits with attention to wheat, barley, rice, and Arabidopsis. We hope the information will help develop crops with desired architecture for terrestrial and extraterrestrial farming.