Improving abiotic stress tolerance to adapt sorghum to temperate climatic regions

Abstract

Sorghum is a genus consisting of many species in different levels of domestication, comprising wild [e.g. S. arundinaceum], weedy [e.g. S. halapense] and domesticated ones [e.g. Sorghum x almum, S. sudanense, S. bicolor]. Sorghum bicolor [L.] Moench is the fifth most important cereal crop globally. It shows a remarkable diversity, including five different subspecies and their intermediates, and several crop types like grain, forage, sweet and broomcorn (Hariprasanna and Patil, 2015). Although it originates in the tropics of Africa, the remarkable scope of genetic diversity among the different subspecies has conferred an extraordinarily broad adaptability and a highly versatile range of end-uses (Boyles et al., 2019). Sorghum has a particular advantage over crops like maize in extreme climates, where it achieves superior yields to maize (Farré and Faci, 2006; Staggenborg et al., 2008). Although sorghum is a major subsistence crop worldwide and an important component of industrial agriculture, it is frequently considered as an orphan crop (Boyles et al., 2019) and breeding progress has been considerably slower than most major global crops.Despite its enormous potential and broad adaptive diversity, breeding to adapt sorghum for agricultural use in temperate Europe has progressed only slowly so far. Until recently, conventional breeding methods were the primary approach for genetic improvement of sorghum. These were mainly based on selection by visual phenotyping accompanied by introgression of desirable traits into elite germplasm. As in the early stages of classical breeding in most crops, these classical approaches present strong challenges to overcome linkage drag and maintain useful diversity in chromosome regions carrying essential adaptation genes under strong selection