EXPLORING MOLECULAR MECHANISMS SHAPING ROOT GROWTH ANGLE IN CEREALS

Global food security and climate change represent major challenges faced by humankind during this century. Developing crops that have more resource efficient roots is an attractive solution to increase crop production sustainably whilst also enhancing soil carbon sequestration, and tolerance to stresses. The aim of my work during my PhD was to: - Identify key genes that control architectural root traits contributing to deeper rooting in cereal crops such as wheat and barley. - Introduce an improved ROS protocol which provides new insights on exploring the relationship between root architecture and reactive oxygen species (ROS) in cereal seedlings. This PhD thesis is organised in 3 chapters in which: • Chapter I: I describe the adaptation of root system architecture to environmental cues exploring advantages to set steep vs shallow rooting system. Genetic control of gravitropic and anti-gravitropic mechanisms setting the root angle in both dicots (as shown in Lombardi et al., 2021), and monocots are discussed. • Chapter II: I present an improved ROS measurement protocol developed to facilitate spatial quantification of ROS in the root tips of cereal seedlings. The relationships between ROS and architectural root traits, as well as between ROS and hormones, are explored in these cereal seedlings. • Chapter III: I report the work (Fusi et al., 2022) providing new insights on a putative component of an Anti-Gravitropic Offset (AGO) mechanisms. A genetics approach was used to characterize root angle or root length in mutants of the barley TILLMore population. Whitin this population one mutant with a disrupted gene HvEGT1 (Enhanced Gravitropism 1) regulating root gravitropic set point angle in cereals was characterized. Barley and wheat mutant lines disrupting EGT1 function exhibited a deeper rooting phenotype, revealing this sequence as a promising gene target to create novel cereal varieties.