Pale-green mutants as potential breeding material to enhance the light energy conversion efficiency in barley

Over the past century, improvements in crop productivity have largely neglected photosynthetic traits. However, recent advances in photosynthesis understanding and genetic engineering present new opportunities to enhance crop performance by targeting these traits. One approach is to modulate photosystem antennae size to improve photosynthetic efficiency. Reduced leaf chlorophyll content, or a pale-green phenotype, has been shown to enhance photosynthesis and biomass in certain plants. This study investigates the effects of reduced leaf chlorophyll content on barley. By screening chemically-induced barley mutant populations, I identified six mutant lines with reduced chlorophyll content but normal or improved photosynthetic efficiency. Six distinct mutations responsible for the pale-green phenotypes were identified, most affecting chlorophyll biosynthesis genes, while one mutation involved the cpSRP54 protein gene. The pale-green phenotypes were inherited monogenically recessive-like. Specifically, the CHLI subunit mutation affected ATP hydrolysis necessary for chlorophyll biosynthesis, leading to cold sensitivity and altered chlorophyll biosynthesis pathways in the TM2490 line. Despite this, some mutant barley lines showed stable photosynthetic machinery and plant growth, making them candidates for future breeding programs and field trials, aiming to optimise barley yield and straw quality for bio-economy applications such as bio-fuels and bio-based products.