The theory and applications of CRISPR in plant and tree improvement

© CAB International 2018. Increasing global population combined with a changing climate is placing pressure on global plant production systems, and rapid leafy and woody plant improvement is required to meet the demands of the future. Conventional breeding is time-consuming, especially in woody plants, and potential new plant traits are limited by the pre-existing genetic diversity. CRISPR/Cas genome editing (GE) technology allows rapid, simple and targeted modifications of plant genomes, as well as the introduction of novel genes into the germplasm. Both agrobacterium and ribonucleoprotein (RNP)mediated delivery of CRISPR/Cas components to plant cells can produce transgene-free edited plants, with F1 segregation required for the former. RNP-mediated editing in protoplasts can be directly used for gene editing without transgenes, and for pyramiding of desired genes into germplasm. However, plant regeneration from protoplasts remains to be established for many woody species. In addition, high rates of SNP occurrence in outcrossing species, as well as a shortage of functional genomics knowledge, increases the complexity of designing CRISPR/Cas editing pipelines. However, despite some challenges, CRISPR/Cas GE has seen widespread application in the generation of disease-resistant plants (providing resistance to fungal, bacterial and viral pathogens), as well as improving responses to abiotic stresses and increasing yields, amongst others. With the rapid development of new computational tools for designing and targeting CRISPR/Cas systems, increasing functional genomics knowledge, progress in protoplast-RNP-based editing and favourable regulatory outlook, CRISPR/Cas GE is close to providing a new generation of future-proofed woody and leafy plants.