Plant breeding at the speed of light: the power of CRISPR/Cas to generate directed genetic diversity at multiple sites

Abstract

Classical plant breeding was extremely successful in generating high yielding crop varieties. Yet, in modern crops, the long domestication process has impoverished the genetic diversity available for breeding. This is limiting further improvements of elite germplasm by classical approaches. The CRISPR/Cas system now enables promising new opportunities to create genetic diversity for breeding in an unprecedented way. Due to its multiplexing ability, multiple targets can be modified simultaneously in an efficient way, enabling immediate pyramiding of multiple beneficial traits into an elite background within one generation. By targeting regulatory elements, a selectable range of transcriptional alleles can be generated, enabling precise fine-tuning of desirable traits. In addition, by targeting homologues of so-called domestication genes within one generation, it is now possible to catapult neglected, semi-domesticated and wild plants quickly into the focus of mainstream agriculture. This further enables the use of the enormous genetic diversity present in wild species or uncultured varieties of crops as a source of allele-mining, widely expanding the crop germplasm pool.

Keywords: CRISPR/Cas; Genetic diversity; Genome engineering; Plant breeding.

Fig. 1

Editing of cis-regulatory elements for the generation of dosage effect alleles. In contrast to conventional editing of coding sequences, editing of cis-regulatory elements enables the fine-tuning towards optimal gene expression level. Red colour indicates repressive, green colour activating transcription factors. Red Triangles indicate CRISPR cleavage sites. Orange sections indicate CRISPR/Cas-induced mutations

Fig. 2

De-novo domestication of tomato by CRISPR/Cas9-mediated multiplex editing. By simultaneously editing four genes involved in plant architecture (SP), flowering time (SP5G) and fruit size (SlCLV3 and SlWUS), Li et al. [57] achieved accelerated domestication of wild tomato. Figure design according to Li et al. [57]