Genome editing in polyploid crops: progress, challenges, and prospects

Polyploid crops play a vital role in global food production and commercial agriculture. Polyploid plants, characterised by having multiple sets of chromosomes, include wheat (hexaploid or tetraploid), tobacco (tetraploid), cotton (tetraploid), potato (tetraploid), oilseed rape (tetraploid), and others. For example, common wheat (Triticum aestivum) is an allohexaploid species (2n = 6x = 42) comprising the A, B, and D subgenomes. Its high heterozygosity, together with extensive genomic duplication and functional redundancy, makes precise mutagenesis of all homologous genes particularly challenging. For traditional breeding methods, stacking of multiple alleles through hybridisation and multi-generation backcrossing is often time-consuming and inefficient, especially in polyploid crops, where recessive mutations in a single homozygote are often masked by other copies. The rise of genome editing technologies in recent years, particularly the CRISPR/Cas system, has provided unprecedented opportunities for precisely improving polyploid crops and resolving their functional genomics. This review systematically summarises the traits of polyploid plants and the applications of genome editing for their improvement. Furthermore, it discusses the promise of emerging CRISPR-based technologies, analyses the unique challenges posed by polyploid genomes, and outlines prospective research directions.