Abstract
Simple Summary Harnessing the natural and induced diversity existing in plant genetic resources is fundamental for building future crops more sober in fertilizers, water, and pesticides that can cope with climate instability while yielding healthier and more nutritious products. The essence of plant breeding is to combine favorable traits in crossing parental varieties to select novel performing associations amongst the progenies. These associations are the product of recombination between the parental chromosomes occurring during meiosis, mainly by a reciprocal DNA exchange called Cross Over (CO). However, recombination does not occur randomly along the chromosomes, and COs are limited in number often hampering the desired associations of favorable traits. This review surveys the recent advances in methods for achieving a stimulation and/or a redistribution of meiotic COs along the parental chromosomes and targeting COs specifically at desired chromosomal sites. Reciprocal (cross-overs = COs) and non-reciprocal (gene conversion) DNA exchanges between the parental chromosomes (the homologs) during meiotic recombination are, together with mutation, the drivers for the evolution and adaptation of species. In plant breeding, recombination combines alleles from genetically diverse accessions to generate new haplotypes on which selection can act. In recent years, a spectacular progress has been accomplished in the understanding of the mechanisms underlying meiotic recombination in both model and crop plants as well as in the modulation of meiotic recombination using different strategies. The latter includes the stimulation and redistribution of COs by either modifying environmental conditions (e.g., T degrees), harnessing particular genomic situations (e.g., triploidy in Brassicaceae), or inactivating/over-expressing meiotic genes, notably some involved in the DNA double-strand break (DSB) repair pathways. These tools could be particularly useful for shuffling diversity in pre-breeding generations. Furthermore, thanks to the site-specific properties of genome editing technologies the targeting of meiotic recombination at specific chromosomal regions nowadays appears an attainable goal. Directing COs at desired chromosomal positions would allow breaking linkage situations existing between favorable and unfavorable alleles, the so-called linkage drag, and accelerate genetic gain. This review surveys the recent achievements in the manipulation of meiotic recombination in plants that could be integrated into breeding schemes to meet the challenges of deploying crops that are more resilient to climate instability, resistant to pathogens and pests, and sparing in their input requirements.