Meiotic crossover reduction by virus-induced gene silencing enables the efficient generation of chromosome substitution lines and reverse breeding in Arabidopsis thaliana.

Several meiotic mutant phenotypes were described for which plant breeding applications were proposed, like the in- or decrease of crossover (CO) recombination rates. However, recessive meiotic mutations in breeding lines may affect fertility or have other pleiotropic effects, because of which transient silencing techniques may be preferred. Reverse breeding is a breeding technique that would benefit from transient downregulation of CO formation. The technique is essentially the opposite of plant hybridization: a method to extract parental lines from a hybrid. The method can also be used to efficiently generate chromosome substitution lines (CSLs). For successful reverse breeding, the two homologous chromosome sets of a heterozygous plant must be divided over two haploid complements, which can be achieved by suppression of meiotic CO recombination and the subsequent production of doubled-haploid plants. We here show the feasibility of transiently reducing CO formation using virus-induced gene silencing (VIGS) by targeting the meiotic gene MSH5 in a wild-type heterozygote of Arabidopsis thaliana. The application of VIGS (rather than using lengthy stable transformation) generates transgene-free offspring with a desired genetic composition: we obtained parental lines from a wild-type heterozygous F1 in two generations. In addition, we obtained 20 (of the 32 possible) CSLs in one experiment. Our results demonstrate that meiosis can be modulated at will in A. thaliana to rapidly generate CSLs and parental lines for hybrid breeding. Furthermore, we illustrate how the modification of meiosis using VIGS can open routes to develop efficient plant breeding strategies.