Highly reactive chemicals meet haploidization

The ability to generate (di)haploid plants has provided a strategy to significantly accelerate the crop-breeding process. The major advantage of doubled haploids to breeders lies in the simultastep. Hence, each doubled haploid (DH) represents a pure line that can be further evaluated for the range of agronomically important traits. Haploids have been induced mainly through the generation of plants from cultivated gametophytic (haploid) cells, i.e., in vitro haploid technologies, or through the selective loss of one parental chromosome set upon inter- or intraspecific hybridization, i.e., in vivo haploid induction. However, in many crop species, efficient haploid technology is not yet available or only applicable to a limited number of genotypes (reviewed by Jacquier et al., 2020). Due to the limits and costs of current haploid technologies, plant breeders are highly interested in any methodological improvements. An efficient DH production system with low genotype dependency based on the in vivo approach exists so far only in maize. The haploid-inducing capacity of the inbred line Stock6, originally reported to cause haploid induction rates of 2.3%-3.2% (Coe, 1959), was further increased to above 8% in various inducer breeding programs (reviewed by Jacquier et al., 2020). The underlying genetics of the in vivo haploid induction process is quite complex. However, in recent years significant advances have been made in elucidating the major players.

Automated summary

The ability to generate (di)haploid plants has significantly accelerated the crop-breeding process, with each doubled haploid representing a pure line for further evaluation of agronomically important traits. While haploids can be induced through in vitro or in vivo methods, many crop species still lack efficient haploid technology.