In vivo maternal haploid induction in tomato.

Tomato (Solanum lycopersicon) is the second largest vegetable crop and the largest fruit crop (Costa and Heuvelink, 2018). Progress in tomato breeding has been achieved by classical breeding, introgression of traits found in related wild Solanum species and exploiting heterosis in F1 hybrid crosses (Lin et al., 2014). These approaches require the development of inbred lines to reduce or largely eliminate heterozygosity. Classically, multiple rounds of selfing or backcrossing are used to generate inbred lines (Gale, 1980), but homozygous lines can also be obtained in a single generation using doubled haploid (DH) technology (Jacquier et al., 2020). However, tomato is highly recalcitrant for haploid induction (HI) (Segui-Simarro, 2010).