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Maize is one of the most important crops in the world and is also an essential raw material for the food, fuel, and fodder industries. Maize hybrids are widely used today, and gain of elite inbred lines is a crucial step for hybrid breeding. Doubled haploid (DH) technology based on in vivo haploid induction (HI) is often used to accelerate the efficiency of breeding of maize and other crops (Ishii et al., 2016). Maize is a typical diploid plant (2n= 20) with a very low rate (0.1%) in producing haploid (2n= 10) naturally. In vivo HI by inducer line Stock6 can lead to maternal haploid with a rate of 1%–2% when it is used as pollinator (Coe, 1959). Stock6-derived inducers have been considered as the most effective method for DH breeding in maize.

Although the phenomenon of Stock6-induced haploidy was discovered 50 years ago, the genetic and biological mechanism of HI is still unclear. Several quantitative trait loci (QTLs …