Doubled haploids in maize: Development, deployment, and challenges

Abstract Haploids are naturally produced in maize ( Zea mays L.) at different rates and can also be induced through different methods. Haploids are used to develop doubled haploids (DHs), which have many potential uses. The development of DH lines in maize involves haploid induction, haploid identification, chromosome doubling, and field sowing for self‐pollination of D 0 plants. Different potential methods are used for haploid induction, in‐vivo maternal haploid induction being the most prevalent. Haploid induction is highly reliant on the unambiguous identification of haploids among a mixture of different ploidies. Haploid identification is facilitated by visual morphological markers, chromosome counting, flow cytometry, molecular markers, and many other approaches. Chromosome doubling may be achieved by spontaneous doubling or by induction with different antimicrotubular treatments. Among the potential uses of DH lines are the development of inbred lines, genomic selection (GS), quantitative trait loci (QTL) mapping, and unlocking new genetic variations. Although DH technology can potentially accelerate maize breeding, it still faces challenges at each step of DH line development. This article aims to highlight the importance, procedural steps, potential opportunities, and key challenges in DH line development in maize.