PLANT CELL BIOTECHNOLOGY AND MOLECULAR BIOLOGY

Doubled haploid (DH) technology represents a major advancement in plant breeding, offering a rapid and efficient method to produce completely homozygous lines in a single generation. This approach significantly shortens breeding cycles and enhances genetic gain by accelerating the fixation of desirable traits. DH lines have become indispensable in hybrid development, molecular breeding, quantitative trait loci (QTL) mapping, genomic selection, and functional genomics. The technology encompasses both In vivo methods, such as haploid inducer lines and genome elimination, and In vitro methods like anther, microspore, and ovule culture. Key genetic components such as MTL, DMP, and CENH3 play critical roles in haploid induction, and recent advances in CRISPR-Cas systems have enabled simultaneous genome editing and DH line creation. Despite its advantages, DH technology faces limitations including genotype dependency, low efficiency in some crops, technical complexity, cost, and challenges in chromosome doubling and plant regeneration. Moreover, the use of transgenic haploid inducers raises biosafety and regulatory concerns. Integration with modern tools such as speed breeding, artificial intelligence, synthetic biology, and high-throughput phenotyping has improved the scalability and precision of DH systems. Applications now extend beyond major crops to include recalcitrant and orphan species, supporting climate-resilient breeding efforts. Machine learning models are increasingly used to predict haploid induction success, embryo viability, and breeding values from large genomic datasets. Automation in embryo rescue, chromosome doubling, and screening is also enhancing throughput and reducing labour. As the global demand for food and climate-resilient crops intensifies, DH technology continues to be a critical component of next-generation breeding programs. Synthesis of DH methods, molecular mechanisms, applications, challenges, and future prospects aimed at maximising the potential of this technology in crop improvement. Case studies on major crops revealed that in maize, DH technology has become an integral part of commercial breeding. In Brassica napus, microspore culture is the preferred DH method due to its high efficiency and scalability. In Capsicum annuum (pepper), anther culture has been employed to develop DH lines for hybrid seed production and disease resistance breeding. The success of haploid and doubled haploid (DH) technologies often hinges on the genetic background of donor plants. It was emphasised that as global food demand rises, DH technology remains pivotal for delivering resilient, high-yielding cultivars with enhanced genetic gains under changing climatic conditions.