International Journal of Agriculture Extension and Social Development

author(s)
Nilesh Ninama, Hemant Kumar Meena and Deepanshi Deora

abstract
Haploid and doubled haploid (DH) technologies provide powerful tools to accelerate vegetable breeding by creating completely homozygous lines in a single generation. Haploids are plants with a single set of chromosomes (gametophytic or monoploid number), and when their chromosomes are doubled, fully homozygous diploids (doubled haploids) are obtained. These methods, first demonstrated nearly a century ago by plant scientists like A.F. Blakeslee (Datura haploids, 1922) and S. Guha and S.C. Maheshwari (anther-culture haploids, 1964), significantly reduce the breeding cycle. Conventional inbreeding often requires 6-8 generations to achieve similar homozygosity, whereas DH techniques accomplish this in one step. In vegetables, haploid production can be achieved by several approaches (e.g. pollen or ovule culture, wide crosses and irradiated pollen) and is followed by chromosome doubling (commonly using agents like colchicine). This fast-track approach has been applied to many vegetable crops worldwide (tomato, pepper, onion, Brassicas, cucurbits, carrot, potato, etc.), enabling rapid development of uniform inbred lines, hybrid parents, and mapping populations. DH technology brings advantages such as time savings, uniform progeny, and ease of fixing recessive traits, but also faces challenges (genotype dependence, specialized lab requirements, occasional aneuploidy). This comprehensive overview covers the definitions, historical milestones, various induction methods, chromosome doubling techniques, applications in vegetable breeding, and the relative merits of haploid breeding. It highlights how haploid and doubled haploid approaches offer a fast-track to developing improved vegetable cultivars globally.