Haploid and Doubled Haploid Technology

The microspore culture technique has its wide applications in plant genetic research and breeding programmes in oilseed Brassicas due to its relative simplicity, efficiency in haploid and doubled haploid production, mutation and germplasm generation, and gene transformation. Various factors could influence microspore embryogenesis and haploid production including donor plant genotype, donor plant physiology, microspore developmental stage, culture conditions, culture environment and pretreatments. Stress is also an essential component during embryogenesis induction in microspore culture. Efficient plant regeneration from microspores mostly occurs through direct embryogenesis ensuring minimal occurrence of cytogenetic abnormalities. Appropriate stress conditions such as chilling, partial desiccation, cotyledon excision, and successive subculture of microspore-derived embryos could promote plant development in oilseed rape. Medium renovation, phytohormones and plant growth regulators, and chromosome doubling agents such as colchicine treatment also affect plant regeneration in Brassica species. Compared to colchicine treatments of microspore-derived embryos and plants, immediate colchicine treatment of isolated microspores results in high embryogenesis and diploidisation and low chimeric percentages. The ploidy level of microspore-derived plants of Brassica species could be estimated by different methods at various stages. Mutation breeding techniques are widely used in plant breeding for producing useful mutants and variants. Microspore culture also provides an ideal method for mutation because the mutated traits can be fixed in homozygous condition by chromosome doubling, which can enforce to obtain target mutation traits efficiently. Ultraviolet irradiation, mutagenic agents ethyl methane sulphonate and sodium azide could be applied to isolated microspores and the derived embryos of rapeseed. Utilization of microspore-derived embryos for production of desired traits such as the altered fatty acids, disease resistance and glucosinolate compositions through mutagenesis and selection is advancing and also discussed.