Advances in doubled haploid technology of oilseed rape

Doubled haploid (DH) breeding through anther/microspore culture provides breeders with the quickest and most reliable tool to produce homozygous diploids in many crop species including oilseed rape. The DHs can be employed efficiently in mutation breeding, gene transformation, generation of purelines and mapping populations, and rapid screening for complex traits like drought, cold and salinity tolerance. In recent past, attempts have been made globally in several directions with an objective to increase the proportions of the DHs regenerated. Researches have been done on various factors influencing microspore embryogenesis and haploid regeneration such as donor plant genotype and conditions, pretreatment, anther/microspore stage, culture media and environment, and diploidization etc. In general, plants grown under controlled environmental conditions such as glasshouse or polyhouse, yellowish green-colored anthers, mid- to late-uninucleate stage of pollen to be cultured, cold stress pretreatment of microspores coupled with colchicine/antiauxin treatment, and immediate colchicine application to isolated microspores appear to be the most optimum requirements for achieving the highest success with respect to microspore embryogenesis and diploidization in Brassicas. During the last two decades, significant developments in haploid production techniques have resulted in greater interest in their application in rapeseed-mustard improvement programme. Efforts are underway for the development of more efficient protocols which would further improve the regeneration and diploidization frequencies in cultured microspores of Brassica, thereby making DH technology a routine tool for wider applications in rapeseed improvement programmes. This review focuses on recent developments in DH technology in oleiferous rape.