Microspore embryogenesis in Citrus and in other fruit crops

Conventional methods, involving several generations of selfing, are not applicable to produce homozygous lines in Citrus as well as in the other fruit crops, due to the high heterozygosity of the genomes, the long duration of the generation cycle, the large size, and, often, the self-incompatibility. For this reason, there is no different way to obtain homozygosity in this kind of plants than “gametic embryogenesis” that allows the development of haploids (Hs, plants with gametophytic chromosome number) and doubled haploids (DHs, haploids that have undergone chromosome duplication) from heterozygous parents in a single step. Therefore, gametic embryogenesis is increasingly object of research for fruit breeders. There are several available methods to obtain Hs and DHs, and among them, microspore embryogenesis through in vitro anther or isolated microspore culture is the most effective and widely used. The aim of this report is to provide some background, recent advances and future prospective of the application of microspore embryogenesis to some fruit crops and particularly to Citrus.