Haploids and Doubled Haploids in Fruit Trees

Haploid and doubled haploid (DH) production provides a particularly attractive biotechnological tool in breeding of perennial crop species, such as fruit trees. Haploids (plants with a gametophytic chromosome number) and doubled haploids (haploids that have undergone chromosome duplication) reduce the time needed to produce homozygous lines compared to conventional breeding. In fruit crops, characterized by high heterozygosity, long generation cycle times, large size, and (often) self-incompatibility, there is no other way to produce homozygous breeding lines through conventional methods that involve several generations of selfing. Gametic embryogenesis, enables the development of haploids and double haploids from heterozygous parents in a single step, and is therefore increasingly the object of research for fruit breeders. This chapter provides the current status of research on doubled haploid production in many fruit crops: Actinidia deliciosa, Annona squamosa, Eriobotrya japonica, Carica papaya, Citrus, Feijoa sellowiana, Malus domestica, Morus alba, [Musa balbisiana (BB)], Prunus armeniaca, Prunus avium, Prunus domestica, Prunus persica, Pyrus communis, Pyrus pyrifolia, Olea europaea, Opuntia ficus-indica, Vitis vinifera.