REVIEW OF RESEARCH AT FRUITTEELTCENTRUM ON THE PRODUCTION OF HOMOZYGOUS PLANTS THROUGH ANDROGENESIS IN VITRO AND PARTHENOGENESIS IN SITU

Formation of homozygous embryos remained one of the major limitations for all techniques. For anther and microspore culture, physical and chemical treatments improved embryo induction and/or microspore divisions. In microspore culture, pro-embryos were blocked in further development. Embryo yield was more promising in anther culture but plant regeneration was not yet optimal. For parthenogenesis in situ, embryo production, determined by fruit set, seed set and embryo set, was the main bottleneck to come to a feasible protocol. These parameters were strongly influenced by irradiation of pollen (100– 500 Gy) and, to a less extent, picking time of the fruits (90– 152 days after pollination). Regeneration of putative homozygous plants was also influenced by irradiation dose, picking time and also by cold treatment of the embryos (0– 18 weeks). The homozygous nature of all plants obtained through anther culture and parthenogenesis in situ, was evaluated by analysis of the hetero-allelic-S-gene. Plants obtained by parthenogenesis in situ can be also the result of self-fertilisation. To exclude such plants, seggregating AFLP markers for each chromosome pair are searched. All plants ex vitro are di-, tri- or tetraploid. The first homozygous plants flowered in 1998.

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