RESTRICTIONS OF THE EFFICIENCY OF HAPLOID PLANT-PRODUCTION IN APPLE CULTIVAR IDARED, THROUGH PARTHENOGENESIS IN-SITU

For haploid plant production in Idared apple, parthenogenesis in situ was induced by irradiated pollen. The most important restrictions were seed set, embryo germination and green plant recovery from germinated embryos. The efficiency of green plant production was strongly influe nced by irradiation dose, picking time and quality of the irradiated p ollen. 250 Gy pollen was more efficient for green plant production tha n 500 Gy pollen. Using 250 Gy pollen with reduced germination capacity resulted in a five-fold lower green plant yield. Delaying picking of the fruits (140 instead of 70 days after pollination) had a significan t positive effect. Up to 20 plants per 1000 pollinated flowers, showin g no expression of a marker gene present in the pollen parent, were ob tained in some treatments. Induction efficiency was high when seed wei ght was high. This offers the possibility of selecting seeds with the best chances for haploid plant production. Heavy seeds generally conta ined visual normal developed embryos, which germinated better than tho se from lighter seeds and gave normal plant development. Delayed picki ng increased the proportion of large seeds, suggesting that pollinatio n with irradiated pollen retards embryo development. From treatments z with irradiated pollen of poor quality more small seeds were harvested .