Research On Haploid Breeding Technique In Apple

Haploid breeding is a technology that through parthenogernesis or androgenesis to induce haploids, and then quickly obtain normal homozygous by chromosome doubling. Haplid breeding can selecte new varieties in a short time. This study mainly concentrated on anther culture and pollen irradiation to discuss apple haploid breeding technology.In the study of apple anther culture, many factors effected callus and embryoid induction, such as genotypes, pretreatment time, sucrose concentration, hormone combination, etc.11 apple varieties were used to disscuse those factors effect on anther culture in the single factor test and orthogonal test. And then the system of apple anther culture was established. The results showed that:1. Different genotypes had significantly effect on anther culture ability. The embryoid induction of ’Zhuguang’ was highst, which was 34.3%, followed by ’Redstar’.2. The optimum time of low temperature pretreatment was about 20-32 d for embryoid induction.3. It was significantly increase the rate of ’Redstar’ embryoid induction when the sucrose concentration was 5%.4. The optimum hormone combination of anther culture was 2.0 mg/L 6-BA +0.1 mg/L NAA.5. The system of apple anther culture was established:Embryoid induction medium:N6+2.0 mg/L 6-BA+0.1 mg/LNAA+0.3%AC+5%Sucrose+0.75% Agar; Embryoid differentiation medium:MS+1.0-5.0 mg/L 6-BA+0.1-0.3 mg/LIBA.6.22 lines were obtained through apple anther culture:’Qianqiu’10 lines, ’Fuji’7 lines,’Danxia’3 lines, and’Gala’2 lines. The DNA ploidy of regeneration plants was analyzed by flow cytometry.The results indicatedthat all of the plants were diploidy except that 2 triploid of’Qianqiu’,1 tetraploid of ’Qianqiu’ and 1 tetraploid of ’Fuji’. The ploidy of ’Danxia’ and ’Gala’ couldn’t be analyzed because the plants were too small.Pollen irradiation technique has been an important way to induce parthenogenesis in situ in apple. To increase haploid induction rate using this technique, a deeper understanding of irradiated embryo development process is required. In this study,’Fuji’ and ’Olin’ were pollinated with’Sansa’ pollens irradiated by 500 Gy y-rays, then the processes of fertilization and embryogenesis were observed. The results showed that irradiation treatment can reduce fruit set rate, decrease fruit size, and the seeds are abnormal. Compared with control, irradiation had no significant difference in pollen germination, pollen tube growth and early embryonic development. But the young embryos stopped developing at 20 days after pollination, and disappeared entirely at 40 days. It means that the optimum stage of immature embryo culture is on 20 days or so after pollination. The results provide a basis for the establishment of parthenogenic system of ’Fuji’ and ’Olin’.