Shortening of the juvenile period in apple breeding

Summary

A very important aim for the acceleration of the breeding progress in apple is the development of methods for shortening the juvenile period. The period from sowing the seeds to the first bloom of the seedlings can take from 5 to 12 years. Only then we can begin with the complete evaluation of the progenies. Various cultivation methods were considered at the Pillnitz Institute. The basic idea is to grow the seedlings rapidly from the germination stage to the change from the juvenile to the adult stage. The best method appeared to be cultivation in the greenhouse under 16 hours light per day. At a minimum height of 180 cm graftsticks of each seedling were cut and grafted in April in the field on M9 rootstocks with Hibernal interstem. This way the growth was controlled and blossoming began earlier. Fruit size was normal and not smaller as on M 27. A few grafted seedlings began to blossom in the year of grafting. In the second year after grafting 20–25% blossomed, in the third year 65–85%, and in the fourth year nearly 95%. This high rate of blossoming seedlings enabled the completion of selection for all the important breeding objectives including the resistance to scab, mildew and fire blight within 6 years after sowing the seeds.