A STUDY ON SHORTENING THE JUVENILE PHASE OF APPLE SEEDLINGS

For accelerating the apple tree breeding process, a shortening of the juvenile phase of seedlings is very important.
Experiments were carried-out in attempt to solve the problem.
In 1982 foliar spraying of 3-and 4-year-old nonbearing apple seedlings with growth retardants were carried out in the field from late May to early June and the trunks were also girdled in late May.
Four treatments were employed:

1. succinic acid-2–2-dimethylhydrazide /B9/ at 2 000 ppm plus /2-chloroethyl/ phosphonic acid /ethephon/ at 1 500 ppm and with girdling;

2. B9 at 2 000 ppm plus ethephon at 1 000 ppm and with girdling;

3. only girdling;

4. control.

The results indicated that certain combinations of growth retardant and girdling significantly increased blooming, both of 3 year-old seedlings of ‘Qin Guan’ and 4-year-old seedlings of ‘Rall’ x /’Starkrimson’ + ‘Richared Delicious’/. B9 at 2 000 ppm plus -thephon at 1 500 ppm and with girdling was more effective the other treatments.
It induced 76 % of the 3-year-old seedlings to bloom for the first time.
The average number of flower clusters per tree increased 5-fold as compared with the control.
This treatment /1./ also induced 82 % of the 4-year-old seedlings to bloom.
The average number of flower clusters per tree increased 15-fold as compared with the control.
The main effect of the first treatment appeared to be increase flower production on trees that had already completed the juvenile phase.
Further research is needed to clarify this point.

Fruit Breeding

Z. Guo, G. Guo, S. Yan

https://doi.org/10.17660/ActaHortic.1988.224.17