果树杂交育种中的一大难题,是实生苗童期长,结果晚,影响早出成果,快出成果。据国外报道和我们的实践经验,栽培苹果的童期一般为8—9年,即从播种算起需8—9年才开始成花结果。因而,造成苹果育种周期过长,不仅浪费时间,也不容易育成品种。果树育种工作者,为了缩短童期,曾进行多方面的研究。现已证明,童期除受 One of the major problems in fruit tree hybrid breeding is the fact that the seedling is of longer duration and the result is too late, which will affect the early results and quicken the fruits. According to foreign reports and our practical experience, childhood cultivation of apples is generally 8-9 years, which takes 8-9 years from planting to begin to bear fruit. Thus, causing apple breeding cycle is too long, not only a waste of time, it is not easy to breed varieties. Fruit tree breeding workers, in order to shorten the period, conducted a wide range of research. It has been proved that, in addition to childhood