Abstract:

Dwarf mutant type was discovered during the investigation of wild pear resources in the
Yimeng Mountain Area，and the mutant shoots were grafted on adult trees in the experimental station of
Qingdao Agricultural University in 2009. The botanical characteristics，biological habits and the heritable
stability of dwarf property were observed. The results showed that the mutant tree was compact with very
short internodes of shoots，and obviously different from the general Pyrus betulaefolia. Moreover，the
dwarf property kept stable after transfer grafting for many times on the adult trees，and virology test
showed no obvious abnormality. Besides internodes，the villi of shoots，fruit shape，leaf，etc were obvious
difference as comparison with P. betulaefolia and P. calleryana，and preliminary could be confirmed as a
natural dwarf mutant type of the genus Pyrus，and named as‘PY-9’on the basis of field investigation
number. The discovery of this resource material，provided special genetic resources for the future research
on the pear dwarf mechanism and dwarf rootstock breeding.

Key words: Pyrus, dwarf mutant, evaluation