Drought resistance of 10 species or clones of apple rootstocks was assessed under potted cultural conditions. Cluster analysis of drought injury index and relative growth was employed to detect the resistance of the rootstocks to water stress. Results showed that the newly-bred clones of Luo-6 and Luo-2 held high resistance to drought stress, their shoot relative growth(RG)sustained 92.13% and 88.15% respectively under moderate water stress with a soil relative water content (RWC) of 40%~45%. Even after 24 ...