Abstract: The effects of exogenous chromosomes on root morphology were studied with the disomic substitution series of Triticum aestivum L. cv. Chinese Spring-Lophopyrum elongatum (Host) A. Löve. Scanner-based image analysis was used to investigate total root length, surface area, mean diameter, and number of root per plant. The fractal dimensions of young root systems were also calculated. Compared with Chinese Spring, there were fewer roots per plant in 3E^e, 5E^e, and 7E^e substitutions and larger total root length and surface area in 1E^e, 2E^e, and 4E^e substitutions, indicating that genes associate with the above characteristics on the corresponding chromosomes respectively. But the genes controlling average diameter were found on every chromosome of L. elongatum. The fractal dimension of seedling root systems was significantly correlated with the above 4 root parameters included in root growth models (0.757**≤r≤0.845**). It is suggested that the fractal dimension can be used as an integrated index for summarizing root morphological characteristics of Chinese Spring and its substitutions after further studies.

Key words: Wheat, Lophopyrum elongatum, Exogenous chromosome, Substitution, Root characteristics