Koscielny C. B. and Gulden R. H. 2012. Seedling root length inBrassica napusL. is indicative of seed yield. Can. J. Plant Sci. 92: 1229-1237. Recent studies have shown relationships between root growth and development and seed production potential in some crops; however, little is known about this relationship in Brassica napus. Field and growth room experiments were conducted to determine the relationship between root parameters up to the four-leaf stage and seed yield among a group of four open-pollinated and four hybrid B. napus genotypes with different yield potential. In the field studies, root length was the best indicator of seed yield at the one- to two-leaf and the three- to four-leaf stages of development, and was one of the most consistent parameters among sites and years. Poor ability to recover fine roots from field soils at the cotyledon stage contributed to the relatively poor relationships between root parameters and seed yield compared with shoot parameters at this developmental stage. The growth room study clearly showed that root length is an excellent measure of seedling vigour and an indicator of seed yield as early as 7 d after imbibition. These studies demonstrate the importance of early root development in canola and its potential as a screening trait for seed yield in breeding programs.