Spring canola is susceptible to Sclerotinia stem rot (SSR) and fungicides are used to control disease in the field. S1 per se recurrent selection and greenhouse and field screening were utilized in order to improve resistance of spring canola to SSR. Due to an apparent lack of trait improvement in Cycles 1 to 4, Population T was opened to convergent introgression of new resistance sources and subjected to selection utilizing Field Limited-Term Incubation (FLTI) method. These changes resulted in trait improvement beginning in Cycle 5, gradually leading to a near complete shift towards resistant field reaction by Cycle 10. On a scale of 1 (highly susceptible) to 9 (completely resistant) for SSDIS (Sclerotinia sclerotiorum Disease Incidence Severity), the Population T mean increased significantly from 2.4 in Cycle 5 to 6.7 in Cycle 10. The improved lines have potential for use in developing hybrids with field resistance to Sclerotinia.