Development of spring canola (Brassica napus L.) resistant to stem rot (Sclerotinia sclerotiorum (Lib.) De Bary). [Doctoral dissertation] | Stvaranje genotipova uljane repice (Brassica napus L.) sa otpornošću prema beloj truleži stabljike (Sclerotinia sclerotiorum (Lib.) De Bary). Doktorska disertacija

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 green house/field screening were utilized in order to improve resistence of spring canola to SSR. Due to an apparent lack of trait improvement in Cycles 1 to 4, the Population T was opened to convergent introgressions of new resistance sources and subjected to selection utilizing Field Limited Term Incubation (FLTI) method. These changes resulted in initial trait improvements in Cycle 5, gradually leading towards near complete shift towards resistant field eaction in Cycle 10. On the scale 1 (highly susceptible) to 9 (completely resistant) for SSDIS parameter (Sclerotinia sclerotiorum Disease Incidence Severity), Population T mean increased from 2.4 for Cycle 5 to 6.7 for Cycle 10. One selected S1 line from Cycle 8 was stabilized via Doubled Haploid Method to generate a homozygous source of resistance. That Doubled Haploid (DH) source of resistance was crossed with a susceptible DH line. Their F1 was used to develop a double haploid population of 186 lines. The first canola hybrid with improved field resistance to SSR, 45S51, was registered in 2008 and the second, 45S52, was registered in 2010. SSR testing was conducted in three field scenarios from 2007-2010 across geographies/locations. Large scale on farms trials, where resistant hybrids were tested alongside susceptible canola products, was grown under natural field conditions. Data on disease incidence and disease severity were collected from which a disease index calculation SSFS (Sclerotinia sclerotiorum field severity) was performed. Large scale on farms trials over four years in Western Canada indicated a is greater than 50% overall reduction of SSFS in 45S51 vs. susceptible canola products. Field resistance was a function of reduced disease incidence and disease severity in the ratio 3:1 relative to susceptible check. While 45S51 field resistance did not match efficacy of fungicide control in the fiald, 45S52s field resistance was notably higher. The best control of Sclerotinia was attained by applying fungicide on products with improved Sclerotinia resistance. The introduction of 45S51 and 45S52 has provided farmers with a new tool to manage SSR in North America.