Location: Sunflower Research
2011 Annual Report
We evaluated herbicide-tolerant advanced canola breeding lines under field conditions for their reaction to Sclerotinia stem rot. Plots were inoculated twice with an ascosporic suspension (103 ascospores ml"1) and misted to stimulate disease development. Disease incidence ranged between 3 and 81% and severity between 0.3 and 3.6 (0-5 scale). Average incidence and severity for lines, 9023, 9024, 9091, and 9092 was 12% and 0.3, respectively. In contrast, the average incidence of the four commercial controls used in this study was 28% with a mean severity of 1.1. These lines are being advanced in the breeding program. A total of 144 Fa plants from the PI 169080 x Westar population were evaluated in replicated trials for their reaction to S. sderotiorum in greenhouse. Forty six plants produced a resistant reaction whereas 98 were considered susceptible. DNA from these plants has been extracted and sent for genotyping using Diversity Array Technology (DArT). The use of this technology will allow us to screen the materials with more than 3,200 markers and to locate them in a chromosome map. This will facilitate in great deal the identification of QTL associated with resistance. DNA from 282 B. napus accessions was extracted after the seedlings were evaluated for their reaction to S. sderotiorum using the petiole inoculation technique (PIT). Approximately one half of these accessions had been already identified as having some degree of resistance against S. sderotiorum in a previous project funded by the SI (Khot, 2006). DNA from these samples was genotyped using more than 3,200 DArT markers. While more than 1,200 polymorphic markers were detected, data analysis has not been finished yet. Resistant plants from this population have been self-pollinated. We intend to continue evaluation of these materials in the future. The development of double haploid lines from cultivar Topaz was delayed due to problems with contamination of lab media earlier in the year, DH lines from Topaz has resumed. Approximately 288 clones from a DH line produced by the cross between 458940 x Ames 26628 were developed. These two parental lines had been previously identified as resistant to S. sderotiorum. Clones were inoculated using six different methods and using two S. sderotiorum isolates, and petiole inoculation was the most reliable and consistent in detecting differences in resistance as well as differences between the isolates used. A similar study was conducted using DH lines derived from cv. Westar.