Introgression of Brassica rapa subsp. sylvestris Blackleg Resistance into B. napus
Blackleg is one of the predominant diseases of canola (Brassica napus). It is caused by a fungal pathogen called Leptosphaeria maculans. To address this problem, Fengqun Yu from Agriculture and Agri-Food Canada and other researchers transferred two blackleg resistance genes (LepR1 and LepR2) from B. rapa subsp. sylvestris (BRS) into canola through interspecific hybridizations. They analyzed the microsatellite markers in two backcross populations (WT3BC1 and WT4BC1) which showed that segregation fit a 1:1 ratio for BRS and non-BRS alleles.
The team used two L. maculans isolates (WA51 and pl87-41) to differentiate plants carrying resistance genes LepR1 and LepR2. They found that only 4.0 and 16.6% of the plants were resistant to isolates WA51 and pl87-41, respectively, in the WT3BC1 population, while 17.9 and 33.3% of the plants were resistant to these isolates, respectively, in the WT4BC1 population. Based on cotyledon resistance and marker-assisted selection (MAS), BC1 plant WT4-4, which carried a resistance gene similar to LepR1 (designated as LepR1′) and BC2S1 plant WT3-21-25-9, which carried LepR2′, were identified.
The resulting plants were successively backcrossed with B. napus. They used MAS in every generation to decrease non-resistance alleles related to the BRS genome and to recover the complete complement of C-genome chromosomes. This led to the formation of highly blackleg resistant B. napus lines.
The research paper is available at http://www.springerlink.com/content/b37u344048j14716/.
This article is part of the Crop Biotech Update, a weekly summary of world developments in agri-biotech for developing countries, produced by the Global Knowledge Center on Crop Biotechnology, International Service for the Aquisition of Agri-Biotech Applications SEAsiaCenter (ISAAA)