272Molecular and phenotypic characterization of near isogenic lines at QTL for quantitative resistance to Leptosphaeria maculans in oilseed rape (Brassica napus L.)

摘要

The most common and effective way to control phoma stem canker (blackleg) caused by Leptosphaeria maculans in oilseed rape (Brassica napus) is through the breeding of resistant cultivars. Specific resistance genes have been identified in B. napus and related species but in some B. napus cultivars, the resistance is polygenic (mediated by Quantitative Trait Loci), postulated to be race non-specific and durable. The genetic basis of quantitative resistance in the French winter oilseed rape 'Darmor', derived from 'Jet Neuf', has been studied in two genetic backgrounds (Pilet et al. 1998, 2001) and QTL stably involved in blackleg resistance across year and genetic backgrounds were identified. Near-isogenic lines (NILs) were produced in the susceptible background 'Yudal' for three of these QTL using marker-assisted selection. New molecular makers were developed through various strategies and mapped in these QTL regions. They were used to characterise the derived NILs for the length and homozygosity of the 'Darmor' introgressed segment. Different representatives of each NIL have been experimented in blackleg disease field trials and assessed for their level of crown canker in comparison to the recurrent line 'Yudal'. This work provides valuable material that can be used to study the mode of action of genetic factors for L. maculans quantitative resistance.