Work

Segregating BC2F1 interspecific hybrids between Brassica napus and B. nigra reveal a major effect locus for blackleg resistance on chromosome B2

Year: 2026

Type: article

Abstract: Blackleg (Phoma, Leptosphaeria maculans ) is one of the most important diseases affecting rapeseed ( Brassica napus , 2n = AACC) worldwide. Although a number of major blackleg resistance genes have been identified in B. napus , finding novel sources of resistance is critical in dealing with this rapidly evolving fungal pathogen. Black mustard ( Brassica nigra , 2n = BB) is a highly resistant wild relative species for which at least one blackleg resistance gene has been described ( Rlm10 on chromosome B4), but which has been rarely investigated as a source of blackleg resistance for introgression breeding (probably because it is self-incompatible, heterozygous, difficult to hybridize with B. napus and until recently lacked the genetic and genomic resources available for the Brassica A- and C-genome species). We produced allohexaploid hybrids (2n = AABBCC) between B. napus and B. nigra followed by two generations of backcrossing to develop a BC 2 F 1 population segregating for inheritance of specific B-genome chromosomes from B. nigra . This population was phenotyped for blackleg resistance using a cotyledon test with blackleg isolate “JN2” ( AvrLm4-7 , 5–9 , 6 , 8 , 10 A-B , 11 , S-Lep2 ) and genotyped with B-genome chromosome-specific markers. Resistance segregated with the presence of chromosome B2 ( p < 0.0001). Future work will target the identification or production of introgression lines, and recovery of this genetic locus from the B genome in a rapeseed (2n = AACC) genomic background. Our work highlights the potential of B. nigra and Brassica wild relatives as sources of novel biotic stress resistances.

Source: Molecular Breeding

DOI: 10.1007/s11032-026-01690-5

Authors: Paula Vasquez-Teuber, Roman Gaebelein, Jessica L. Soyer, Thierry Rouxel, Jacqueline Batley, Annaliese S. Mason