Transferring clubroot resistance from Chinese cabbage (Brassica rapa) to canola (B. napus)

Abstract

Clubroot, caused by Plasmodiophora brassicae, is one of the most important diseases of Brassica species worldwide, including vegetable and oilseed crops. A dominant clubroot resistance gene from B. rapa (Chinese cabbage) was previously fine mapped and molecular markers were developed in Chinese cabbage that could be used for marker-assisted selection (MAS) in other Brassica crops. To transfer this clubroot resistance gene to B. napus (canola), an interspecific hybridization was made between B. napus (canola) and B. rapa (Chinese cabbage). Subsequently, the F1 was backcrossed to the canola recurrent parent for three generations to produce BC1, BC2 and BC3 progenies. Using these populations, simple sequence repeat (SSR) markers flanking the clubroot resistance gene were used to perform MAS in canola. These molecular markers were then evaluated in 13 different canola and rapeseed quality genotypes in B. napus and B. rapa. These markers exhibited high reliability in identifying clubroot resistance in this diverse set of Brassica genotypes. Clubroot resistance also co-segregated with the SSR markers flanking the clubroot resistance gene in the BC3 and BC3S1. The segregation ratio of resistant and susceptible individuals in the BC3 supported the expected 1:1 ratio for the segregation of a single Mendelian gene. BC3S1 families with homozygous clubroot resistance were developed during this process, and should be valuable sources of clubroot resistance in B. napus breeding activities.