AbstractSynthetic lines ofBrassica napuswere derived by combining the genomes ofB. atlanticaandB. oleraceavar.alboglabra, which were respectively resistant and susceptible to foliar infection byLeptosphaeria maculans, with a susceptible line ofB. rapa.Resistance was expressed in the synthetic lines containing the genome ofB. atlantica.The high levels of alkenyl glucosinolates which occur in leaves ofB. atlantica, and which have been implicated in disease resistance, were also expressed within the synthetic lines, although the dominant glucosinolate had changed from sinigrin to glucobrassicanapin. Disease resistance and glucosinolate profiles did not co‐segregate in F2progeny from crosses between the synthetic line