Volatile emissiona by Brassica nigra HR+ (+) or HR− (−) plants in response to eggs of Pieris brassicae (PB) and Mamestra brassicae (MB) sampled at 24 or 72 h after oviposition.

aVolatile emissions are given in mean peak area ± SEM/g fresh weight of foliage divided by 105 with the number of replicates between brackets.*values with asterisk indicate significant differences in emission quantities between oviposition-induced B. nigra and uninfested control for each treatment (Mann-Whitney U-test).