How Cabbage Aphids Brevicoryne brassicae (L.) Make a Choice to Feed on Brassica napus Cultivars

Plant resistance to aphids might be present in different plant tissues, such as the epidermis, mesophyll and phloem, but not all of them play a key role in determining the feeding preference of aphids. In this study, electrically recorded feeding behaviors of cabbage aphids were combined with choice tests and microscopic observations to understand the feeding preference of cabbage aphids on oilseed rape cultivars. The choice tests showed that more cabbage aphids survived on ‘Qianyou18’, and less on ‘Zhongshuang11’, compared with the other cultivars. The results of the choice tests were paradoxical with the results analyzed from the general and mesophyll-associated variables. The thick upper epidermis with bushy long trichomes on the leaves of ‘Zhongshuang11’ delayed the first probe of the cabbage aphids. The duration of phloem-feeding was similar among the four cultivars although there were differences in the hindrance of the mesophyll. However, salivation was increased when the aphids fed on ‘Zhongshuang11’, further indicating that the leaf’s physical properties could be important for aphid feeding preference on the four cultivars.