Possible effects of leaf tissue characteristics of oilseed rape Brassica napus on probing and feeding behaviors of cabbage aphids Brevicoryne brassicae

Obstacles in different tissue layers of leaves can influence aphid feeding behavior and host preference. In this study, we examined the feeding behaviors of cabbage aphids Brevicoryne brassicae (Linnaeus) (Hemiptera: Aphididae) on the five oilseed rape cultivars with varied levels of aphid susceptibility using the electropenetrography (EPG) technique. The leaf anatomical structures of the five oilseed rape cultivars were also analyzed using the microscopical observations. The results showed that the cabbage aphid feeding behaviors varied among the five cultivars. On ‘Dehezayou8’ which had the highest aphid population in the field, the cabbage aphids showed significantly shorter non-probing time to the first phloem contact, shorter duration of the no phloematic phase, and longer average probing duration than those on ‘Zhongyou821’ which showed the least aphid population. In the mesophyll of ‘Dehezayou8,’ the cabbage aphids made significantly fewer brief probes and spent a shorter time in penetrating the mesophyll cells than on ‘Zhongyou821.’ In the phloem, the aphids on ‘Dehezayou8’ secreted less saliva and ingested more sap than those on ‘Zhongyou821.’ On ‘Dehezayou8,’ the aphids took the shortest time to first penetration than they did on the other cultivars. ‘Dehezayou8’ had relatively thin upper epidermis and rare short trichomes, which might have facilitated the aphid infestation. Our results suggested that the leaf tissue characteristics of oilseed rape cultivars, such as epidermis thickness, trichomes, and the factors from mesophyll and phloem could be associated with aphid feeding preference and therefore aphid population in the field.