Glossy Leaf Wax and Plant Resistance to Insects in Brassica oleracea Under Natural Infestation

Abstract

The glossy cauliflower PI234599 has been shown by other authors to have resistance to three species of Lepidoptera, but the relationship between insect resistance and the glossiness of the leaf surface has been unclear. To examine this relationship in a broader range of Brassica oleracea L., five species of insect pests were counted under natural infestation on eight glossy genetic lines of broccoli, cauliflower, Brussels sprouts, collards, and kale; six lines reported to have reduced leaf wax; and ten varieties of the same crops with normal leaf wax. Glossy lines consistently had fewer imported cabbageworm, Artogeia rapae (L.), larvae and eggs and fewer cabbage aphids, Brevicoryne brassicae (L.), than other lines. Four of the glossy lines had low numbers of diamondback moth larvae, Plutella xylostella (L.), in all three plantings, but the other four performed differently in separate plantings. Surprisingly, a glossy kale with allelic genes for glossiness to PI234599 had poor resistance to diamondback moth. Glossy lines had the most Phyllotreta cruciferae (Goeze) in one spring planting, but there were no significant differences in the numbers of this species of flea beetle on various lines in the fall planting at the same location. This study identifies additional promising sources of insect resistance among glossy lines of B. oleracea, but further study is needed of the variability in resistance to diamondback moths and flea beetles over repeated plantings and among different glossy lines.