The effect on the biological control agent Mallada signata of trichomes of F1 Lycopersicon esculentum×L. cheesmanii f. minor and L. esculentum×L. pennellii hybrids

Abstract

The introgression of trichome-based host plant resistance of wild Lycopersicon species into L. esculentum may help reduce pesticide use in tomato production but its compatibility with biocontrol agents is largely unknown. The effect of trichome-based host plant resistance on the biocontrol agent, Mallada signata (green lacewing), was assessed for L. esculentum × L. pennellii and L. esculentum × L. cheesmanii f. minor hybrids. An intact leaf was isolated from the whole plant using Tangletrap to coat the petiole and 10 green peach aphids (Myzus persicae) were placed on the leaf surface. After 48 h, 10 M. signata were placed on the leaf. The numbers of dead, alive, and emigrating M. signata and M. persicae were recorded after a further 24 h. Differences in insect designations (i.e., dead, alive, and emigrating) between accessions were analysed and multiple linear regression was used to determine relationships between insect designations and the densities of each trichome type and leaf area. Within pooled data from both types of hybrid, M. signata mortality was greater on the hybrids of L. pennellii than on the L. cheesmanii f. minor hybrids. M. signata mortality was associated with high densities of type IV trichomes. When data were analysed separately for each type of hybrid, a relationship between types IV and VI trichomes and M. signata mortality was evident within L. cheesmanii f. minor hybrids though not within L. pennellii hybrids. Results suggest that the glandular trichomes of L. esculentum × L. cheesmanii f. minor and L. esculentum × L. pennellii hybrids negatively affect the biocontrol agent M. signata.