Tritrophic relationships among tomato cultivars, the rust mite, Aculops lycopersici (Massee) (Eriophyidae), and its predators

Abstract

Trichome-mediated defence in wild and cultivated tomato cultivars has been extensively studied against some mite species for several decades. Previous studies have shown that this mechanism negatively affects phytophagous mites and their predators. To better explain the tritrophic relationship of tomatoes, the interactions between population densities of the tomato rust mite, Aculops lycopersici (Massee) (Acari: Eriophyidae), and its predators on the tomato cultivars, namely, Dora, Etna, Grande, H2274, Jana and M1103, and the trichome densities of these cultivars were investigated in both a climatic room and an organic tomato field from 2014-2015. Under both controlled and field conditions. the A. lycopersici population density was significantly higher in the stake tomato cultivars, Jana and Etna, than in other tomato cultivars. When the tomato rust mite's population density was the highest during mid-August and mid-September in the tomato field, the population density of the predator species. Tydeus kochi Oudemans (Tydeidae), showed a similar population pattern and significant positive correlation with the A. lycopersici density. However, density of this predator mite was significantly lower than that of A. lycopersici over the entire season. Remarkably, the glandular trichome type VI density was significantly higher in the stake cultivars than other cultivars. In contrast, significantly fewer glandular trichomes were found in the indeterminate tomato cultivars, Grande and H2274, which had fewer tomato rest mites and larger tydeid mite predator densities. These results support the hypothesis that trichomes provide excellent shelter for tomato rust mites and are obstacles for its predator mites. However, the population density of the insect predator, Macrolophus sp., was not affected by the trichome density or tomato cultivar, but its population density was not significantly correlated with that of the A. lycopersici population.