Variation in Trichome Types and Density Mediates Plant-Herbivore Interactions in Two Cucurbitaceae Members

Plant structural defenses such as trichomes and spines exert a significant selection pressure on insect herbivores. However, how species variation affects structural defense trait expression in closely related species is less understood. Through our studies, we tried to dissect the role of trichomes in mediating plant-insect interactions, in two non-model cultivated species in Cucurbitaceae: Lageneria siceraria, and Cucumis sativa family, and Trichoplusia ni as our major herbivore of interest. We observed that species differed in their attractiveness to different herbivores and their feeding behavior in common garden experiment. To tease apart structural and chemical defenses and their independent roles in these interactions, we first used a desktop electron microscope (SNE-4500 Plus Tabletop), to identify, quantify and measure trichome related traits including their morphology and density. We found that C. sativa has significantly lower number of trichomes as compared to L. siceraria, regardless of trichome type and leaf surface. We then followed this with manipulated diet experiments and found that trichomes from these two species differentially affected growth and development of T.ni, and also confirmed that trichomes from L. siceraria were also effective in repelling T.ni, a behavior we observed in common garden experiments. Taken together, we show that trichome variation is an effective defense strategy in L. siceraria against herbivores with consequences for their survival