By constraining a plant’s nutrient budget, variation in soil nutrient content can affect both the nutritional quality and the defense chemistry of plant tissues used as food for herbivores. Using young ‘Sour orange’ (Citrus aurantium) rootstock we examined how fertilizer concentration 1) affects mass and survival of larval sugarcane rootstock borer weevil (Diaprepes abbreviatus), and 2) interacts with root weevil feeding to affect plant protein concentration, and expression of enzymes associated with plant defense. The enzymes - chitinase, peroxidase, and b-1,3-glucanase - are among a group of proteins referred to as “pathogenesis-related” proteins because they are induced in pathological situations. Induction of these proteins has been associated with reduced herbivore performance in some studies. In our study well-nourished plants supported a greater total mass of larvae than did nutrient-stressed plants, but percent survival of larvae was similar across nutrient treatments. Hence, individual larvae were on average larger on well-nourished plants. While leaves and roots of well-nourished plants had generally higher concentrations of total proteins, they also had higher activity levels of chitinase and peroxidase, and roots had higher activity levels of glucanase. In this study, performance of the insect was enhanced by improved plant nutrition despite elevated levels of putative defense proteins.
Species 1: Coleoptera Curculionidae Diaprepes abbreviatus (sugarcane rootstalk borer weevil)
Species 2: Citrus aurantium (sour orange)
Keywords: plant resistance and environmental stress, pathogenesis-related proteins
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA