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Insect herbivores and arbuscular mycorrhizal fungi (AMF) often occur simultaneously on a host plant, altering plant morphological and biochemical traits and thereby not only affecting each other's performance, but also plant interactions with subsequent above- or belowground herbivores. Here, we investigate the combined effects of AMF and above- and belowground herbivory on plant productivity and performance of subsequent above- and belowground herbivores. We conducted a 3 × 2 full-factorial experiment with three levels of 'Herbivory (no herbivory, leaf herbivory, and tuber herbivory) and two levels of 'AMF inoculation' (no AMF inoculation and AMF inoculation) in the tuber-plant, potato (Solanum tuberosum). We showed that both AMF and tuber herbivory increased tuber biomass and tuber primary metabolites (protein, starch). Tuber herbivory reduced the performance of subsequent conspecifics feeding on leaves potentially via increased leaf levels of phenolics, α-solanine and α-chaconine. By contrast, it increased the performance of subsequent conspecifics feeding on tubers potentially via increased protein, however, only in plants inoculated with AMF. This indicates that the belowground facilitation among conspecific insects was contingent upon the presence of AMF. Leaf herbivory did not affect subsequent above- or belowground insect performance. These feedings improve our understanding of the ecological consequences of antagonists and mutualists interactions mediated by phytochemistry, especially for agroecosystems. [ABSTRACT FROM AUTHOR]

Understanding how host plant chemistry affects invasive insects is crucial for determining the physiological mechanism of host use and predicting invasive insect outbreak and damage on hosts. Here, we examined the effects of plant nutrition and defensive chemicals on host preference and performance of adults and larvae of the invasive potato tuberworm, Phthorimaea operculella (Zeller; Lepidoptera: Gelechiidae), on four native (Solanum tuberosum , Nicotiana tabacum , Datura stramonium , and Solanum lycopersicum) and three new (Solanum melongena , Physalis alkekengi , and Lycium barbarum) host plants. We found that adults preferred to oviposit on S. tuberosum and N. tabacum leaves and the soil around these native host plants over other hosts. Larvae performed well on S. tuberosum and N. tabacum , reaching higher pupa weight and having better survival. Larvae performed poorly on S. melongena , S. lycopersicum , P. alkekengi , D. stramonium , and L. barbarum , with lower pupa weight and lower survival. Solanum tuberosum and N. tabacum had higher leaf soluble proteins than other plants and lower leaf total phenolics than S. lycopersicum , D. stramonium , and L. barbarum. Moreover, carbon content and soluble protein were positively associated with larval survival, while defensive traits (lignin and total phenolics) negatively affected larval survival. These findings provide insights into understanding of biochemical mechanisms of interactions between invasive insects and host plants, indicating the importance of considering plant chemistry when assessing invasive insect host use and damage. [ABSTRACT FROM AUTHOR]

Simple Summary: Aboveground herbivory can affect belowground herbivore performance by changing plant chemicals. However, it is not clear how leaf feeding affects tuber-feeder performance in tuber-plants. We evaluated the effect of foliar feeding of the potato tuberworm P. operculella on the performance of conspecific larvae feeding on harvested tubers and measured the phytochemical changes in leaves, roots, and tubers. We found that aboveground P. operculella leaf feeding negatively affected the performance of conspecific tuber-feeding larvae, likely due to the increased α-chaconine and glycoalkaloids in tubers, suggesting that plant chemicals were reallocated among different tissues, with greater changes in metabolic profiles in leaves and tubers compared with roots. Thus, aboveground feeding by P. operculella during the growing season can change tuber resistance against the potato tuberworm during the warehouse storage of tubers. Conspecific aboveground and belowground herbivores can interact with each other, mediated by plant secondary chemicals; however, little attention has been paid to the interaction between leaf feeders and tuber-feeders. Here, we evaluated the effect of the foliar feeding of P. operculella larvae on the development of conspecific larvae feeding on harvested tubers by determining the nutrition and defense metabolites in the whole plant (leaf, root and tuber). We found that leaf feeding negatively affected tuber larval performance by increasing the female larval developmental time and reducing the male pupal weight. In addition, aboveground herbivory increased α-chaconine and glycoalkaloids in tubers and α-solanine in leaves, but decreased α-chaconine and glycoalkaloids in leaves. Aboveground herbivory also altered the levels of soluble sugar, soluble protein, starch, carbon (C), nitrogen (N), as well as the C:N ratio in both leaves and tubers. Aboveground P. operculella infestations could affect the performance of conspecific larvae feeding on harvested tubers by inducing glycoalkaloids in the host plant. Our findings indicate that field leaf herbivory should be considered when assessing the quality of potato tubers and their responses to pests during storage. [ABSTRACT FROM AUTHOR]