Interaction of maize root associated fungi and the western corn rootworm

Abstract

Diabrotica virgifera virgifera, the western corn rootworm (WCR), is an invasive root feeding maize pest in Europe, which was accidentally introduced from the USA. The presented thesis is part of a German Research Foundation (DFG) project that was carried out in cooperation with Flavia Dematheis and Prof. Dr. Cornelia Smalla (Julius-Kühn Institute, Institute for Epidemiology and Diagnostics, Braunschweig, Germany). The thesis includes three different functional areas that were investigated: (1) Interactions between soil type and maize cultivar influencing WCR development (2) Interactions between WCR larvae and the root infecting plant pathogen Fusarium verticillioides (3) Interactions between WCR larvae and the mutualistic mycorrhiza Glomus intraradices We show that soil type did not have an effect on the suitability of a maize cultivar for WCR development, and WCR development significantly differed between maize cultivars that were considered to be susceptible. WCR larval feeding did strongly accelerate root colonization by the root infecting plant pathogen Fusarium verticillioides. Above ground colonization of the plant by Fusarium verticillioides was significantly increased by larval damage. Larvae are capable of transporting viable Fusarium verticillioides after having fed on colonized plants, but avoid moving to colonized plants. In addition the transported inoculum was not sufficient to induce colonization on non-colonized plants. The mycorrhiza Glomus intraradices retarded the growth of WCR larvae, but larval feeding did not influence mycorrhizal colonization. The results of the Braunschweig research group on the structure of fungal communities were taken into account and compared with the results reported in this thesis. Our results are discussed with regard to their relevance for plant health, plant protection, WCR ecology, biology and management.