Influence of different fertilization regimes on the composition of the phloem sap of tansy (Tanacetum vulgare L.) in the context of aphids´ feeding preference

Grako678 C3

From 01/2004 to 12/2007

Staff: Ewald Komor, Karlheinz Seifert, Wolfgang Völkl, Matthias W. Lorenz

Tanacetum vulgare (L.) (family Asteraceae) is a weed, which is found on many places especially on ruderal areas and along road sides. This lightly toxic plant is used by different species of aphids as a host plant. The aphids penetrate the leaves or the stem of the plant with their specialized mouth parts (stylet) searching for sieves tubes, and, when these were found, remain in this position and feed on phloem sap for extended period. This feeding behaviour is used for a method of phloem sap collection called stylectomy or aphid-technology. The stylet of the feeding aphid is cut by a heat pulse and the exuding phloem sap from the stylet stump is collected and analyzed. The aim of the project is to analyse the composition of phloem sap of tansy at different nutrition regimes, especially at different nitrogen fertilization levels. As a prerequisite of the project a reliable all-season plant breeding system is set up to assure a constant, standardized source of experimental plants for feeding tests. Seed germination from greenhouse plants shall be stablished as well as clonal propagation from rhizomes to obtain genetically identical plants. Plants will be grown under defined, standardized nutrient conditions in the greenhouse and the nutrient status of leaves and stems will be controlled. In addition amino acid analyses of field-grown plants together with soil sample analyses shall be made to compare the nutrient conditions at natural places of tansy with those of the experimental plants. The phloem sap collected with stylectomy will be analyzed with special emphasis on amino acids, which are thought to be a main determinant of aphids´ feeding preference. Electrical penetration graphs (EPG) are planned to examine the foraging behaviour on the plant, the searching time of the stylet and the duration of phloem sap feeding. Furthermore and the attractiveness of honey dew for ants on tansy plants of different nutrient status will be examined. The project is situated in the general context of plant-insect interaction and is specifically based on two previous GRAKO projects performed by S. Bauer and R. Wiedemann; (2001-2004).

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