Effect of Bacillus mediated priming on different natural genetic variants of Arabidopsis thaliana

Abstract: In two feeding experiments Bacillus induced priming of plant defense was tested for its effect against the generalist insect pest Spodoptera littoralis. The main hypothesis for the study was that Bacillus induced priming would enable the plant Arabidopsis thaliana to defend itself better against this insect herbivore since this priming seems to involve jasmonic acid, known to be important for plant defense to insects. A secondary objective of the study was to examine if any differences in a primed defense capability could be seen between different natural genetic variants (ecotypes) of A. thaliana reflecting habitat differences in pest pressure. The methods used for plant cultivation and Bacillus inoculation were aimed at reflecting conditions that can be expected in an agricultural cropping system. This meant that all plants were cultivated in soil, and the feeding experiments were conducted with the plants growing intact in the soil system. Inoculation of plants was done with the Bacillus bacteria in its stress resistant spore form. A literature survey was performed to gather knowledge involving some of the more important concepts in plant defense against herbivores. The glucosinolate/myrosinase system as well as defense activation was studied in more detail. The study concluded that although Bacillus mediated priming was found to have an effect on some induced defenses in A. thaliana, no enhanced resistance against an insect herbivore was observed within the experiments conducted.