Untersuchungen zum Einfluss des Wurzelendophyten Piriformospora indica auf das Wachstum von Hordeum vulgare, die Resistenz gegen Blumeria graminis f.sp. hordei und die Genexpression in den Blättern

The plant root colonizing fungus Piriformospora indica was isolated 1997 from the spore of an AM-fungus in the Indian Thar desert. Growth-promoting properties of this endophytic fungus were observed in several plant species. Goal of the present work was to analyse the interaction of P. indica and Hordeum vulgare in detail and to characterize systemical effects on the shoot. Colonization of the roots with P. indica under greenhouse-conditions leads to significant plant growth promotion. Potculture experiments under outdoor conditions showed an earlier shifting of the spikes, an elevated amount of ears and an increase of 1.9 – 11 % in grain yield in three different cultivars of barley. Advices about an increase in the rate of photosynthesis and an increased chlorophyll content in leaves of colonized plants which could be found by analysis of subtractive cDNA-libraries could be confirmed. Furthermore the influence of root colonization on the resistance of the plants against the biotrophic leaf pathogen Blumeria graminis f. sp. hordei (Bgh) was evaluated. Macroscopically, an increased resistance of the colonized plants could be shown, which is based on increased penetration resistance as cytological experiments revealed. The detected induced resistance was associated with a higher disposition for a faster and more effective activation of the cellular plant defence. First gene expression analyses showed that known systemic induced resistance pathways of plants seemed not to be involved and that an activation of the antioxidative system could to play an important role. Hybridisation experiments performed using a cDNA-macroarray and the 22K barley1 GeneChip® (Affymetrix, Santa Clara, USA) identified relatively low amounts of differentially expressed genes in the leaves of colonized plants. Real-time PCR expression studies confirmed a higher induction of two putative receptor kinases in leaves of P. indica-colonized plants 12 h after Bgh-inoculation. This could indicate that P. indica induced resistance is due to an earlier recognition of the pathogen.