1.3.10
CHANGES IN PLASMA MEMBRANE QUALITY AFTER RESISTANCE INDUCTION AGAINST POWDERY MILDEW IN BARLEY

H VON ALTEN and H SAILE

Institut für Pflanzenkrankheiten und Pflanzenschutz, Herrenhäuser Str. 2, D-30419 Hannover, Germany

Background and objectives
Treatments of winter barley plants of cultivar Mammut with B50 (a metabolite of a Bacillus subtilis strain) and Trigonelline induce resistance against the powdery mildew fungus (Erysiphe graminis DC f. sp. hordei), an obligate biotrophic pathogen. To establish the resistance response in plants, a time interval of 2-4 days is required. In connection with a reduced infection density (45-65% compared to untreated plants), impaired fungal nutrition on induced resistant plants is discussed.

Materials and methods
The plasma membranes of induced resistant barley leaves were extracted, and the lipid composition regarding the saturation of fatty acids was examined by GC. ATPase activity was measured according to [1]. Membrane potentials were quantified by electrophysiological methods.

Results and conclusions
An infection of barley with powdery mildew caused a decrease in the degree of unsaturation. Inducer applications prevented the pathogen-induced changes and led to an increase in the degree of unsaturation [2]. After mildew infection, the activity of plasma membrane ATPase and membrane potential in primary leaves was increased. In induced resistant plants these effects could not be measured; ATPase activity and membrane potential stayed at the level of healthy plants.

We conclude that the alterations described do influence the allocation of assimilates in plants, and especially transport through the extrahaustorial membrane which results in changed availability of nutrients for the mildew fungus. The reduced assimilate transport can reflect the impaired pathogen nutrition on induced resistant plants.

References
1. Koyro HW, Stelzer R, Huchzermeyer B, 1993. Botanica Acta 106, 110-119.
2. Gernns H, v. Alten H, 1996. Journal of Plant Diseases and Protection 103, 590-595.