|
|
|
| Effects of elevated ozone- and CO2-concentrations on the resistance pattern of two unequal susceptible potato- and barley-cultivars with regard to fungal parasites |
|
M. Pleßl, Ingrid Heiser, J. Habermeyer and E.F. Elstner
Institute of Phytopathology, Technical University of Munich, 85350 Freising-Weihenstephan, Germany
|
Our project deals with the question, whether an elevation of CO2 (from 400 to 700 ppm) and / or ozone (from ambient to "two-fold ambient") is resulting in a shift of resistance of potato infected with Phytophthora infestans. Therefore two cultivars of different susceptibility were selected: "Bettina" represented the tolerant cultivar, "Indira" was highly susceptible to P. infestans. An identical experiment concerning two barley cultivars went for barley infected with Drechslera teres. This symposium mainly concerns the potato-experiments. Growth parameters were included in the trial to elucidate differences in susceptibility because of different treatments.
Treatment of the susceptible potato variety "Indira" with 700 ppm CO2 for 4 resp. 8 weeks resulted in a slight increase in tuber mass. Ozone impaired the production of tuber mass for the cultivar "Indira". Elevated CO2 and first and foremost "two-fold ambient" ozone caused a slight decrease in above-ground biomass. The C/N-ratio was increased by 700 ppm CO2 due to a explicitly reduced nitrogen content. This observation was true for the tested potato- and barley-cultivars.
In order to examine the resistance pattern, potato-leaves were detached and infected with spore suspensions of P. infestans after 4 resp. 8 weeks of exposition in the climate chambers of the GSF. Elevated CO2 caused an increased tolerance of infections for "Indira". This effect was only visible as macroscopic symptom expression on the leave surfaces and was not reflected in the DNA pattern with real time PCR. "Two-fold ambient" ozone concentrations attenuated this increase in tolerance induced by elevated CO2.
"Bettina" pointed out a higher basic enzyme-activity of chitinases and glucanases, which are "pathogenesis related proteins" (induced by stress or pathogen attack). The induction of these PR-Proteins showed no remarkable differences between the two potato-cultivars. The induction of chitinases was delayed in variants with 700 ppm CO2 compared to variants with 400 ppm CO2. Yet the level of chitinase-activity was nearly identical in all variants at day 5 after infection.
It is concluded that the sensitive potato variety "Indira" utilized the increase in net-CO2 assimilation via an increased C/N-ratio as a signal for initiating tolerance reactions.
|
|
|
|
