CHANGES IN PHOTOSYNTHETIC ELECTRON-TRANSPORT IN POTATO CULTIVARS WITHDIFFERENT FIELD-RESISTANCE AFTER INFECTION WITH PHYTOPHTHORA-INFESTANS

The estimation of field resistance of potato cultivars to Phytophthora infestans are usually carried out in expensive and time consuming fie ld experiments over several years. Therefore, a procedure is required for the fast and objective determination of qualitative and quantitati ve field resistance of new cultivars. This study correlated level of f ield resistance to P. infestans in leaf discs or leaflets of various p otato cultivars to characteristic changes of Chlorophyll-a fluorescenc e (CF) parameters F-m (maximal fluorescence) and F-v (maximal variable fluorescence). Two different inocula, both containing virulence genes 1-11 were tested. The results were achieved when leaf discs from gree nhouse or field plants were each inoculated with a P, infestans spore suspension and incubated for 24 h. In field measurements, comparable r esults were obtained 48 h after inoculation. The estimation of field r esistance by measuring specific CF parameters could be an economical a nd rapid procedure to reduce or substitute visual lesion assessment fo r determining cultivar field resistance.