General (polygenic) resistance of plant hosts to an attack by a range of pathogens is an important feature of plant defense responses against the infection. In search of biochemical markers defining this resistance, cell suspensions derived from leaves of potato (Solanum tuberosum L .) cvs. Tarpan and Bzura that are polygenically susceptible and resistant to Phytophthora infestans, respectively, were inoculated with culture filtrate (CF) of the fungus. Cell suspension of Tarpan responded to CF treatment by a higher extracellular alkalinization and more significant reduction in their viability and growth than those of the Bzura cultivar. The stimulation of phenylalanine ammonia-lyase (PAL ) activity but not of β-1,3-glucanase, was significantly higher in CF treated Bzura cells than in Tarpan ones. The obtained results suggest that sensitivity to the fungal toxins and variation of PAL activity may represent useful markers for the evaluation of polygenic resistance in potato.

Soybean β-1,3-endoglucanase represents a model system for studies on early plant re­sponses to infection by fungal pathogens, and it has been implicated in the release of elicitors from fungal cell walls. In the present study, potato plants were transformed with the soybean β-1,3-endoglucanase cDNA via Agrobacterium delivery system. The transfer of the gene into potato genome was confirmed by (i) PCR amplification, (ii) Northern blot analyses, and (Hi) an increase in the activity of β-1,3-endoglucanase in transgenic plants. The transformation resulted in an increased resistance of selected transgenic plants to infection by Phytophthora infestans, an important pathogen.