Results are presented from a comparative test of the photosynthetic apparatus (PSA) tolerance to abiotic stress (drought and high temperature (HT) in two potato cultivars and 10 breeding lines. The influence of drought and HT on the condition and functional activity of the PSA was studied by analyses of chlorophyll fluorescence characteristics of photosystem II (PS II) and plastid pigments content in the potato leaves. Plants were subjected to stress factors during the reproductive period (bud formation – flowering phases), which is considered particularly critical for potato plants.
It was established that the applied stress increased the initial (F0) fluorescence in dark adapted leaves and decreased the maximum (Fm) and variable (Fv) fluorescence. The quantum yield (Fv/Fm) of the PS II also decreased in stressed plants. The plastid pigments content was lower in the stressed plants. The conclusion was that the studied accessions possess different tolerance to drought and high temperature stress. The PSA efficiency of lines PC 595, E 102, Е 199 revealed a trend to higher tolerance, followed by lines E 68, D 68 and Е 136. The varieties Nadejda and Sante expressed a similar response to stressors. We consider them to be appropriate accessions for the potato breeding programme as far as drought and high temperature stress tolerance are concerned.