Analysis of genotypic differences in biochemical and physiological adjustments to N-deficiency and drought stress in potatoes (Solanum tuberosum L.) with consideration of yield components

Abstract

This work aimed at comprehensive phenotyping of starch potato cultivars in response to N-deficiency and drought stress at the morphological, physiological and biochemical level. For this purpose, 17 European potato cultivars were investigated in two years pot trials in a rain-out shelter with two N-levels and two water supply regimes. Additionally, a broad in vitro screening was performed to monitor specific traits under different N-levels in dependence of the genotype. Furthermore, out of these two contrasting genotypes were analysed in a proteomic approach to identify proteins associated with genotype specific responses to N-deficiency.

With regard to tuber and starch yield cv. Tomba proved to be comparatively tolerant and cv. Kiebitz rather sensitive under both, N-deficiency and drought stress. Other cultivars responded differentially depending on the type of stress. Nitrogen use efficiency generally increased under N-deficiency. Water use efficiency decreased under limited water supply, but was increased by increased N-supply. Biochemical and physiological parameters of leaves were analysed at two time points during a drought stress phase. The proline content increased under drought, while the N-supply level had an effect on the speed and extent of its accumulation. The content of total soluble sugars increased at short-term drought and dropped back at long-term drought, which was more pronounced at higher N-supply. The leaf water potential decreased rapidly under drought, however, significant osmotic adjustment was not detected. Correlations of biochemical or physiological parameters to agronomic traits were too weak to serve as markers for abiotic stress tolerance.

In vitro assays disclosed significant differences between cultivars in the ability to maintain biomass production, photosynthesis and N-metabolization under decreased N-supply. Furthermore, genotype dependent responses were detected regarding the root to shoot ratio, which was increased under N-deficiency in some specific cultivars.

The proteomic analysis revealed that 21 % of the detected proteins differed in abundance between the sensitive and the tolerant genotype. In control and N-deficiency conditions 19.5 % were differentially accumulated in the sensitive and 15 % in the tolerant genotype. Out of a total of 106 differentially abundant proteins, only eight were detected in both genotypes, which were mainly associated with general stress response. In the tolerant genotype, the determined high chlorophyll content was associated with an increase of respective catabolic enzymes. In particular, rubisco activaseshowed interesting modulations in dependence of genotypes and N-levels.

This dissertation was only published as a printed edition.