Evaluation of nitrogen efficiency associated traits of starch potato cultivars under in vitro conditions

Genotype dependent responses to N-deficiency were investigated in vitro as well as in pots grown in a rain-out shelter with a set of 17 potato cultivars with the aim to identify genotypic differences in traits associated with nitrogen uptake and utilization and to compare results obtained in the two test environments. In vitro plantlets were grown under four nitrogen (N) levels (60, 30, 15 and 7.5 mmol/l) for 18 days and their respective traits were assessed after 7, 11, 14 and 18 days of culture (DoC). Considerable differences between genotypes were identified as early as seven DoC regarding N uptake, biomass production, root percentages of the total plant fresh and dry matter as well as chlorophyll (SPAD values) and crude protein concentrations. Significant differences were obtained for total biomass production between the 60, 30 and 15 mmol/l N-level as well as genotypic differences. Furthermore, significant variation between cultivars was identified for traits associated with efficient nitrogen use, e.g. the ability to maintain photosynthesis and N metabolization under N limitation as well as increased root development. No direct correlation was found between biomass production under in vitro conditions and tuber yields determined in pot trials. However, the stability of the plant performance under N-deficiency in the in vitro system as expressed by the membership function value of stress tolerance calculated from 11 traits correlated to the stability of the tuber yield of cultivars grown under limited N supply in pot trials (r = 0.70). The experimental system is thought to be useful for pre-screening of germplasm and investigations of physiological processes associated with nitrogen use efficiency.