Physiological Response to Nitrogen Deficiency Stress of in vitro Grown Potato Genotypes

Increasing nutrient use efficiency is an important aspect in sustainable plant production in order to optimize the use of resources and minimize environmental pollution. Our investigations aim at the identification of genotypic differences which will allow analyzing specific components of nitrogen use efficiency in potato. In addition to characterizing a set of cultivars under field and greenhouse conditions an in vitro culture system with four different nitrogen levels was established in order to investigate if specific components of nitrogen use efficiency can be assessed under such conditions. For this purpose shoot tips were grown fixed in perforated stainless steel plates in 500 ml glas vessels with 50 ml liquid culture medium. The nitrogen levels of the media corresponded to full, 1/2, 1/4 and 1/8 of the original MS concentration, i.e., 60, 30, 15 and 7.5 mmol/L. Specific morphological parameters were recorded within three weeks of culture and nitrogen uptake and assimilation was analyzed. The vegetative development of plantlets proved to be differentially affected by a reduction of nitrogen in the culture medium and varied with the genotype. Furthermore, determination of nitrogen withdrawal from the culture media as well as analysis of crude protein content in shoots and roots allowed discrimination among genotypes with respect to nitrogen uptake and utilization capacity.