Variation of nitrogenous components in potato (Solanum tuberosum L.) tubers produced under organic and conventional crop management

The information related to protein and other nitrogenous components in organically produced potato tubers can be interesting for consumers with specific diets. Such information is still limited. Here we report results on the effects of organic and conventional production systems on accumulation of nitrogenous substances including total tuber protein and the nutritiously most important tuber protein, patatin, observed in five cultivars on two localities during three consecutive years. Organically produced potato tubers contained significantly lower content of total nitrogen, crude protein, nitrates and glycoalkaloids (α-solanine and α-chaconine). Protein content, patatin relative abundance in total tuber protein and patatin content in organically produced potato tubers were slightly lower than in conventional ones but the differences were not statistically significant. The cultivar and interactions between cultivars and other production factors affected considerably contents of crude protein, protein, glycoalkaloids and patatin relative abundance. The effect of cultivar on these nitrogenous characteristics was stronger for potatoes produced under conventional farming indicating the sensitive reaction of organically produced potatoes on less favourable agro-ecological production conditions. The results indicate that cultivar-specific genetic factors play the predominant role in the reciprocal interaction with other cultivation factors affecting the nitrogenous qualitative parameters of organically produced potato tubers. This should be considered to include primarily the cultivar in quality standards of organic farming. The late maturing cultivar Bionta exhibited high instability in tubers yield, total protein and patatin protein characteristics when produced under organic farming system, while the early maturing cultivar Karin reacted on the conditions of organic farming by an increase of the patatin content.