Abstract The use of nitrogen in nutrient media is essential for growth and helps identify highly productive media for potato (Solanum tuberosum L.) micropropagation and adventitious shoot formation. Three potato cultivars (Agria, Marfona and Savalan cultivars) were examined for their growth response with medium containing four different levels of KNO3 (1, 1.25, 1.5 and 1.75 times as much 1.9 g l-1) and NH4NO3 (1, 1.25, 1.5 and 1.75 times as much 1.65 g l-1). The morphogenic responses of cultivars were evaluated via measurement of root length, number of roots, shoot length, number of shoots and number of nodes per plantlet. Results indicated that the cultivars differed in their response to nitrogen source types and different concentrations. The results of both KNO3 and NH4NO3 experiments indicated that N3C1 and N3C2 (2.85 g l-1 KNO3 and 2.475 g l-1 NH4NO3 in Agria and Marfona, respectively) had the longest shoot length. Cultivars Agria and Marfona at 2.375, 2.85 and 3.325 g l-1 KNO3 produced the shortest root length, but cultivar Savalan in all KNO3 levels had the highest root length. Our findings indicated that the third concentration of both nitrogen sources (KNO3 and NH4NO3) were better than other nitrogen concentrations in all cultivars for number of shoots and number of nodes. Therefore, nitrogen source media should have significant utility for shoot or other important traits in potato in vitro culture conditions.
